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Imagine a world without seed dispersers: A review of threats, consequences and future directions
Abstract
Seed dispersing animals, ranging from small insects to large mammals, provide a crucial service for a large number of plant species worldwide. However, a decline in dispersers due to direct and indirect threats leads to disruptions of seed dispersal processes. As disperser species are differently susceptible to these threats, consequences for ecosystems are hard to predict. Impacts range from hampered regeneration of plant species to shifts in communities and a decline in ecosystem function. Here, we review these threats as well as expected consequences for communities and for the entire ecosystem. We further introduce options to protect dispersers and consider future research directions.
... Animal driven seed dispersal (i.e., zoochory) is an important ecosystem service that influences the composition and genetic structure of plant populations at local and landscape scales (Farwig and Berens, 2012;Mason et al., 2022;Wang and Smith, 2002). This mutualism is vulnerable to asymmetrical effects of climate change as participating plants and animals respond to disturbances in different ways (Mokany et al., 2014). ...
... Also, shifts in dispersal mutualisms due to biological invasions of competing vectors can cause cascading shifts in plant communities and associated ecosystem functions (Christian, 2001;Traveset and Richardson, 2006). Species specialized to geographic areas or diets appear to be more vulnerable to experiencing negative population or behavioral impacts from changes (Brook et al., 2008;Davies et al., 2004;Farwig and Berens, 2012) and potentially reducing their relative contributions to interactions. Shifts in the relative contributions of vectors can alter the dynamics of the seed dispersal process (González-Varo et al., 2018;Schupp et al., 2010;Mason et al., 2022), especially when functional redundancy within a system is low (Mouillot et al., 2013;Valiente-Banuet et al., 2015). ...
... Increasing prevalence of extreme weather worldwide due to climate change (Seneviratne et al., 2021) creates a potential for broad impacts as these stochastic events affect species and their interactions. These events do not occur in a vacuum either, other aspects of global change, such as urbanization, are disrupting ecosystems simultaneously and can interact with climate change factors to affect important processes like seed dispersal (Zhou et al., 2013) and drive community shifts in complex ways (Brook et al., 2008;Farwig and Berens, 2012;Tylianakis et al., 2008). It is therefore important to continue to build an empirical understanding of how important ecological processes are affected by extreme weather and other elements of global change moving forward. ...
Anthropogenic climate change is contributing to an increase in the frequency of extreme weather events. These extreme events may affect interactions in mutualisms that provide key ecosystem functions, especially when the event is rare for a given system and participants are differentially affected. The tropical hardwood hammocks of Key Largo, Florida, USA are inhabited by a highly specialized endangered rodent, the Key Largo woodrat (Neotoma floridana smalli), which may be an important seed disperser of many native fleshy-fruited plant species. Other potential mammalian dispersers are generalist omnivores, northern raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana), that are less selective. We sought to demonstrate that extreme climate events could alter seed dispersal mutualisms by differentially affecting fruit preference of potential dispersers. We designed a replicated cafeteria-style experiment across the entire range of the Key Largo woodrat with fruit from sixteen native plant species and simulated an extreme climate event by exposing half of the fruits to sub-freezing temperatures. Freezing temperatures are rare in this tropical environment, but increased frequencies of these types of extreme events are predicted with climate change. Using camera traps, we monitored the removal of fruit and seeds by woodrats and the generalist consumers, predicting that changes in fruit quality resulting from exposure to sub-freezing temperatures would reduce preference by the more specialized woodrat relative to its generalist consumers. Indeed, exposure to subfreezing temperatures decreased the probability of fruit and seed removal by woodrats while generalist consumers preferentially removed more of the fruits and seeds exposed to sub-freezing temperatures. These data provide evidence that extreme climate events may affect species preferences for food asymmetrically, which may shift the dynamics of seed dispersal mutualisms. Over time, increasing frequencies of extreme weather events could indirectly affect communities and ecosystem services by shifting interactions between organisms.
... Animal driven seed dispersal (i.e., zoochory) is an important ecosystem service that influences the composition and genetic structure of plant populations at local and landscape scales (Farwig and Berens, 2012;Mason et al., 2022;Wang and Smith, 2002). This mutualism is vulnerable to asymmetrical effects of climate change as participating plants and animals respond to disturbances in different ways (Mokany et al., 2014). ...
... Also, shifts in dispersal mutualisms due to biological invasions of competing vectors can cause cascading shifts in plant communities and associated ecosystem functions (Christian, 2001;Traveset and Richardson, 2006). Species specialized to geographic areas or diets appear to be more vulnerable to experiencing negative population or behavioral impacts from changes (Brook et al., 2008;Davies et al., 2004;Farwig and Berens, 2012) and potentially reducing their relative contributions to interactions. Shifts in the relative contributions of vectors can alter the dynamics of the seed dispersal process (González-Varo et al., 2018;Schupp et al., 2010;Mason et al., 2022), especially when functional redundancy within a system is low (Mouillot et al., 2013;Valiente-Banuet et al., 2015). ...
... Increasing prevalence of extreme weather worldwide due to climate change (Seneviratne et al., 2021) creates a potential for broad impacts as these stochastic events affect species and their interactions. These events do not occur in a vacuum either, other aspects of global change, such as urbanization, are disrupting ecosystems simultaneously and can interact with climate change factors to affect important processes like seed dispersal (Zhou et al., 2013) and drive community shifts in complex ways (Brook et al., 2008;Farwig and Berens, 2012;Tylianakis et al., 2008). It is therefore important to continue to build an empirical understanding of how important ecological processes are affected by extreme weather and other elements of global change moving forward. ...
... La frugivoría, así como los procesos ecológicos derivados como la dispersión y depredación de semillas son de vital importancia en los bosques tropicales, debido a que entre el 70 y el 90 % de las plantas leñosas dependen de un animal para dispersar efectivamente sus semillas (Farwig & Berens, 2012;Jordano, 2014). Debido a la alta diversidad tanto de plantas como de animales frugívoros en el trópico, las relaciones entre ellos suelen ser complejas, donde cada especie involucrada desempeña un papel diferencial en el resultado neto del proceso a nivel comunitario (Fricke et al., 2018;Lázaro et al., 2019;Messeder et al., 2020); mientras que a nivel ecosistémico la categorización de estas especies de acuerdo a su papel funcional, puede ser importante para establecer prioridades de conservación a nivel específico para el mantenimiento de los procesos ecológicos (Whittaker & Cottee-Jones, 2012). ...
... Tipo de pulpa El tipo de pulpa está asociado al síndrome de dispersión de las semillas. En el trópico más del 80 % de las plantas con frutos carnosos sus semillas se dispersan a través de vectores animales (Farwig & Berens, 2012;Jordano, 2014) Se establecieron cuatro categorías según el tipo de pulpa. i) arilo: donde la parte carnosa corresponde a partes distintas al pericarpio; ii) carnosa: en los que el pericarpio es jugoso, carnoso y rodea a las semillas; iii) fibrosa: con abundantes estructuras fibrosas en el pericarpio; iv) seca: con poco contenido de agua en el pericarpio (< 50 %) ...
Introducción:
La frugivoría es un proceso ecológico determinante para la estructuración y regeneración de los bosques. En los trópicos, donde la diversidad de plantas y animales frugívoros es alta, las relaciones interespecíficas son complejas y requieren estudio.
Objetivo:
Identificar las especies de plantas ecológicamente importantes en dos redes de interacción, y el papel de los rasgos funcionales de los frutos en esas interacciones en un bosque seco.
Métodos:
Recolectamos 10 frutos por planta de 10 plantas de cada especie de interés en un bosque seco colombiano, calculamos el índice de importancia de las plantas a partir de la relevancia de aves y mamíferos frugívoros en la estructura de las redes. Esta relevancia se relaciona directamente con el potencial del animal como dispersor efectivo de semillas. Utilizamos modelos lineales generalizados para estimar el tamaño, color, estrato, y tipo de pulpa, en el índice.
Resultados:
Las plantas más importantes son especies de los géneros Miconia, Ficus, Cecropia, Bursera, Casearia y Trichilia, también identificadas como recursos importantes para los frugívoros de los trópicos en otros estudios. Las plantas con frutos carnosos, rojos y de menor tamaño son los mejores para dispersores de semillas. El índice de importancia de las plantas tiene alta variación; esto sugiere que un conjunto de especies frugívoras beneficiadas por cada especie de planta tiene una contribución diferenciada en procesos ecológicos derivados de la dispersión de semillas.
Conclusiones:
Programas de restauración para este tipo de bosque tropical seco debería incluir una variedad de plantas, incluyendo especies con frutos pequeños, rojos y carnosos.
... dispersal is a crucial mutualistic interaction for many plants, as the transport of seeds to new sites drives metapopulation dynamics, decreases intra-specific competition and lowers predation pressure on seedlings, in turn increasing germination and recruitment success [21][22][23][24][25] . The loss of many large frugivores from island communities in particular puts native large-seeded plants at risk of extinction, as the remaining small native frugivores cannot swallow and/or disperse the largest seeds, like those adapted to dispersal by large extinct pigeons in Tonga 3,15,18,21,26,27 . ...
... The only introduced seed disperser, the red-whiskered bulbul, is not known to disperse the largest-fruited or largest-seeded plants, leaving these dependent on a few remaining native frugivores that are threatened with extinction 34,49 . Therefore, the inferred negative impact on plant germination, recruitment success, gene flow, habitat connectivity, source-sink dynamics and local rescue effects [20][21][22][23][24][25][26][27] potentially leaves the native plant community vulnerable to severe declines in abundance and secondary extinctions. Even though we do not show this here directly, there have been several empirical studies linking lower plant recruitment with frugivore extinctions 21,27 , including in the Mascarenes 53 . ...
Insular communities are particularly vulnerable to anthropogenic extinctions and introductions. Changes in composition of island frugivore communities may affect seed dispersal within the native plant community, risking ecological shifts and ultimately co-extinction cascades. Introduced species could potentially mitigate these risks by replacing ecological functions of extinct species, but conclusive evidence is lacking. Here, we investigate changes in plant–frugivore interactions involving frugivorous birds, mammals and reptiles in Mauritius, an oceanic island with an exceptionally well-specified frugivore community and well-described species introduction history. We demonstrate substantial losses of binary interaction partnerships (at the species level) resulting from native species extinctions, but also gains of equal numbers of novel interactions with introduced species, potentially supporting the idea that non-native species might compensate for lost seed dispersal. However, closer investigation of animal seed handling behaviour reveals that most interactions with seed dispersers are replaced by ecologically different interactions with seed predators. Therefore, restoration of seed dispersal functionality in this novel plant–frugivore community is unlikely.
... Rodents also disrupt native plant communities by altering patterns of seed dispersal, but rodents are only part of pervasive changes to island seed dispersal. Avian and other mammalian native seed dispersers have declined to the point of extinction or functional extinction on many Pacific islands (Farwig and Berens 2012;Carpenter et al. 2020;Fernández-Palacios et al. 2021). Identifying how introduced birds and mammals function in the role of seed disperser is crucial to conserve native plant dispersal. ...
Rodents are among the most widespread and problematic invasive animals on islands worldwide contributing to declining endemic island biota through predation and disruption of mutualisms. Identifying what rodents eat is critically important to understanding their effects on ecosystems. We used DNA metabarcoding to identify the diets of three invasive rodents in Hawaiian forests: house mouse (Mus musculus), black rat (Rattus rattus), and Pacific rat (Rattus exulans). These rodents primarily eat invertebrates and plants, but previous diet studies have provided only a limited understanding of the diet breadth by relying on morphological identification methods. We opportunistically collected fecal samples from rodents trapped at seven forest sites across Oʻahu, Hawaiʻi for two years. Plant and invertebrate diet items were identified from DNA extracted from fecal samples using rbcL and COI primers, respectively. Intact seeds were identified using a dissecting microscope to quantify potential contributions to seed dispersal. All rodent species ate primarily plants and invertebrates of introduced species. However, some native taxa of conservation importance were identified. Neither the rodent species nor the sites drove patterns of diet composition, suggesting that diet variation may be determined by opportunistic foraging or intraspecific variation. Black rat fecal samples contained intact seeds more frequently than house mouse samples, but surprisingly, when samples contained seeds, black rats and house mice both defecated hundreds of introduced seeds, likely contributing to seed dispersal. Conservation efforts targeting invasive rodent control should specifically include house mice and should monitor introduced prey items to prevent predation release of unwanted introduced species.
... This population reduction or elimination of frugivorous animals and seed dispersers, such as C. brachyurus, can delay forest regeneration (Farwig & Berens 2012) and induce other negative environmental effects. For example, the disappearance of large animals has caused a reduction in the seed size of some fruit plants that are normally included in the diets of these species (Emer et al. 2020, Del-Claro & Dirzo 2021. ...
Zoochory is a fundamental process that can be the main mechanism for seed and plant dispersal for many species. Mammals of the Carnivora order are among the most important dispersing agents; however, little is known regarding the role of canids as seed dispersers. Although the maned wolf (Chrysocyon brachyurus) has a potentially important role in seed dispersal, given its relatively high consumption of fruits, few studies have investigated the germination rate of ingested seeds. Here, we used seeds removed from the feces of two captive specimens (maned wolf treatment) and those directly collected from unconsumed fruits (control) in germination essays to evaluate the germination rate and emergence velocity index (IVE). We used mature fruits from five species of trees in the Cerrado and Atlantic Forest in a 5 (species) × 2 (method of seed collection) factorial arrangement. The passage of seeds through the digestive tract of the maned wolf favored the germination of Genipa americana and Psidium guajava, delayed germination of Psidium cattleianum, and maintained the germination of Plinia cauliflora and Ficus obtusifolia. Our results revealed that germination occurred for all tested plant species consumed by the maned wolf; therefore, this canid species has high dispersal potential and can be an important ally in the restoration of the Cerrado and Atlantic Forest-Cerrado contact zone ecosystems.
... As some animal species are able to travel long distances with seeds on their outside or seeds inside their guts, zoochory supports the long-distance dispersal of seeds (Nathan, 2006). However, the decline of the seed-dispersing large herbivores severely affecting the dispersal-driven ecosystem processes on a global scale (Burney and Flannery, 2005;Farwig and Berens, 2012;Kamp et al., 2016), and implies that alternative, often overlooked dispersal mechanisms and animal groups plays a key role in seed dispersal interactions (Jansen et al., 2012;Pérez-Méndez and Rodríguez, 2018;Godó et al., 2022). Pérez-Méndez and Rodríguez (2018) stressed that literature about zoochorous seed dispersal was focused for a long time on the role of frugivorous mammals and birds. ...
... Acceleration measurements at animal necks contain valuable information on epizoochorous seed dispersal by wild mammals. Since such measurements are now widely available, there is considerable potential for 'recycling' them [21] to assess the dispersal services provided by wild animals [12]. ...
Background
The seeds of many plant species can be dispersed over long distances in animal fur (epizoochory). Quantifying epizoochory in the wild is, however, challenging, since it is difficult to measure the retention times of seeds in fur. These retention times depend on the acceleration that seeds experience and that can detach seeds from fur. Wildlife collars containing accelerometers may thus provide crucial information on epizoochorous seed dispersal. However, this is only the case if acceleration of the animal’s neck (where collars are attached) is informative of acceleration of the animal’s main body (where most seeds are transported).
Methods
We used accelerometers to simultaneously measure acceleration at the neck, breast and the upper hind leg of 40 individuals of eight mammal species spanning a large range of body masses (26–867 kg). We then quantified maximum acceleration as the 95%-quantile of the resultant acceleration (of all measured values in data intervals of 5 s).
Results
Maximum acceleration was comparable between the neck and breast but substantially higher at the hind leg. Maximum acceleration measured by neck collars and body mass jointly explained 81% of the variance in maximum acceleration of the breast and 62% of the variance in maximum acceleration of the leg.
Conclusions
Acceleration measured by neck collars is informative of the acceleration experienced by seeds attached to other body parts (breast and leg). When combined with animal movement data and lab measurements of how fur acceleration affects seed release and retention times, widely used collar accelerometers can thus be used to assess distances of epizoochorous seed dispersal.
... Even when all mutualistic dispersers are lost simultaneously, plants may still persist, if seed dispersal by gravity, wind or water is sufficient 42,43 . Understanding the long-term consequences of seed dispersal is required to gain insights into the coevolution of plants and animal mutualists [44][45][46] , and should be used to improve conservation management decisions 47,48 . ...
Mutualistic interactions are by definition beneficial for each contributing partner. However, it is insufficiently understood how mutualistic interactions influence partners throughout their lives. Here, we used animal species-explicit, microhabitat-structured integral projection models to quantify the effect of seed dispersal by 20 animal species on the full life cycle of the tree Frangula alnus in Białowieża Forest, Eastern Poland. Our analysis showed that animal seed dispersal increased population growth by 2.5%. The effectiveness of animals as seed dispersers was strongly related to the interaction frequency but not the quality of seed dispersal. Consequently, the projected population decline due to simulated species extinction was driven by the loss of common rather than rare mutualist species. Our results support the notion that frequently interacting mutualists contribute most to the persistence of the populations of their partners, underscoring the role of common species for ecosystem functioning and nature conservation.
... Cerca del 35% de las poblaciones de primates ocupan las categorías de Vulnerable, Amenazado y Críticamente Amenazado (IUCN 2007;2014). Por lo tanto, la extinción o reducción drástica de las poblaciones de vertebradores dispersores grandes y su rol de la dispersión de semillas podría eventualmente producir cambios en la dinámica de regeneración en los bosques neotropicales (Beck et al., 2013;Brocardo et al., 2013;Kurten, 2013), y los efectos podrían desencadenar cambios al nivel de la comunidad y funcionamiento de estos ecosistemas en el largo plazo (Farwig & Berens, 2012). ...
Los vertebrados frugívoros en los bosques amazónicos enfrentan fuertes presiones de caza en el presente, y su disminución o desaparición pueden desencadenar grandes cambios dentro del ecosistema. Presentamos los resultados de un estudio de la dispersión de semillas de especies forestales consumidas por frugívoros arbóreos en tres localidades de bosques inundables en la cuenca de Río Madre de Dios (Tambopata Research Center, Estación Biológica Los Amigos y Reserva Amazónica), que representan un gradiente de perturbación y densidad de vertebrados frugívoros. En cada sitio, se seleccionó un área de ~1 hectárea (104m x 104m) en donde se instalaron 196 trampas de semillas, distribuidas uniformemente por una gradilla de 14 columnas y filas. Cada 15 días durante un periodo de 135 meses, se colectó, identificó y registró semillas de las especies forestales con frutos carnosos encontradas en las trampas. Presentamos los datos analizados de 10 especies forestales (7 familias) dispersadas principalmente por primates, aves y/o murciélagos frugívoros. Los resultados muestran que la reducción de densidad de los vertebrados frugívoros grandes afecta la dispersión de semillas de especies forestales que dependen principalmente por estas especies, mientras otras especies forestales que no dependen de dispersores cazados son menos afectadas. Se necesita realizar más estudios a largo plazo que permitan una evaluación más rigurosa de las consecuencias de la desaparición de grandes vertebrados frugívoros arbóreos sobre la ecología de regeneración en los bosques de la región de Madre de Dios.
... Seed dispersal through frugivory provides food to animals and contributes to the maintenance of plant populations, hence being an important ecosystem service (Farwig and Berens 2012). Seed dispersal by fish (ichthyochory) is an important interaction, as freshwater fishes can consume fruits from about 600 Neotropical plant species (Correa and others 2015a). ...
Frugivory and seed dispersal by fish is an important mutualistic interaction in complex and species-rich tropical rivers. The local ecological knowledge (LEK) held by fishers can provide new information on relationships between fishes and plants in less studied rivers. This study aims to investigate the feeding interactions between frugivorous fish and plants through interaction networks based on the fishers' LEK in three rivers in the Brazilian Amazon (Negro, Tapajó s and Tocantins). A total of 418 fishers were interviewed in 24 communities (eight in each river). The studied fishes were tambaqui (Colossoma macropomum), matrinxã (Brycon spp.), pacu (Myloplus spp.), pacu manteiga (Mylossoma duriventre), pirapitinga (Piaractus brachypomus), and jaraqui (Semaprochilodus spp.). The interviewed fishers cited a total of 92 plants consumed by the six frugivorous fishes in the three rivers. The interaction networks showed a higher nestedness in the Tocantins, greater connectance and modu-larity in the Tapajó s and more specialization in the Negro, where the protected areas may have contributed to a more complex and specialized interaction network. The more nested network in the Tocantins River indicated the loss of specialized interactions in disturbed communities. The Tapajó s River network showed the highest number of interactions between fish and plants, but this river has been threatened by environmental changes. Fishers' LEK associated to network analyses can advance our understanding on ecological interactions. This approach can be also useful to evaluate and mitigate ecological effects from anthropic changes in the Amazon and other high diverse tropical rivers.
... These introductions have directly and indirectly altered mutualistic interactions, such as pollination and seed dispersal [3,4]. Mutualistic interactions between plants and animals are key for ecosystem functioning, since most plant species depend on biotic vectors for reproduction and recruitment [5], with 90% of plants dispersed by animals in tropical regions and 60% in temperate regions [6]. In addition, seed dispersal maintains gene flow among populations and facilitates recruitment and seedling establishment [7]. ...
Exotic species are one of the main threats to biodiversity, leading to alterations in the structure and functioning of natural ecosystems. However, they can sometimes also provide ecological services, such as seed dispersal. Therefore, we assessed the ecological impacts of exotic species on native dispersal systems and the mechanisms underlying the disruption of mutualistic plant-disperser interactions. Exotic species negatively affect dispersal mutualisms by (i) altering dispersal behavior and visitation rates of native dispersers, (ii) predating native dispersers, (iii) transmitting forest pathogens, and (iv) predating seeds. Conversely, positive impacts include the dispersal of native plants, forest regeneration, and native habitat restoration via (i) increasing the visitation rates of frugivorous birds, (ii) facilitating the colonization and establishment of native forest trees, (iii) enhancing forest species seedling survival, and (iv) facilitating seed rain and seedling recruitment of early and late successional native plants. The reviewed studies provide similar results in some cases and opposite results in others, even within the same taxa. In almost all cases, exotic species cause negative impacts, although sometimes they are necessary to ensure native spe-cies' persistence. Therefore, exotic species management requires a comprehensive understanding of their ecological roles, since the resulting effects rely on the complexity of native-exotic species interactions.
... It helps plants establish in new sites and influences the composition of the future vegetation community (Howe & Miriti, 2004;Razafindratsima & Dunham, 2016;Schupp & Fuentes, 1995). Thus, it can facilitate the natural regeneration of degraded landscapes (Chazdon & Guariguata, 2016), consequently reducing management costs associated with active reforestation projects (Farwig & Berens, 2012). While some regenerating forests may benefit from seeds that are already within the soil (seed bank), in most cases, succession depends on the arrival of seeds from mature forests that are often dispersed by frugivores (Alvarez-Buylla & Martínez- Ramos, 1990;Duncan & Chapman, 1999;Guariguata & Ostertag, 2001). ...
Habitat loss is the greatest threat to primate survival. However, land altered for logging or agricultural developments is often abandoned and can regenerate after use. These regenerating forests are critical for the future of primate conservation as they provide habitats and connectivity between mature forest fragments. They can also contribute to climate change mitigation. In this chapter, we introduce what constitutes a regenerating forest, how widespread they are, and how secondary succession varies depending on disturbance history and ecological characteristics. We also examine the role primate seed-dispersal plays in forest regeneration: from the transportation of seeds to changes that occur within a primate’s gut that facilitate germination and impacts on plant communities. We consider how primates might cope with living in a regenerating forest, in terms of behavioral plasticity, from changes in diet to ranging patterns or group cohesion. We argue that the study of primates in regenerating forests is currently lacking and will be pivotal for future primate conservation planning.
... In fact, both endozoochorous and anemochorous dispersal are negatively related with naturalization incidence. Considering endozoochorous traits, non-native plants can easily integrate into native dispersal networks because frugivorous vertebrates are often highly generalist (Farwig and Berens 2012, Heleno et al. 2013, Traveset and Richardson 2014. One possibility is that nonnative plants may show limited naturalization because there is great competition with native plants for the available animal dispersers (Debussche and Isenmann 1990). ...
Understanding what drives non-native species naturalization (the establishment of a self-sustainable population outside its native range) is a central question in invasion science. Plant capacity for long-distance dispersal (LDD) is likely to influence the spread and naturalization of non-native species differently according to their introduction pathways. These pathways include intentional introductions (for economic use, e.g. for agriculture), unintentional introductions (e.g. seed contaminants), plant dispersal via human infrastructures (e.g. roads) and plant spread from an adjacent region where the species was previously introduced. We tested the relationship between sets of LDD traits (syndromes) of 10 308 European plant species and their global naturalization incidence (i.e. whether a species has become naturalized or not) and extent (i.e. the number of regions where a species has become naturalized) using the most comprehensive database of naturalized plants worldwide (GloNAF). Diaspore traits allowed the identification of four traditional LDD syndromes, namely those with specializations for dispersal by: wind (anemochorous), animal ingestion (endozoochorous), attached to animals (epizoochorous) and sea currents (thalassochorous). These evolutionary spe-cializations have been historically interpreted by biologists even though actual dispersal is not always related to diaspore syndromes. We found that while epizoochorous and thalassochorous traits are positively associated with global plant naturalization incidence , anemochorous and endozoochorous traits show a negative relationship. Species' residence time outside their native range, their economic use and presence of epizo-ochorous traits (such as hooks, hairs and adhesive substances) are positively associated with global naturalization extent. Furthermore, we found that plant economic use reduces the influence of LDD syndromes on the naturalization incidence of intentionally introduced plants. While the success of non-native plants is influenced by a broad array of species-and context-specific factors, LDD syndromes play an important role in this context depending on the economic use of plants.
... Most behavioral work has examined how smoke (and burning more generally) may attract or repel insects, with some biochemical work on response mechanisms. As insects have different functional roles within ecosystems, such as plant pollinators (Ollerton 2017) and seed dispersers (Farwig and Berens 2012), one potential research area is the impact of LFS on insect ecosystem services. Sagili and Chakrabarti (2021) suggested that smoke pollution from wildfires decreased the pollination services of honey bees, providing rare evidence showing that LFS impacts insect ecological function. ...
Landscape fire activity is changing in many regions because of climate change. Smoke emissions from landscape fires contain many harmful air pollutants, and beyond the potential hazard posed to human health, these also have ecological impacts. Insects play essential roles in most ecosystems worldwide, and some work suggests they may also be sensitive to smoke exposure. There is therefore a need for a comprehensive review of smoke impacts on insects. We systematically reviewed the scientific literature from 1930 to 2022 to synthesize the current state of knowledge of the impacts of smoke exposure from landscape fires on the development, behavior, and mortality of insects. We found: (1) 42 relevant studies that met our criteria, with 29% focused on the United States of America and 19% on Canada; (2) of these, 40 insect species were discussed, all of which were sensitive to smoke pollution; (3) most of the existing research focuses on how insect behavior responds to landscape fire smoke (LFS); (4) species react differently to smoke exposure, with for example some species being attracted to the smoke (e.g., some beetles) while others are repelled (e.g., some bees). This review consolidates the current state of knowledge on how smoke impacts insects and highlights areas that may need further investigation. This is particularly relevant since smoke impacts on insect communities will likely worsen in some areas due to increasing levels of biomass burning resulting from the joint pressures of climate change, land use change, and more intense land management involving fire.
... For example, it is likely that decreasing faunal movement between habitat fragments reduces the effective dispersal distance for many plant species, particularly those with large seeds dependent on animal vectors (McConkey et al., 2012). Reduced dispersal distances have severe consequences for all species susceptible to inbreeding, genetic drift, and may also hinder recolonising patches after local extinctions (Farwig & Berens, 2012). Any species loss, particularly of digging Critical Weight Range (CWR) mammals (i.e. ...
Consumption of seeds by fruit-eating animals is one of the most effective dispersal mechanisms for plants, yet little is known about dispersal by marsupial vectors. In the face of habitat fragmentation and the recent extinction or decline of many marsupial species in southern Australia, addressing knowledge gaps on vertebrate vectors is critical to determine deficiencies in seed dispersal. Here we examine one potential dispersal vector for the seeds of Cassytha pubescens, a native hemi-parasitic vine that contributes to vegetation complexity within many woodland habitats in southern Australia that are threatened by fragmentation. To determine the potential dispersal role of mammals for Cassytha pubescens within southern Australian woodlands, we collected and examined 46 scat samples from the omnivorous, nationally endangered southern brown bandicoot, Isoodon obesulus, over two fruiting (summer) seasons. Of the 46 scats, five had up to six seemingly undigested seeds of C. pubescens, indicating that I. obesulus consumes the fruits and may act as a disperser for this vine. Our findings improve understanding of the role of marsupials like bandicoots in dispersing native plant seed and may help to inform conservation management priorities to protect ecosystem function more effectively in fragmented woodlands threatened by loss of vertebrate seed vectors.
... The global decline of the seed-dispersing large herbivores threatens the dispersal-driven ecosystem processes worldwide (Farwig and Berens, 2012;Ripple et al., 2015), and implies that the relative importance of other dispersal vectors might increase (Burney and Flannery, 2005;Wotton and Kelly, 2011). A severe decline of large herbivores occurred recently in the Palaearctic steppes where due to poaching the populations of wild grazers have decreased remarkably, whereas the area grazed by livestock has been retreated to the vicinity of settlements, leaving vast steppe areas without any large herbivores (Kamp et al., 2016). ...
Zoochory is an ecologically and evolutionarily important seed dispersal type. The decline and extinction of seed-dispersing large herbivores severely threatens dispersal-driven ecosystem processes in many regions. Hence the relative importance of small rodents and lagomorphs (Glires, Mammalia) as dispersal vectors might increase due to their ubiquity, diversity and abundance. Here we provide a review of rodent- and lagomorph-mediated seed dispersal based on approximately 600 papers found in an extensive literature search. We highlight that small rodents and lagomorphs disperse seeds via various mechanisms. The seldom documented epi- and endozoochory are probably universal in these groups. Due to their small home range, short fur and small body size, these mechanisms generally operate at small scales and mainly for small seeds. Taxon-specific feeding, nesting and behavioural characteristics provide a wide spectrum of other seed dispersal types, such as synzoochory (food caching). The studied taxa generally support seed dispersal within a particular habitat patch, contributing to the persistence of local populations, but in rare cases, long-distance dispersal events might occur. Besides seed dispersal, rodents and lagomorphs can also support plant establishment and provide safe sites for seeds where they can survive stochastic events. Studies reviewed here show a strong bias both in scope and geographical distribution: synzoochorous dispersal of woody plants is known in detail, and most studies were conducted in the same few countries and habitat types. In contrast, other mechanisms such as endozoochory, epizoochory and habitat types like grasslands and anthropogenic habitats have rarely been studied. We show examples on ecosystem services and disservices related to rodent- and lagomorph-mediated seed dispersal as well as the importance of these processes in habitat conservation and restoration.
... Seed dispersal is an important process for plant reproductive success, playing a key role in the functioning and dynamics of communities (Traveset and Richardson, 2006;Corlett, 2017) as well as in maintaining biodiversity (Bascompte and Jordano, 2007;Valiente-Banuet et al., 2015). This mutualistic interaction benefits both parties, by providing food resources for animals, and promoting the colonization of new ranges and escaping from competing siblings for plants (Farwig and Berens, 2012). Plants are highly dependent on animals for seed dispersal in different biomes, with 90% of trees being dispersed by animals in tropical regions (Howe and Smallwood, 1982) and up to 60% in temperate regions (Willson et al., 1990). ...
Seed dispersal is a critical process for plant reproduction and regeneration. Successful recruitment depends on pre-and post-dispersal processes that complete a seed's journey until becoming a new plant. However, anthropogenic stressors may disrupt the seed dispersal process at some stages, collapsing plant regeneration and hampering its long-term persistence. The Chilean palm tree Jubaea chilensis is the southernmost and the only non-tropical palm species, which currently relies on the scatter-hoarding rodent Octodon degus for seed dispersal. We assessed seed fate by measuring predation and dispersal rates through experimental fieldwork in the Palmar de Ocoa site (located within La Campana National Park) and the Palmar El Salto. We also used previous reports on seed harvest and seedling herbivory to depict the whole J. chilensis seed dispersal process and assess the relative importance of different anthropogenic pressures. We asked the following questions: (1) What is the effect of human harvesting on J. chilensis recruitment? (2) Do native and exotic rodents predate J. chilensis seeds in the same way? and (3) Does post-dispersal herbivory matter? We found that J. chilensis fruits are harvested for human consumption, reducing pre-dispersal available seeds by removing about 23 tons per season. Then, post-dispersal seeds at the Ocoa palm grove are heavily predated by exotic (Rattus rattus) and native (Octodon spp.) rodents; only 8.7% of the seeds are effectively dispersed by Octodon degus. At Palmar El Salto, 100% of the seeds were predated by Rattus rattus, precluding further analysis. Finally, 70% of the seedlings were consumed by exotic herbivores (mainly rabbits), resulting in a success rate of 1.81%. Only 7.9% of the surviving seedlings become infantile plants (4 year-old). Our assessment suggests that J. chilensis has aging populations with very few young individuals in disturbed sites to replace the old ones. For those reasons, we suggest increasing its conservation category to critically endangered as land-use change is rapidly fragmenting and shrinking the extant J. chilensis populations. We urge to take urgent actions to protect this relict palm, which otherwise may go extinct in the next decades.
... Over time, reductions in frugivorous birds due to SWD may lead to shifts in plant communities away from fruit-producing species (Matlack 1994). Changes to the plant community may lead to changes in carbon storage, nutrient cycling, and natural restoration capacity (Lovett et al. 2016), and ultimately to declines in ecosystem function (Farwig and Berens 2012) and resilience (Table 1; Gunderson 2000, Folke et al. 2004). ...
Invasion of forest ecosystems by non‐native invasive insect pests (NNIIPs) can alter native animal and plant communities by disrupting species interactions. However, little is known about how fruit‐targeting NNIIPs may alter forest ecosystems. Recently introduced to the western United States, spotted wing Drosophila ( Drosophila suzukii ; SWD) is a parasite of soft‐skinned fruits. The ability of SWD to parasitize still‐ripening fruits of many plant species led to rapid expansion in agricultural systems across North America. Recent surveys have documented widespread SWD parasitism of wild fruits in forests, although impacts of parasitism remain unexplored. We investigated how SWD may produce ecological changes to eastern forests through several mechanisms: 1) disruption of plant–animal seed dispersal interactions; 2) subsequent alterations to plant community composition; and 3) changes in fruit consumption by wildlife. Parasitism of fruits by SWD may reduce attractiveness to potential seed dispersers, reducing overall consumption and shifting future plant communities away from fruit‐producing species. Invasion by SWD may therefore have both short‐term and long‐term consequences for food resources for wildlife and ecosystem function. We highlighted frugivorous birds because of their importance as consumers and dispersers of fruits in eastern North America and their well‐documented rejection of parasitized fruits. We proposed several critical avenues of research and call for a large‐scale collaborative effort to understand the complex relationship SWD may play with plants and wildlife in forest ecosystems. © 2021 The Wildlife Society.
... Both, bats and birds are ecologically diverse groups and include seed dispersers, pollinators, and arthropod predators Whelan et al., 2008). The high mobility of flying vertebrates is also key to provide genetic connectivity among plants within and among ecosystems across large spatial scales, e.g., through seed dispersal and pollination (Boyles et al., 2011;Farwig & Berens, 2012). Hence, flying vertebrates contribute to the persistence of plant species and ecosystem functioning, directly affect forest integrity and regeneration (Wandrag et al., 2017), and also deliver essential ecosystem services to humans Whelan et al., 2008). ...
Given the current challenges of global change, e.g., through increasing temperatures and changes in habitat quality, it is essential to gain a better understanding of how species are linked to the conditions of their environment. Bats and birds fulfill crucial ecosystem functions as highly mobile long-distance seed dispersers, pollinators, and insect predators and might be influenced not only by abiotic conditions such as temperature, but also by structural parameters of their habitats. We hypothesized that mean annual temperature and vegetation structures are key determinants of flying vertebrate species richness along the slopes of Mt. Kilimanjaro, Tanzania. We used Light Detection and Ranging (LiDAR) to characterize the three-dimensional habitat structure across different forest strata and recorded mean annual temperature on 58 study sites along the elevational gradient of Mt. Kilimanjaro. Our results show that both bat and bird species richness were significantly associated with temperature and a LiDAR derived measure of canopy density. In combination, temperature and LiDAR-derived vegetation structure described over 90% of the variability in bat and bird species richness along the elevational gradient. Our findings reveal that climate data and measures of canopy structure obtained by remote sensing can be used to approximate the richness of flying vertebrates on tropical mountains and are highly suitable monitoring tools in conservation programs for these functionally important taxa.
... There is ample evidence that disperser loss affects plant populations (reviewed in Beckman & Rogers 2013, Farwig & Berens 2012, Howe & Miriti 2004, Kurten 2013, McConkey et al. 2012. Studies assessing impacts of disperser loss on plant regeneration have shown a decrease in seed germination (Cochrane 2003, Pérez-Méndez et al. 2018) and limitations in recruitment (Cordeiro & Howe 2003, Traveset et al. 2012, Wotton & Kelly 2011, Wright & Duber 2001. ...
Seed dispersal is key to the persistence and spread of plant populations. Because the majority of plant species rely on animals to disperse their seeds, global change drivers that directly affect animals can cause cascading impacts on plant communities. In this review, we synthesize studies assessing how disperser loss alters plant populations, community patterns, multitrophic interactions, and ecosystem functioning. We argue that the magnitude of risk to plants from disperser loss is shaped by the combination of a plant species’ inherent dependence on seed dispersers and the severity of the hazards faced by their dispersers. Because the factors determining a plant species’ risk of decline due to disperser loss can be related to traits of the plants and dispersers, our framework enables a trait-based understanding of change in plant community composition and ecosystem functioning. We discuss how interactions among plants, among dispersers, and across other trophic levels also mediate plant community responses, and we identify areas for future research to understand and mitigate the consequences of disperser loss on plants globally.
Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 52 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... Since then, the focus of biological conservation has expanded from protecting flagship species and areas to including the integrity of ecosystem functioning and interactions between species (Grumbine, 1994;Pikitch et al., 2004;Jordano et al., 2006). Such interactions between plants, animals, or both play a critical role in the maintenance of ecological communities (Jordano et al., 2006;Farwig & Berens, 2012). Further than their intrinsic conservation value, these ecological interactions also provide ecosystem services, which are essential to human life and wellbeing (Constanza et al., 1997;Kubiszewski et al., 2017). ...
• Frugivorous fish provide often conflicting ecosystem services of seed dispersal and food provisioning in tropical rivers. Fishing may reduce the size and abundance of frugivorous fish, thus affecting their potential as seed dispersers, which could affect the conservation of these fish and of floodplain forests.
• The goal of this study was to assess the influence of co-managed protected areas in the form of extractive reserves (RESEX) and small-scale fisheries on frugivorous fish in the Tapajós and Negro rivers, in the Brazilian Amazon. The study examined whether: (i) frugivorous fish are important for fisheries and selectively caught; and (ii) frugivorous fish abundance, size and fisheries catch per unit of effort are higher inside the RESEX than outside.
• The analyses included fisheries-dependent data (3,753 fish landings) and independent data (12,730 sampled fish) collected in 16 fishing communities (eight for each river). In both rivers, frugivorous fish are among the 10 species caught the most and frugivorous biomass was proportionately higher in landings than in samplings, indicating fisheries selectivity towards these fishes.
• In both rivers, catches of frugivorous fish were higher outside the RESEX than inside. Catch per unit effort and the proportion of frugivores in the catch were higher outside the RESEX in the Tapajós River but did not vary between sites inside and outside the RESEX in the Negro River. Frugivorous fish were larger inside the RESEX in the Negro, but smaller inside the RESEX in the Tapajós.
• The results indicated that the ecosystem services of seed dispersal and food source provided by frugivorous fish are not in conflict in the tropical rivers studied. Therefore, these clearwater and blackwater rivers in the Brazilian Amazon show a balance between fisheries and conservation of frugivorous fish, which play an essential role in the functioning of tropical floodplain forest ecosystems.
... Mammal-seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide (Farwig & Berens 2012). The consumption of seeds by mammals may result in either predation (when the seed is destroyed) or dispersal (when the seed remains viable) and, consequently, can be either detrimental or beneficial for plants (Torres, Castaño & Carranza-Quiceno 2020). ...
Mammal-seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide. Many Australian mammals consume seeds, but their role in seed dispersal has not been well explored. The translocation of Australian mammals for the purposes of ecosystem restoration is increasing. Digging mammals,
i.e. species that dig to obtain food or create shelter, are commonly the focus of these translocations because they are ecosystem engineers but an understanding of their role in seed dispersal is lacking. We aimed to expand the understanding of endozoochory in Australian digging mammals by determining whether seeds consumed by select species remain viable and able to germinate. Firstly, we investigated the mean retention time and the postconsumption germination capacity of Australian seeds (Acacia acuminata, Dodonaea viscosa and Gastrolobium calycinum) likely to be consumed by quenda (Isoodon fusciventer) and woylies (Bettongia penicillata ogilbyi) while in captivity. Secondly, we collected scat samples from five wild digging mammal species (boodie, B. lesueur; woylie, B. penicillata; bilby, Macrotis lagotis; golden bandicoot, I. auratus and quenda, I. fusciventer) known to consume seeds across nine sites in Western and South Australia. We searched the scat samples for seeds, identified the recovered
seeds and then tested their viability and germination capacity. Mean excretion times in captive individuals were 14 hours for quenda and 24 hours for woylies, but some seeds were retained in their digestive passages for up to 39.5 and 55.5 hours, respectively. In captive settings, viable seeds of all plant species were retrieved from both quenda and woylie scats and only G. calycinum seeds ingested by quenda (62%) had a significantly higher germination percentage than control seeds (34%). In wild animals, we found that the abundance of intact seeds in scats was generally low but 70% of the retrieved seeds appeared viable. Five species of seed collected from scats of wild digging mammals germinated under laboratory conditions. Our results show that viable seeds are deposited in the scats of Australian digging mammals, indicating that these species may play a more important role in seed dispersal than previously considered. Digging mammals have the potential to contribute to ecosystem restoration efforts through the dispersal of viable seeds but there is also a risk that non-native species could be dispersed. These costs and
benefits should be considered by practitioners when planning reintroductions of digging mammals.
... Such mechanisms can effectively disperse seeds over large distances from the parent plant and increase germination chances (Vittoz & Engler, 2007). When alien plants interact with animal-mediated dispersal of native plants, it will disrupt native mutualisms that evolved over evolutionary time (Farwig & Berens, 2012;Traveset & Richardson, 2014). Hence, an understanding of invasive plants' dispersal mechanisms and identifying the native seed dispersers are important for their future management (Richardson et al., 2000). ...
Senna spectabilis, a native tree of tropical America is rapidly colonizing the forests of Western Ghats. We identified the Asian elephant (Elephas maximus) as the major disperser of Senna, with the dung facilitating germination of the species. The study provides critical information for the management of Senna in tropical Asia. Senna spectabilis (DC.) Irwin & Barneby, a native tree of tropical America, is rapidly invading different forest types globally especially in the Western Ghats biodiversity hotspot, posing severe threats to its biodiversity. The Wayanad Wildlife Sanctuary in the Western Ghats is one of the heavily infested areas by S. spectabilis. Here, we identified the native seed dispersers of S. spectabilis by analyzing the feces of native mammals in the sanctuary. We found that three mammal species were found dispersing their seeds viz. Asian elephant (Elephas maximus), Chital (Axis axis), and Indian crested porcupine (Hystrixindica). Among the animals, elephants dispersed a large number of seeds. These findings have direct and long‐lasting implications for the ongoing efforts to reduce this highly invasive plant species’ spread and management in the Western Ghats.
... During the invasion process and the integration into a native community, an exotic plant may indirectly affect the interactions among native species. The most common effect observed is the disruption of the mutualism between native partners (Traveset and Richardson 2006, Farwig and Berens 2012, Heleno et al. 2013a, arguably driven by invasive fruits being more abundant or nutritious than native fruits (Kueffer et al. 2009, Mokotjomela et al. 2013a. Consequently, fruit removal of the native plants declines, reducing their dispersal success (Mokotjomela et al. 2013b). ...
Biological invasions are one of the main threats to biodiversity and ecosystem functioning in the Anthropocene. Fleshy-fruited invasive plants establish mutualistic interactions with native seed dispersers and may affect the mutualisms between native partners, negatively by disrupting plant dispersal through competition for seed dispersers or positively by facilitating seed dispersal via the attraction of fruit-eating animals. Moreover, the invaders' density in the neighborhood of native plants may modulate the direction and/or magnitude of such effects on natives. In mountains of central Argentina, the cessation of fruiting of the dominant native tree Lithraea molleoides overlaps with the beginning of the fruiting of invasive shrubs (Pyracantha spp.). This partial overlap allows for testing opposite predictions regarding the effect of invasive fruits on native seed dispersal. We compared frugivory by seed disperser birds on L. molleoides during non-overlapping and overlapping periods, at six sites that differed in Pyracantha shrub density (high, low and no-invasion). We counted frugivory during 2 h on 15 individuals of L. molleoides at each site and period, totaling 360 h of observation. Frugivory on the native tree was similar among sites during the non-overlapping period and remained constant in both periods at non-invaded sites. At invaded sites, frugivory increased from non-overlapping to overlapping period and was greater at highly invaded sites. The resource provided by Pyracantha did not disrupt seed dispersal of the dominant native tree. Rather, it facilitated frugivory by seed dispersers and this effect may be exacerbated with higher fruit availability of invasives. Our results provide a counterview to the prevailingly negative impacts of invasive species on the seed dispersal of native species since the fruiting of invasive plants facilitated the seed dispersal of native species in a continental region contrasts with the mutualism disruption commonly observed in insular environments.
... Mammal-seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide (Farwig and Berens 2012). The consumption of seeds by mammals may result in either predation (when the seed is destroyed) or dispersal (when the seed remains viable) and, consequently, can be either detrimental or beneficial for plants (Torres et al. 2020). ...
Context. Mammal–seed interactions are important for structuring vegetation communities across a diverse range of
ecosystems worldwide. In Australia, mammals are typically considered to be seed predators and to play insignificant roles
in seed dispersal. However, very few studies have investigated endozoochorous seed dispersal in Australian species. The
translocation of Australian mammals for the purposes of ecosystem restoration is increasing. Digging mammals (i.e.
species that dig to obtain food or create shelter) are commonly the focus of these translocations because they are considered
to be ecosystem engineers, but an understanding of their role in seed dispersal is lacking.
Aims. The aim of the present study was to expand the understanding of endozoochory in Australian digging mammals
by determining whether seeds consumed by select species remain viable and able to germinate.
Methods. Scat samples were collected from five digging mammal species, known to consume seeds or fruit, across nine
sites in Western and South Australia. The samples were searched for seeds, with the recovered seeds identified and tested
for viability and germination capacity.
Key results. The abundance of intact seeds in scats was generally low, but 70% of the retrieved seeds appeared viable.
Five species of seed germinated under laboratory conditions. These seeds were retrieved from bilby (Macrotis lagotis),
boodie (Bettongia lesueur), golden bandicoot (Isoodon auratus) and quenda (I. fusciventer) scats.
Conclusions. Seeds consumed by Australian digging mammals can remain viable and germinate, indicating that
digging mammals play a more important role in seed dispersal than previously considered.
Implications. Digging mammals have the potential to contribute to ecosystem restoration efforts through the dispersal
of viable seeds, but there is also a risk that non-native species could be dispersed. These costs and benefits should be
considered by practitioners when planning reintroductions of digging mammals.
... The consequences of animal loss on seed dispersal might be species specific in sympatric plants because of the different seed preferences of animals Zhang et al., 2016). Furthermore, plants dispersed by specialists are more likely to be constrained by dispersers' loss than those dispersed by generalists because functional loss of dispersal service in generalists dispersed plants may be partially compensated for by multiple dispersers (Galetti et al., 2006;Jorge and Howe, 2009;Farwig and Berens, 2012). A large body of works has studied the effects of animal loss on seed dispersal and seedling regeneration in many plant species in fragmented forests, but fewer of them have compared the different consequences induced by animal loss between sympatric plants from seed to seedlings (e.g., Howe, 2001, 2003;Valdivia and Simonetti, 2007;Jorge and Howe, 2009;Lai et al., 2014;Zucaratto and Pires, 2015;Zeng et al., 2019). ...
The local extinction or reduction of a species or even a small functional group as a result of forest fragmentation may have different consequences on the sympatric plants. Here, we investigated acorn dispersal and seedling recruitment, along with the mortality of two oak species, Quercus variabilis with large acorn and Quercus chenii with small acorn, in an isolated forest patch in Wuhan city, central China, where rodents are rare, but birds (e.g., Eurasian jay) are present. We hypothesized that a reduction of rodents would induce greater threats to the regeneration of oaks with large acorn than that with small acorns because bird dispersers may prefer to disperse small acorns. The results showed that, for both of the oak species, very few acorns were dispersed on the ground surface, leading to a cluster distribution of newborn seedlings underneath adults, which was followed by a high mortality in the next year. However, due to the existing Eurasian jay preferring to harvest small acorns, more small Q. chenii acorns were dispersed than large Q. variabilis acorns, resulting in fewer distributions of clusters and a lower mortality of Q. chenii seedlings than Q. variabilis in the experimental patch. These results suggest that the loss of granivorous rodents in urban forests may result in low regeneration of rodent-dispersed species, but this degradation of ecological function can be partially buffered by bird dispersers (e.g., Eurasian jay) for small-seeded trees. Ecological-based management of rodents and birds are needed in urban forests to ensure their sustainability.
... Seed dispersal is altered at forest edges via multiple mechanisms (Traveset and Richardson 2006). Previous studies have found that high-quality seed disperser(s) are lower or absent in edge habitats due to suboptimal conditions, a lack of recruitment to edges, or changes in foraging behavior (Ness and Morin 2008, Farwig and Berens 2012, Albrecht et al. 2013, Leal et al. 2014, Warren et al. 2015b. Edge conditions also increase the abundance or diversity of poor-or low-quality seed-dispersing species that interact with seeds, but fail to disperse seeds effectively (Ness 2004, Albrecht et al. 2013, or antagonistic species that damage or consume seeds (Kollmann and Buschor 2003, Ness and Morin 2008, Chen et al. 2017. ...
Seed dispersal by ants is an important interaction in North American eastern deciduous forests, where 30–40% of understory plants are myrmecochores, with seeds that possess lipid-rich appendages (elaiosomes) that attract seed-dispersing ants. Contemporary forests are fragmented and have regenerated from being previously cleared (secondary forests). In secondary forests, and especially along edges, myrmecochores are a depauperate component of forests. Here, we assess if seed dispersal of myrmecochores by ants, particularly the keystone disperser, Aphaenogaster sp., is intact in forest interiors compared to edges. In three North American northeastern deciduous forests, we compared myrmecochore cover and richness, seed dispersal by ants, and the abundance and richness of ants and other forest floor invertebrates between interiors and edges. We also conducted a seed removal experiment, excluding either ants, rodents (seed predators), or ants and rodents, to test their effects on seed dispersal between interiors and edges.We found differences in the composition of understory plants between interiors and edges, with edges lacking myrmecochores. We also found that seed dispersal by ants was lower in two of the three edges and corresponded to Aphaenogaster sp. abundance. Antagonistic interactions with an invasive slug that is an elaiosome robber, Arion subfuscus, was more apparent than damage by rodents in the experiment, negatively affected dispersal by ants more at edges than in interiors. Here we show that changes in mutualistic and antagonistic interactions affect seed dispersal at forest edges and that not all forest edges are the same, with some more intact than others. Understanding how seed dispersal is impacted in contemporary forests is important towards the goal of conserving and restoring depauperate forest understory communities.
... Nearly 95% of the world's plant species belong to families that are characteristically mycorrhizal (Pringle et al., 2009). More than 90% of flowering plants are pollinated by animals (Ollerton et al., 2011), and many plants produce seeds that rely on dispersal by animals to sustain populations and to colonize new habitats (up to 90% of plant species in the tropics require animals for dispersal; Farwig and Berens, 2012). Many plant-plant interactions are also mediated by interactions with other organisms, notably herbivores and pathogens (see below). ...
This book contains 23 chapters divided into seven parts. Part I reviews the key hypotheses in invasion ecology that invoke biotic interactions to explain aspects of plant invasion dynamics; and reviews models, theories and hypotheses on how invasion performance and impact of introduced species in recipient ecosystems can be conjectured according to biotic interactions between native and non-native species. Part II deals with positive and negative interactions in the soil. Part III discusses mutualistic interactions that promote plant invasions. Part IV describes antagonistic interactions that hinder plant invasions, while part V presents the consequences of plant invasions for biotic interactions among native species. In part VI, novel techniques and experimental approaches in the study of plant invasions are shown. In the last part, biotic interactions and the management of ecosystems invaded by non-native plants are discussed.
... Or, alternatively, in areas with high levels of seed predation and/or herbivory where dispersed propagules are unlikely to become established (McAlpine et al., 2016). Thus, this long-term study reinforces the notion that forest managers should consider both the environmental conditions determining tree recruitment as well as the biological processes that amplify plant fertilization and recruitment dynamics, such as seed dispersal or effective pollination (Farwig & Berens, 2012;Potts et al., 2016). ...
... This might have more consequences in young naturally regenerated habitats, which were structurally and compositionally simplified due to the high coverage of ferns and a paucity of remnant trees, leading to reduced ecological niche space within these habitats. Although tree cover and fruiting were much more restored in assisted regenerated sites, the fact that restoration was done in patches of typically around 500 m 2 may deter frugivores whose reliance on a continuous forest cover has been noted (Farwig and Berens, 2012;Farwig et al., 2017). The high density of young trees within restored patches and little herbaceous understorey may also reduce the permeability of these patches to invertivore birds with gap preferences such as Caprimulgus poliocephalus and Bathmocercus rufus (Vande weghe and Vande weghe, 2011). ...
The necessity to restore rainforest habitats degraded by anthropogenic fires is widely recognized, however, research on restoration approaches has mainly centred on the recovery of forest structural complexity. There is insufficient evidence on the efficacy of restoration methods in the recovery of the faunal diversity and features linked to key ecosystem functions. We assessed the taxonomic diversity and functional trait structure of bird assemblages in undisturbed primary forest and fire-affected habitats undergoing natural regeneration, as well as areas of assisted natural regeneration, in Nyungwe National Park, Rwanda. We compiled bird occurrence data from point-count sampling, and obtained morphological traits for all species in our assemblages using measurements taken from wild birds and museum specimens. We found marked differences in species composition between primary forest habitats and regenerating forest, with similarity increasing over time since perturbation. Taxonomic diversity was higher in primary forest, and similar between the two restoration approaches. Functional diversity was lower in assisted naturally regenerated habitats, although separate analyses within dietary guilds revealed no differences across habitats. Among desired restoration outcomes, tree species diversity was the leading positive driver of avian species diversity, fern coverage exerted negative effects, while canopy cover had a positive but weak influence. Our findings underscore the importance of preventing anthropogenic fires in tropical rainforest since their impacts on ecological processes are not easily reversed, as shown by the lack of improvement in avian diversity metrics under assisted naturally regeneration in relation to natural regeneration. We stress the need to document both floral and faunal recovery in order to aid informed decision-making on restoration methods.
... Managing novel ecosystems effectively is a momentous challenge facing restoration ecologists and creating an integrated approach has proven elusive in most systems (Hobbs et al., 2014). Variation in disperser quality and in how they detect plants increases these challenges, but identification of these differences is critical in the creation of effective management plans across the globe (Farwig and Berens, 2012). Current management on Hawaiʻi, and elsewhere, is focused on the removal of invasive plants from restoration areas and out planting of native plants. ...
Seed dispersal is critical for maintaining ecosystem structure and over half of plant species worldwide rely on animals for dispersal. Animal-mediated seed dispersal requires tight links between animals and plants. The introduction of invasive species threatens this mutualism by potentially creating competition between native and invasive plants for dispersers and by altering the consumption of native fruits by introduced dispersers. Although the first critical step in seed dispersal is fruit consumption, we have limited knowledge of the characteristics that attract dispersers to a given plant. In particular, characteristics of the neighborhood surrounding a plant may alter frugivory and frugivores may vary in their responses to these characteristics. Identification of key neighborhood characteristics would help to identify the mechanisms which facilitate or limit seed dispersal, aiding in the management of species in novel ecosystems. We deployed camera traps on Oʻahu, Hawaiʻi to quantify how the total fruit abundance, percent invasive fruit, percent conspecific fruit, canopy cover, and ground vegetation density of the neighborhood influence visitation and fruit removal by introduced avian frugivores. Results showed that neighborhood effects had little influence on frugivory overall, but did influence avian foraging groups in disparate ways. In particular, visitation by arboreal foragers increased with canopy cover and the amount of fruit on the focal plant but decreased with higher neighborhood fruit abundance and more conspecific fruit. Ground forager visitation decreased with higher ground vegetation density and increased with more conspecific fruit. These findings suggest the neighborhood can be modified to facilitate arboreal foragers, which are higher quality dispersers on Oʻahu, and to limit ground foragers, which are primarily seed predators. We argue studies should consider differences among dispersers to adequately address the role of the neighborhood on frugivory in environments with multiple disperser species.
... Or, alternatively, in areas with high levels of seed predation and/or herbivory where dispersed propagules are unlikely to become established (McAlpine et al., 2016). Thus, this long-term study reinforces the notion that forest managers should consider both the environmental conditions determining tree recruitment as well as the biological processes that amplify plant fertilization and recruitment dynamics, such as seed dispersal or effective pollination (Farwig & Berens, 2012;Potts et al., 2016). ...
... Of this the dry forests account for nearly half of the world's tropical and subtropical forests [4]. Even though, in these forests anthropogenic disturbances are major threats to seed dispersal services and seedling survival leading to decline in plant community regeneration, demography and forest structure [5] in return interfering with seedling species richness and ecosystem services. Particularly because the germination and establishment of seedling of many species depends on the microclimate on the forest floor and below the canopy [6]. ...
The tropical regions have a rich diversity of tree species which provide the basis for a number of different forms and scales of economic activity. This study therefore was conducted with an aim of enhancing the knowledge of tree species diversity (seedlings and mature trees), and their relationship at the site. The experiment was laid out in three transects and quadrants in the forest: for mature trees the transects measured 100 m by 20 m, whereas for the seedlings quadrants measured 5 m by 5 m. That is along the ocean (T1), along human settlement (T2) and along the forest path (T3). Data was collected by counting mature trees species and seedlings. Data was analysed using R software 3.4.4 and results showed that a total of 22 tree species were recorded in the forest. In T1, the highest (22) species richness was recorded with 4 tree species restricted to the site (Bourellia nemoralis, Flueggia virosa, Turraea wakefieldii and Eryithrinia abyssinica). Combretum schumanii was most abundant in mature trees (89) followed by Lecaniodiscus fraxinifolius (36), Ochna thomasiana (21) and Adansonia digitata (14). All the above abundant species except Adanosnia digitata (2) were also abundant in seedlings with (189), (11) and (21) seedlings respectively. In T2, 9 tree species were recorded. Azadirachta indica was the most dominant in both mature trees (40) and seedlings (261) while Sterculia appendiculata recorded the lowest (1) and (0) respectively. T3 was rich with three exotic tree species namely Delonyx regia, Azadirachta digitata and Lannea schweinfurthii. Lecaniodiscus fraxinifolius was the most common with (35) followed by Combretum schumanii (11). While the seedlings were (23) and (67) respectively. In conclusion, it was evident that anthropogenic factors reduced species richness and the corag rag forest had more indeginous tree species and good seed recruitment.
... Frugivory and seed dispersal form an important mutualistic relationship (Farwig and Berens, 2012). Across many habitats, plants rely on frugivores to disperse seeds away from the parent (Janzen, 1970;Connell, 1971) and enhance germination and seedling establishment (Terborgh et al., 2002;Traveset et al., 2007). ...
Frugivory and seed dispersal contribute to the maintenance and regeneration of plant communities through transportation of seeds and enhancing germination through seed processing mechanisms. The effects of mammalian frugivore seed processing mechanisms on seed germination are generally well studied and the potential benefits include disinhibition (pulp removal), scarification (gut passage) and fertilisation (from faecal matrix). Nevertheless, our review found that there is bias in the comparative treatments included in seed dispersal studies through exclusion of entire fruit control groups and the fertiliser effect. In this study, we aimed to address such bias by using ecologically relevant experiments to investigate the influence of seed processing mechanisms on germination probability and latency of selected locally abundant fleshy-fruiting plant species, common in the diet of samango monkeys (Cercopithecus albogularis schwarzi), who are seed-spitters (disinhibition) and seed-swallowers (gut-passage and fertiliser effects). We designed experiments to isolate the cumulative effects of seed processing mechanisms and tested the effects of five treatments and one control treatment (entire fruit). We further assessed if exclusion of ecologically relevant seed treatments or relevant controls would affect our interpretation of the impact of the disperser on seed germination. Comparing gut passage and disinhibition indicated negative effects, whereas comparing gut passage and entire fruit controls indicated neutral effects in one species. Compared with gut passage alone, the fertiliser effects indicated positive or neutral benefits on germination probability. Our study demonstrated that the impacts of mammalian frugivores on germination may be under- or over-estimated in ecological literature where relevant treatments and meaningful controls are excluded.
... Loss of seed dispersers can have detrimental impacts on plant communities (Farwig and Berens 2012, Hansen and Galetti 2009, Melo et al. 2010. One of the most extreme examples of cascading effects of disperser loss on forest structure and function is from the tropical island of Guam in the Western Pacific. ...
Seed dispersal is an important ecological process that structures plant communities and influences ecosystem functioning. Loss of animal dispersers therefore poses a serious threat to forest ecosystems, particularly in the tropics where zoochory predominates. A prominent example is the near-total extinction of seed dispersers on the tropical island of Guam following the accidental introduction of the invasive brown tree snake ( Boiga irregularis ), negatively impacting seedling recruitment and forest regeneration. We investigated frugivory by a remnant population of Såli (Micronesian starling – Aplonis opaca ) on Guam and two other island populations (Rota, Saipan) to evaluate their ecological role as a seed disperser in the Mariana archipelago. Using a combination of behavioural observations, nest contents and fecal samples, we documented frugivory of 37 plant species. Native plants comprised the majority (66%) of all species and 90% of all seeds identified in fecal and nest contents. Diet was highly similar across age classes and sampling years. In addition, plant species consumed by Såli comprised 88% of bird-dispersed adult trees and 54% of all adult trees in long-term forest monitoring plots, demonstrating the Såli’s broad diet and potential for restoring native forests. Overall, we provide the most comprehensive assessment to date of frugivory by the Såli and confirm its importance as a seed disperser on Guam and throughout the Marianas.
Seeds removed by animals have one of two mutually exclusive fates – they are either predated or dispersed and still alive. The quality of seed dispersal by animals and the number of predated seeds will therefore determine net interaction outcomes for plants. Yet, it is poorly understood what proportion of removed seeds animals can predate before benefits of dispersal no longer outweigh costs of seed loss.
Here, we calculated the mutualism-antagonism continuum for seed removal of the fleshy-fruited tree Frangula alnus by the seed-predating bird Coccothraustes coccothraustes in Białowieża Forest. We integrated effects of the bird during seed dispersal (fruit handling, seed predation, and seed deposition) into microhabitat-structured tree population models.
Results of our models showed that the probability of a seed of F. alnus reaching maturity after seed removal by C. coccothraustes decreased from 0.0028% to 0% as seed predation increased from 0% to 100%. Seed removal was beneficial when less than 63.7% of seeds were predated, and antagonistic when more than 72.0% of seeds were predated. Modifying key model parameters (here, the negative effect of fruit pulp on seedling recruitment and the frequency of forest gaps) decreased and increased rates of seed predation, at which costs of seed loss outweighed benefits of seed dispersal (from 37.9% to 80.7%).
Our findings highlight that benefits of animal seed dispersal can largely outweigh costs of seed predation in a fleshy-fruited tree. Yet, the mutualism-antagonism continuum of seed removal depends on intrinsic factors (e.g. variation in interactions among individuals) and extrinsic factors (e.g. the environment) of seed dispersal and plant demography. Because C. coccothraustes was observed predating at least 80% of removed seeds, it appears to be an antagonist of animal-dispersed plants and exploiter of the seed dispersal mutualism.
Habitat destruction and fragmentation can change environmental conditions and disrupt mutualistic interactions, leading to impacts on natural populations. Here we checked how plant population structure responds to environmental degradation by quantifying effective seed dispersal and patterns of population distribution for the animal-dispersed palm Euterpe edulis Mart. (Arecaceae). Thus, we assessed E. edulis population structure at two locations with different degrees of fragmentation in the Interior Atlantic Forest (west of the State of Paraná, Brazil), where we registered the density of saplings at increasing distances from adults palms and from large trees in the vicinity (perch-trees). We found differences between locations, with aggregated saplings
Motivation
Biodiversity in many areas is rapidly declining because of global change. As such, there is an urgent need for new tools and strategies to help identify, monitor and conserve biodiversity hotspots. This is especially true for frugivores, species consuming fruit, because of their important role in seed dispersal and maintenance of forest structure and health. One way to identify these areas is by quantifying functional diversity, which measures the unique roles of species within a community and is valuable for conservation because of its relationship with ecosystem functioning. Unfortunately, the functional trait information required for these studies can be sparse for certain taxa and specific traits and difficult to harmonize across disparate data sources, especially in biodiversity hotspots. To help fill this need, we compiled Frugivoria, a trait database containing ecological, life‐history, morphological and geographical traits for mammals and birds exhibiting frugivory. Frugivoria encompasses species in contiguous moist montane forests and adjacent moist lowland forests of Central and South America—the latter specifically focusing on the Andean states. Compared with existing trait databases, Frugivoria harmonizes existing trait databases, adds new traits, extends traits originally only available for mammals to birds also and fills gaps in trait categories from other databases. Furthermore, we create a cross‐taxa subset of shared traits to aid in analysis of mammals and birds. In total, Frugivoria adds 8662 new trait values for mammals and 14,999 for birds and includes a total of 45,216 trait entries with only 11.37% being imputed. Frugivoria also contains an open workflow that harmonizes trait and taxonomic data from disparate sources and enables users to analyse traits in space. As such, this open‐access database, which aligns with FAIR data principles, fills a major knowledge gap, enabling more comprehensive trait‐based studies of species in this ecologically important region.
Main Types of Variable Contained
Ecological, life‐history, morphological and geographical traits.
Spatial Location and Grain
Neotropical countries (Mexico, Guatemala, Costa Rica, Panama, El Salvador, Belize, Nicaragua, Ecuador, Colombia, Peru, Bolivia, Argentina, Venezuela and Chile) with contiguous montane regions.
Time Period and Grain
IUCN spatial data: obtained February 2023, spanning range maps collated from 1998 to 2022. IUCN species data: obtained June 2019–September 2022. Newly included traits: span 1924 to 2023.
Major Taxa and Level of Measurement
Classes Mammalia and Aves; 40,074 species‐level traits; 5142 imputed traits for 1733 species (mammals: 582; birds: 1147) and 16 sub‐species (mammals).
Software Format
.csv; R.
Plant–animal interactions constitute some of the most important ecological processes for the maintenance of tropical forests. Bats are the only group of mammals capable of true flight and have been recognized as important dispersers of pioneer and secondary successional plant species. Although progress has been made in the study of Neotropical bats, morphological variation of the wing and its influence on niche separation between species is unknown. We evaluated relationships among habitat structures of selected Colombian tropical dry forest patches, the diet through interaction networks, and wing morphology of 11 species of bats in the Stenodermatinae subfamily (297 individuals) using geometric morphometry in a phylogenetic context. The results indicate that the phylogenetic signal for wing size is greater than for wing shape, thus providing some evidence for evolutionary convergence. Wing shape variation was associated primarily with the distal anatomical tip of the third finger and the joint between the humerus and the radius and ulna. Species with wide, short wings, as in the genus Artibeus had generalist diets and less nested positions within the interaction networks. In contrast, species with elongated and pointed wings, such as Sturnira and Platyrrhinus, had specialized diets and more nested positions within the interaction networks. We argue that wing shape variation may play an important role as a source of interspecific variation leading to food specialization within tropical bat communities.
Non‐human primate species are threatened worldwide. Their population declines go along with the loss of ecological functions such as seed dispersal that plays a crucial role in plant regeneration. Restoring essential habitat structures could thus not only protect primates, but also facilitate forest regeneration. We used classical vegetation description on the ground and a remote sensing analysis to describe habitat use of crowned lemurs ( Eulemur coronatus ), a seed‐dispersing primate endemic to northern Madagascar. Our aim was to find vegetation characteristics important for lemurs that might be targeted in a restoration approach. For this, we applied both methods in differently degraded forest types. Both classical vegetation description and remote sensing analysis were able to distinguish these forest types. The habitat use of our two study groups was associated consistently with vegetation structures measured on a small scale such as tree height and density of thick trees. In contrast, vegetation productivity and water content derived from satellite imagery on a larger scale could not consistently explain habitat use of lemurs. Thus, measurements on the ground can identify suitable microhabitats that do not show on the satellite imagery scale. These microhabitats might be very important conservation elements to create buffer zones and corridors. Further, they might attract seed‐dispersing species into degraded areas targeted for forest restoration, acting as natural regeneration nuclei. The potential of these microhabitats for conservation would not be recognized when analyses were based solely on landscape analyses on large scales.
Food-for-dispersal mutualisms are critical sources of energy flow in ecological networks. By providing a nutrient-rich reward in the form of a fruit or seed to an animal mutualist, plants gain directed dispersal. Myrmecochory is one form of animal-mediated seed dispersal in which ants are recruited to plant seeds by providing a nutrient rich appendage called an elaiosome. It is unclear to what impact nutrients provided by elaiosomes have on ants, and whether the mutualism can tolerate disruptions to this food source. In the Northeastern U.S. mixed deciduous forest ecoregion, a diverse assemblage of herbaceous plants are dispersed by Aphaenogaster ants. Since Aphaenogaster ants gain a significant nutrient subsidy from this mutualism, it is predicted that loss of these seeds could cause reductions in their population size. To test this hypothesis, I performed a long-term removal of elaiosome food sources for ants. All seeds were removed by hand from three 50m² plots, each paired with control plots with no removal, and a supplementation plot from April to May, from 2010 to 2012. Five years following removal treatments, I collected data on coverage of ant-dispersed plants and the abundance of seed-dispersing Aphaenogaster ants. Removal of all sources of elaiosomes resulted in modest reductions in the proportional coverage of ant-dispersed plants relative to control plots. Ant forager abundance was not impacted by the treatments five years after the removal of elaiosomes. In sum, Aphaenogaster populations may not always be limited by the availability of elaiosomes or myrmecochorous plants produce can recover quickly (<5 years) to provide enough food for these ants. As long as surrounding populations of understory forest plants are maintained, it appears that both mutualistic ants may rebound from a short-term reduction in the production of elaiosomes.
The PNN Selva de Florencia, in the central Andes of Colombia, is reservoir of a large biodiversity including five species of primates. Despite being a protected area, there are anthropic transformation processes that directly affect their ecosystems. Currently, we do not have quantitative models that allow us to estimate the effect of these transformations on primate populations. We evaluated the proportion of the area used (ψ), as an abundance estimation of the primates Ateles hybridus, Alouatta seniculus, and Cebus versicolor. Our methods included random sampling in 31 plots of 1 km2, where we evaluated i) primate presence; ii) human presence; as well as the percentage of: iii) plantations; iv) pastures; and v) natural coverage, using a 1:25 000 Corine Land Cover map, adapted to Colombia. We followed a Bayesian approach to analyze our dataset. We report a ψ of 0.16, and 0.14 detection probability for A. hybridus, with a decreasing area use in forest; a ψ of 0.83, and detection probability of 0.14 for A. seniculus, with a decreasing area use in plantations; finally, we estimated a ψ of 0.36, and 0.08 detection probability for C. versicolor, with a decreasing area use in plots with human presence. Data in our work can be used as input for the design and implementation of effective monitoring in this protected area.
Seed dispersal by frugivorous birds is a famous plant‐animal interaction. However, we demonstrated that frugivorous birds can disperse seeds of Ligustrum lucidum, and its seed parasite weevils and the parasitic wasps from the weevils in this study. The cryptic tetrad of Ligustrum‐disperser‐weevil‐wasp may be an overlooked phenomenon in seed dispersal syndrome.
Frugivorous birds play an important role in seed dispersal. Alien plant species’ seeds are dispersed by local birds in order to establish populations in new habitats. Alien plant species that produce fruits similar to that of native species have the potential to attract local birds, creating new mutualistic systems that are similar to the local ones. In autumn 2018 and 2019, we studied the seed dispersal systems of an alien plant species, Phytolacca americana, and a native species, Cayratia japonica, in a coastal seawall forest. Both plant species’ fruit, frugivorous bird foraging behaviors, seed germination rates, and seedling microhabitats were examined to determine whether the alien species had a similar seed dispersal system to that of the native species. Our results showed that P. americana and C. japonica had similar fruit type, color, and ripening period. There was a positive correlation between the percentage rate of fruit ripening and the percentage rate of fruit missing for both plant species, indicating that local frugivorous birds have the potential to sufficiently disperse the alien seeds to enable its spread in the coastal seawall forest (simple linear regression, P. americana: β = 0.863 ± 0.017, R2adj = 0.978, P
生态群落中不同物种间发生多样化的相互作用, 形成了复杂的种间互作网络。复杂生态网络的结构如何影响群落的 生态系统功能及稳定性是群落生态学的核心问题之一。 种间互作直接影响到物质和能量在生态系统不同组分之间的流动和循 环以及群落构建过程, 使得网络结构与生态系统功能和群落稳定性密切相关。在群落及生态系统水平上开展种间互作网络研 究将为群落的构建机制、生物多样性维持、生态系统稳定性、物种协同进化和性状分化等领域提供新的视野。当前生物多样 性及生态系统功能受到全球变化的极大影响, 研究种间互作网络的拓扑结构、构建机制、稳定性和生态功能也可为生物多样 性的保护和管理提供依据。该文从网络结构、构建机制、网络结构和稳定性关系、种间互作对生态系统功能的影响等4个方 面综述当前种间网络研究进展, 并提出在今后的研究中利用机器学习和多层网络等来探究环境变化对种间互作网络结构和 功能的影响, 并实现理论和实证研究的有效整合。
Varied species interactions form complex species interaction networks in diverse ecological communities. Understanding how the network structure affects ecosystem functions and community stability is one major issue for community ecology. Species interactions can directly affect the flow and circulation of matter and energy among different components of ecosystems. As a result, the network structure is closely related to the structure, stability, and functioning of ecological communities. Prior studies on interaction networks have shed light on community assembly, biodiversity maintenance, ecosystem stability, coevolution and trait diversification. Currently, biodiversity and ecosystem functions have been largely affected by global environmental changes. The interaction networks and their relationship with biodiversity loss in a changing world have become important research topics. Exploring the structure and assembly of species interaction networks, stability, and ecosystem functions is significant for understanding the maintenance mechanism and biodiversity conservation. Here, we reviewed the reserach advances in the structure of ecological networks and their determinants, network stability, the relationship between network and ecosystem functions, and the mechanisms underlying these relationships. We also suggest future research directions on how to apply machine learning and multilayer network to disentangle the effects of environmental change on network structure and ecosystem functions by integrated theoretical and empirical studies.
Dispersal limitation severely impairs the trajectory of restoration, mainly due to the lack of seed vectors bringing seeds from nearby habitats; a role played by many frugivorous vertebrates that can be absent or reduced in restored or degraded sites.
Here we propose a new technique named Induced Seed Dispersal, that amplifies the role that many generalist frugivores have in seed dispersal. It consists in the offering of seeds embedded in the pulp of commercial fruits or whole native fleshy fruits in feeders to generalist frugivores, which ingest the seeds and defecate them elsewhere. We set feeders in a restored site and monitored the visiting pattern of these frugivores with cameras‐traps. We also set seed traps to retrieve seeds dispersed by frugivores and offered around 1,500 seeds of Cecropia hololeuca (Urticaceae) per week for 1 year.
We recorded at least 24 generalist frugivore species of terrestrial mammals, bats and birds, which ingested/removed the seeds/fruits from the feeders. Seeds of C. hololeuca dispersed by marmosets were retrieved in the seed traps and germinated. We estimated a potential seed rain of more than 600 C. hololeuca seeds ha ⁻¹ mo ⁻¹ .
Synthesis and applications . Our study demonstrates that this new technique can make use of generalist frugivores to assist restoration or regeneration into sites where seed dispersal is compromised by the lack of dispersers or limited seed arrival. Inducing seed dispersal by generalist frugivores is a low‐cost and easy‐managed technique that can be applied year‐round in restoration and forest enrichments at all scales.
Genetic considerations are rarely applied in forest conservation management strategies, but forest fragmentation can reduce pollen and seed dispersal both between and within isolated fragments. Gene flow and immigration rates determine the extent to which individual plants are related to each other at different distances from themselves. This gradation in relatedness is known as a population's fine scale spatial genetic structure (SGS). Specifically, reduced but clumped immigration from distant fragments reduces fine scale SGS, whereas reduced gene flow within fragments increases fine scale SGS. In addition, non-random mortality caused by post-dispersal ecological processes can also affect SGS. We studied the effects of fragmentation on the fine scale SGS of Ficus species with different habitat preferences and distributional ranges in an archipelago of South African forest patches. Significant fine scale SGS present in all three species suggests gene dispersal is restricted, even within forest fragments, probably due to localised seed dispersal. An endemic forest specialist, F. bizanae, has an unusually high fine scale SGS for a monoecious Ficus. This may be explained by several features that reduce pollen dispersal distances and are more typical of dioecious Ficus. A significant negative kinship coefficient in one F. bizanae population suggests that clumped long-distance immigration may have occurred in the past. Significant fine scale SGS in adult but not juvenile F. craterostoma suggests that recent population fragmentation has negatively affected long-distance immigration. Supplementation of F. craterostoma gene flow would maintain its genetic diversity. In contrast, the limited range of F. bizanae may result from its pollinator’s behavior, rather than specific habitat requirements and ensuring its long-term survival may require artificial introductions to other forests.
Question
Human‐mediated dispersal (HMD) comprises human‐vectored dispersal (HVD; direct movement of organisms by people) and human‐altered dispersal (HAD; indirect change in dispersal patterns through human alteration of ecosystems). In the vegetation dynamics literature, human influence has primarily been studied in terms of perturbations to natural communities. Except for non‐native invasions, the role of HMD in vegetation dynamics has rarely been considered. Given the increasing human population and its pervasive impacts across the World, it is necessary to understand the different ways in which HMD drives changes in vegetation dynamics. Importantly how large are these influences and how do they disrupt natural processes?
Methods
We reviewed studies examining aspects of HMD in relation to vegetation dynamics, and used the broader literature to inform a conceptual synthesis of the impacts of HMD on vegetation dynamics.
Results & Conclusions
The propensity to be affected by HMD varies among species, and this is related to seed and plant traits. Together, these effects combine to determine whether HMD disrupts or enhances seed dispersal into a community. The ultimate consequences of changed arrival of seeds into a community is determined by the strength of the environmental and biotic filters, which govern the establishment and persistence of species. The effect of accidental HVD depends whether it follows the same rules as for natural dispersal; indeed humans might replace lost natural dispersers and thus enhance community resilience. Intentional HVD through sowing or planting, will generally be highly disruptive especially as it often involves associated management. Traditionally, HAD has been considered to disrupt vegetation dynamics through, e.g., fragmentation or loss of natural dispersers. But, an HMD perspective can inform actions related to HAD that increase resilience, e.g. green infrastructure or vegetation management. Our framework encourages researchers to consider HMD holistically, to understand how the increasing human footprint might affect vegetation dynamics and resilience under future change.
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ABSTRACT:
In the face of limited funding, knowledge, and time for action, conservation efforts often rely on shortcuts for the maintenance of biodiversity. The umbrella species concept - proposed as a way to use species requirements as a basis for conservation planning-has recently received growing attention. We reviewed the literature to evaluate the concept's general usefulness. An umbrella species is defined as a species whose conservation is expected to confer protection to a large number of naturally co-occurring species. This concept has been proposed as a tool for determining the minimum size for conservation areas, selecting sites to be included in reserve networks, and setting minimum standards for the composition, structure, and processes of ecosystems. Among the species suggested as potential umbrellas, most are large mammals and birds, but invertebrates are increasingly being considered. Eighteen research papers, most of which were based on hypothetical reserves or conservation networks, have provided evaluations of umbrella species schemes. These show that single-species umbrellas cannot ensure the conservation of all co-occurring species because some species are inevitably limited by ecological factors that are not relevant to the umbrella species. Moreover, they provide evidence that umbrella species from a given higher taxon may not necessarily confer protection to assemblages from other taxa. On the other hand, multi-species strategies based on systematic selection procedures (e. g., the focal species approach) offer more compelling evidence of the usefulness of the concept. Evaluations of umbrella species schemes could be improved by including measures of population viability and data from many years, as well as by comparing the efficiency of the proposed scheme with alternative management strategies.
New Zealand's offshore and outlying islands have long been a focus of conservation biology as sites of local endemism and as last refuges for many species. During the c. 730 years since New Zealand has been settled by people, mammalian predators have invaded many islands and caused local and global extinctions. New Zealand has led international efforts in island restoration. By the late 1980s, translocations of threatened birds to predator-free islands were well under way to safeguard against extinction. Non-native herbivores and predators, such as goats and cats, had been eradicated from some islands. A significant development in island restoration in the mid-1980s was the eradication of rats from small forested islands. This eradication technology has been refined and currently at least 65 islands, including large and remote Campbell (11 216 ha) and Raoul (2938 ha) Islands, have been successfully cleared of rats. Many of New Zealand's offshore islands, especially those without predatory mammals, are home to large numbers of breeding seabirds. Seabirds influence ecosystem processes on islands by enhancing soil fertility and through soil disturbance by burrowing. Predators, especially rats, alter ecosystem processes and cause population reductions or extinctions of native animals and plants. Islands have been promoted as touchstones of a primaeval New Zealand, but we are now increasingly aware that most islands have been substantially modified since human settlement of New Zealand. Archaeological and palaeoecological investigations, together with the acknowledgement that many islands have been important mahinga kai (sources of food) for Māori, have all led to a better understanding of how people have modified these islands. Restoration technology may have vaulted ahead of our ability to predict the ecosystem consequences of its application on islands. However, research is now being directed to help make better decisions about restoration and management of islands, decisions that take account of island history and key drivers of island ecosystem functioning.
Throughout the tropics, mammalian seed dispersers are being driven to local extinction by intense hunting pressure, generating concern not only about the loss of these species, but also about the consequences for the plants they disperse. We compared two rain forest sites in Cameroon-one with heavy hunting pressure and one protected from hunting-to appraise the loss of mammalian seed dispersers and to assess the impact of this loss on seed removal and seed dispersal of Antrocaryon klaineanum (Anacardiaceae), a mammal-dispersed tree. Surveys of arboreal frugivores indicate that three of the five monkey species, as well as chimpanzee and gorilla, have been extirpated from the hunted forest. Diaspore counts underneath A. klaineanum adults (six trees per site) indicate that seed removal is severely reduced in the hunted forest. Finally, genetic maternity exclusion analysis (using 3-7 nuclear microsatellite loci) of maternally inherited endocarp tissue from diaspores collected under the canopies of 12 fruiting "mother" trees (six trees per site) revealed that seed dispersal in the hunted forest is also greatly reduced. In the hunted forest with reduced mammal dispersal agents, only 1 of the 53 assayed endocarps (2%) did not match the mother and was determined to be from a dispersed diaspore. By contrast, in the protected forest, 20 of the 48 assayed endocarps (42%) were from dispersed diaspores. This study provides strong evidence that loss of dispersal agents can lead to reduced seed removal and loss of seed dispersal, disrupting the seed dispersal cycle.
Dispersal-viewed as the departure of a diaspore (eg. seed or fruit) from the parent plant-is examined in terms of mechanisms, advantages (eg. in connection with escape from parental influence, and colonization), and patterns of production (eg. geographical aspects, seasonality, and intraspecific variation).-P.J.Jarvis
1. In June to September 1993 a transhumant flock of sheep on the Schwabische Alb was examined with respect to which plants and animals are transported on and in the wool of sheep within calcareous grasslands. Several factors possibly influencing the attachment and detachment of diaspores on fleeces were studied, as well as the distribution of diaspores on the various body-parts of a sheep. The effects of different modes of sheep locomotion on dispersal were examined with the help of a sheep dummy. In order to assess the retention time of diaspores and animals on sheep, some experiments with marked diaspores and animals were carried out on two tamed sheep. 2. In 16 intensive examinations of the fleece of a single sheep, over 8500 diaspores of 85 vascular plants species were found. The highest numbers of diaspores were attached at the breast and neck of the sheep. 3. Height of diaspore presentation, surface structure of diaspores and sheep locomotion were found to be the decisive factors for the reception and transport of diaspores in the wool. In addition, plant frequency and the length of the disseminating period are of importance. 4. Marked diaspores with both adhesive and smooth surfaces remained on the sheepskin for up to seven months, and can consequently be dispersed over the entire roaming area of the sheep. 5. Amongst the animals transported by sheep, only grasshoppers (13 species) were observed frequently on the flock of sheep. The period of time marked grasshoppers stayed on sheep ranged from 1 to 69 min, with an average of 14 min. During this period sheep can cover distances of over 100 m when grazing and well over 500 m when roaming. 6. Our study indicates that the importance of the dispersal of diaspores, and especially animals, by animals has so far been largely underestimated. This is mostly due to the methods previously used to examine dispersal mechanisms. 7. Conservation management of rare and endangered species should consider the importance of sheep for maintaining the species richness of calcareous grasslands. It is likely that transhumant sheep farming is irreplaceable in the restoration of grasslands threatened by fallow and woody successional stages. Moreover, traditional shepherding facilitates the exchange of individuals of both plants and animals between isolated patches. That is, sheep are able to maintain dynamic processes even in our greatly fragmented landscape: this is probably essential to long-term population viability of many species.
What are birds worth—what is their actual dollar value to human society? To most of us in the ornithological community, birds are invaluable. But in these times we need more specific ra-tionales to convince policy makers and business leaders to include bird conservation in land-use and development decisions. Over the past two decades, awareness of our dependence on a variety of ecosystem services (natural ecological processes that benefit human society) and of their importance and prevalence has pro-gressed toward the goal of making conservation a mainstream value (Ehrlich and Kennedy 2005, Perrings et al. 2010, Rands et al. 2010, Sodhi and Ehrlich 2010). Building strategies for the protec-tion of ecosystem services into conservation and land-use plan-ning is essentially the promotion of human survival, although many policy makers misinterpret conservation efforts as luxury. Several previous reviews have identified ecosystem services that benefit human society (Costanza et al. 1997, Daily 1997, Pimentel et al. 1997, Sekercioglu 2010). The challenge, however, is to calcu-late the value of ecosystem services in meaningful and relevant ways that can be used to justify the protection of ecosystem ser-vices in land-use recommendations and policy decisions (Daily et al. 2000, 2009). As the case studies below illustrate, recent work on the ecosystem services provided by birds has made good prog-ress toward this goal, but much remains to be done. Our objec-tives here are to describe the ecosystem services provided by birds,
Monitoring of exposure to pesticides in many countries shows extensive exposure of predators to anticoagulant rodenticides, which are used to control rats. Many predators and scavengers are declining in numbers, and exposure to rodenticides might therefore be of importance in conservation biology.
Predators and scavengers of poisoned rats are at most risk of secondary poisoning. However, several predatory species of conservation concern rarely eat rats, implicating non‐target small mammals as the major route of exposure. For the first time, this research investigated the importance of non‐target small mammals as routes of exposure to rodenticide for predators and scavengers in the UK.
Exposure studies of non‐target small mammals were carried out alongside routine rat control at five sites, around agricultural buildings ( n = 2) and feed hoppers for game birds ( n = 3).
Three non‐target rodent species fed on rodenticide from bait boxes during routine rat control treatments. A large proportion (48·6%) of individuals in local populations ate the bait: woodmice Apodemus sylvaticus were most exposed, followed by bank voles Clethrionomys glareolus then field voles Microtus agrestis .
Local populations of non‐target small mammals declined significantly following rodenticidal rat control but their relative proportions did not change significantly. Populations recovered partially after 3 months, depending on the time of the year relative to the breeding cycle.
Synthesis and applications. Our results clearly demonstrate that routine rat control reduced local populations of non‐target small mammals. This may limit the food supply of some specialist predators. Most importantly, this demonstrates a significant route of exposure of predators and scavengers of small mammals to secondary poisoning. Rodenticides are applied on farms and game estates across the UK. Hence the results of this study are indicative of non‐target rodenticide exposure nationally. Mitigation requires a shift from the current reliance on rodenticides to ecologically based rodent management, involving improvements in site management and the adoption of good farming practice.
Tropical forests are being lost at an alarming rate. Studies from various tropical locations report losses of forest birds as possibly direct or indirect results of deforestation. Although it may take a century for all the sensitive species to be ex-tirpated from a site following habitat loss, species with larger or heavier bodies and those foraging on insects, fruits, or both are particularly extinction prone. Larger-or heavier-bodied species may occur at low densities, increasing their vulnerability to habitat alterations. Insectivores are vulnerable for reasons such as the loss of preferred microhabitats, poor dispersal abilities, and/or ground nesting habits that make them susceptible to predation. The lack of year-round availability of fruits may make survival in deforested or fragmented areas difficult for frugivores. Extirpation of large preda-tors, superior competitors, pollinators, and seed dispersers may have repercussions for tropical ecosystem functioning. Large tropical reserves that adequately protect existing forest avifauna are needed. Sound ecological knowledge of tropical forest avifauna for biodiversity-friendly forest management practices is also needed but sorely lacking.
About 45 palm species occur in the Atlantic forest of Brazil, and most of them are affected by loss of seed dispersers resulting from forest fragmentation and hunting. Here we report the effects of habitat loss and defaunation on the seed dispersal system of an endemic palm, Astrocaryum aculeatissimum . We evaluated seed removal, insect and rodent seed predation, and scatter-hoarding in nine sites, ranging from 19 ha to 79 000 ha. We report the seedling, juvenile and adult palm densities in this range of sites. Endocarps remaining beneath the parent palm had a higher probability of being preyed upon by insects in small, mostly fragmented and more defaunated sites. The frequency of successful seed removal, scatter-hoarding and consumption by rodents increased in the larger, less defaunated sites. Successful removal and dispersal collapsed in small (< 1000 ha), highly defaunated sites and frequently resulted in low densities of both seedlings and juveniles. Our results indicate that a large fraction of Atlantic forest palms that rely on scatter-hoarding rodents may become regionally extinct due to forest fragmentation and defau-nation. Current management practices including palm extraction and hunting pressure have a lasting effect on Atlantic forest palm regeneration by severely limiting successful recruitment of prereproductive individuals.
Wild animals have been a source of food and income through subsistence hunting by forest-dwelling people in Neotropical countries
in spite of the fact that hunting appears to be unsustainable as it leads to the depletion of wild fauna. Laws in Brazil and
other Latin American countries forbid hunting but allow the commercial use of captive-bred animals. Notwithstanding the fact
that this is a controversial topic among conservationists, in this paper we propose that wildlife farming in the Neotropics
can be an alternative to the over-hunting and deforestation that are carried out for the production of traditional food and
pastures for livestock. This review sets out this proposal, and discusses the implications for tropical forest integrity and
rural population dependency on forest resources. We discuss the ecological and economical advantages of wildlife farming and
its constraints as a conservation tool, using collared peccary (Pecari tajacu) farming in the Amazon region as a model. Productivity levels may reach 19,000 times higher than those obtained from the
management of peccaries from forests in the Amazon region. This can be achieved with an easily obtainable diet composed of
forest fruits and locally available agricultural by-products. Therefore, establishing captive management programs for peccaries
is an effective way of avoiding wild stock depletion, deforestation, and guaranteeing the livelihood of forest dwellers in
the Neotropics. However, it is essential that governmental and/or non-governmental agencies be involved in providing subsides
to establish peccary farms, provide technical assistance, and introducing peccary captive breeding centers to supply founder
stock.
KeywordsCaptive breeding–Food security–Rearing of game–Wildlife husbandry
Seed dispersal mechanisms should have a direct impact on the genetic structure of populations. Species whose seeds are dispersed near the maternal plant (e.g. gravity or wind dispersal) or species whose seeds are deposited in clumps or patches should have more fine-scale genetic structure than species whose seeds are dispersed singly by mobile animals. Furthermore, due to the overlap of seed shadows, species with high adult densities should have less genetic structure than species with lower densities. Allozyme analyses of three tropical tree species belonging to the moist tropical forest of Barro Colorado Island, Republic of Panama, were used to describe variation in the scale and intensity of genetic structure within their populations. The genetic structure of seedlings and immature trees in the low-density, wind-dispersed species (Platypodium elegans) was the coarsest and strongest whereas genetic structure in a population of Swartzia simplex var. ochnacea (high density, bird-dispersed) was both the finest and the weakest. The genetic structure of Alseis blackiana, a high-density, wind-dispersed species was intermediate in both degree and scale. In P. elegans and A. blackiana, which had J shaped size distributions, the significant genetic structure seen in the smaller and intermediate diameter classes disappeared in the largest diameter class. The loss of genetic structure was not observed in S. simplex, a species with a more even size distribution.
Human activities such as fragmentation and selective logging of forests can threaten population viability by modification of ecological and genetic processes. Using six microsatellite markers, we examined the effects of forest fragmentation and local disturbance on the genetic diversity and structure of adult trees (N = 110) and seedlings (N = 110) of Prunus africana in Kakamega Forest, western Kenya. Taking samples of adults and seedlings allowed for study of changes in genetic diversity and structure between generations. Thereby, adults reflect the pattern before and seedlings after intensive human impact. Overall, we found 105 different alleles in the six loci examined, 97 in adults and 88 in seedlings. Allelic richness and heterozygosity were significantly lower in seedlings than in adults. Inbreeding increased from adult tree to seedling populations. Genetic differentiation of adult trees was low (overall F
ST = 0.032), reflecting large population sizes and extensive gene flow in the past. Genetic differentiation of seedlings was slightly higher (overall F
ST = 0.044) with all of the 28 pairwise F
ST-values being significantly different from zero. These results suggest that human disturbance in Kakamega Forest has significantly reduced allelic richness and heterozygosity, increased inbreeding and slightly reduced gene flow in P. africana in the past 80–100 years.
Vertebrate responses to hunting are widely variable for target and nontarget species depending on the history of hunting and productivity of any given site and the life history traits of game species. We provide a comprehensive meta-analysis of changes in population density or other abundance estimates for 30 mid-sized to large mammal, bird and reptile species in 101 hunted and nonhunted, but otherwise undisturbed, Neotropical forest sites. The data set was analyzed using both an unnested approach, based on population density estimates, and a nested approach in which pairwise comparisons of abundance metrics were restricted to geographic groups of sites sharing similar habitat and soil conditions. This resulted in 25 geographic clusters of sites within which 1811 population abundance estimates were compared across different levels of hunting pressure. Average nested changes in abundance across increasingly greater levels of hunting pressure ranged from moderately positive to highly negative. Populations of all species combined declined across greater differences in hunting pressure by up to 74.8 percent from their numeric abundance in less intensively hunted sites, but harvest-sensitive species faired far worse. Of the 30 species examined, 22 declined significantly at high levels of hunting. Body size significantly affected the direction and magnitude of abundance changes, with large-bodied species declining faster in overhunted sites. Frugivorous species showed more marked declines in abundance in heavily hunted sites than seed predators and browsers, regardless of the effects of body size. The implications of hunting for seed dispersal are discussed in terms of community dynamics in semi-defaunated tropical forests.
This paper reviews the characteristics of animal seed dispersal relevant to tropical forest restoration efforts and discusses their management implications. In many tropical regions seed dispersal by animals is the predominant form of dissemination of propagules and has the potential to facilitate recolonization of native vegetation on degraded sites. The site traits relevant for attracting seed dispersers include the availability of perches, the structural complexity of the vegetation and the presence of food resources, especially fruit, as an attractant. Tree plantations with these traits will be particularly attractive to animal seed dispersers and, therefore, will have higher rates of seed rain than plantations lacking these traits. The efficacy of animal seed dispersal to restoration sites can be limited by the degree of isolation from a seed source, absence of animal seed dispersers in the region and by large seed size. In highly degraded regions, where seed sources may be isolated and animal seed dispersers rare, restoration will require direct seeding or planting. However, even under the best of conditions with a full compliment of animal seed dispersers and a nearby seed source, large-seeded species, because of their relative immobility, should be planted if a full return to primary forest is desired.
As the need increases for sound estimates of impending rates of animal and plant species extinction, scientists must have a firm grounding in the qualitative and quantitative methods required to make the best possible predictions. Extinction Rates offers the most wide-ranging and practical introduction to those methods available. With contributions from an international cast of leading experts, the book combines cutting-edge information on recent and past extinction rates with treatments of underlying ecological and evolutionary causes. Throughout, it highlights apparent differences in extinction rates among taxonomic groups and places, aiming to identify unresolved issues and important questions. Written with advanced undergraduate and graduate students in mind, Extinction Rates will also prove invaluable to researchers in ecology, conservation biology, and the earth and environmental sciences.
This is the second edition of a multi-author book first published in 1992. It deals with all aspects of plant regeneration by seeds, including reproductive allocation, seed dispersal and predation, longevity, dormancy and germination. All chapters have been updated, and four new chapters added on seed size, seedling establishment, the role of gaps, and regeneration from seed after fire.
As anthropogenic environmental changes spread and intensify across the planet, conservation biologists have to analyze dynamics at large spatial and temporal scales. Ecological and evolutionary processes are then closely intertwined. In particular, evolutionary responses to anthropogenic environmental change can be so fast and pronounced that conservation biology can no longer afford to ignore them. To tackle this challenge, areas of conservation biology that are disparate ought to be integrated into a unified framework. Bringing together conservation genetics, demography, and ecology, this book introduces evolutionary conservation biology as an integrative approach to managing species in conjunction with ecological interactions and evolutionary processes. Which characteristics of species and which features of environmental change foster or hinder evolutionary responses in ecological systems? How do such responses affect population viability, community dynamics, and ecosystem functioning? Under which conditions will evolutionary responses ameliorate, rather than worsen, the impact of environmental change?
Myrmecochorous dispersal distances are reviewed; the seed dispersal curve generated by ants shows a characteristic peak at short distances and a long tail, a shape suited to small densities of safe sites. Mean global distance is of 0.96 m (n = 2524) with a range of 0.01-77 m. Data have been broken down by geography (Northern hemisphere v. Southern hemisphere), taxonomy (ant subfamilies) and ecology (vegetation: sclerophyllous v. mesophyllous). Although a statistical difference exists between dispersal curves from the Northern hemisphere and the Southern hemisphere, this may be an artefact of lack of data from mesophyllous myrmecochores from this hemisphere. The four ant subfamilies do show also numerical differences but could not be subjected to statistical analysis. A difference between the shape of dispersal curve for sclerophyllous myrmecochores and mesophyllous myrmecochores has also been detected. We hypothesize that this difference is related to the myrmecological communities from both types of vegetation: dispersing ants from sclerophyllous vegetation would have smaller nest densities and/or bigger foraging areas than dispersing ants from mesic environments.
Seed dispersal mechanisms should have a direct impact on the genetic structure of populations. Species whose seeds are dispersed near the maternal plant (e.g. gravity or wind dispersal) or species whose seeds are deposited in clumps or patches should have more fine-scale genetic structure than species whose seeds are dispersed singly by mobile animals. Furthermore, due to the overlap of seed shadows, species with high adult densities should have less genetic structure than species with lower densities. Allozyme analyses of three tropical tree species belonging to the moist tropical forest of Barro Colorado Island, Republic of Panama, were used to describe variation in the scale and intensity of genetic structure within their populations. The genetic structure of seedlings and immature trees in the low-density, wind-dispersed species (Platypodium elegans) was the coarsest and strongest whereas genetic structure in a population of Swartzia simplex var. ochnacea (high density, bird-dispersed) was both the finest and the weakest. The genetic structure of Alseis blackiana, a high-density, wind-dispersed species was intermediate in both degree and scale. In P. elegans and A. blackiana, which had ‘J’ shaped size distributions, the significant genetic structure seen in the smaller and intermediate diameter classes disappeared in the largest diameter class. The loss of genetic structure was not observed in S. simplex, a species with a more even size distribution.
Myrmecochorous dispersal distances are reviewed; the seed dispersal curve generated by ants shows a characteristic peak at short distances and a long tail, a shape suited to small densities of safe sites. Mean global distance is of 0.96 m (n= 2524) with a range of 0.01–77 m. Data have been broken down by geography (Northern hemisphere v. Southern hemisphere), taxonomy (ant subfamilies) and ecology (vegetation: sclerophyllous v. mesophyllous). Although a statistical difference exists between dispersal curves from the Northern hemisphere and the Southern hemisphere, this may be an artefact of lack of data from mesophyllous myrmecochores from this hemisphere. The four ant subfamilies do show also numerical differences but could not be subjected to statistical analysis. A difference between the shape of dispersal curve for sclerophyllous myrmecochores and mesophyllous myrmecochores has also been detected. We hypothesize that this difference is related to the myrmecological communities from both types of vegetation: dispersing ants from sclerophyllous vegetation would have smaller nest densities and/or bigger foraging areas than dispersing ants from mesic environments.
We compare the dispersal spectra of diaspores from varied plant communities in Australia, New Zealand, and North America, assigning dispersal mode to each diaspore type on the basis of apparent morphological adaptations. Species with ballistic and external dispersal modes were uncommon in most communities we surveyed. Ant dispersal was also rather uncommon, except in some Australian sclerophyll vegetation types. The frequency of vertebrate dispersal ranged up to 60% of the flora, the highest frequencies occurring in New Zealand forests. Wind dispersal ranged as high as 70% of the flora, with the highest values in Alaska, but usually comprised 10–30% of the flora. Many species in most communities had diaspores with no special morphological device for dispersal. Physiognomically similar vegetation types indifferentbiogeographic regions usually had somewhat dissimilar dispersal spectra. The frequency of dispersal by vertebrates often increased and the frequency of species with no special dispersal device decreased along gradients of increasing vertical diversity of vegetation structure. Elevation and moisture gradients also exhibited shifts in dispersal spectra. Within Australia, vertebrate‐ and wind‐dispersal increased in frequency along a soil‐fertility gradient, and dispersal by ants and by no special device decreased. Habitat breadths (across plant communities) and microhabitat breadths (within communities) for species of each major dispersal type did not show consistent differences, in general. Ant‐dispersed species often had lower cover‐values than other species in several Australian vegetation types.
We discuss the ecological bases of these differences in dispersal spectra in terms of the availability of dispersal agents, seed size, and other ecological constraints. Seed size is suggested to be one ecological factor that is probably of general relevance to the evolution of dispersal syndromes.
Iridomyrmex humilis has recently invaded areas of Cape fynbos and displaced the dominant native ants. Iridomyrmex differed from native ants in being slower to discover the seeds (morphologically achenes) of ant-dispersed Mimetes cucullatus (Proteaceae), in moving them shorter distances, and in failing to store them in nests below the soil. Seeds left on the soil surface were eaten by vertebrate and invertebrate predators. Seed depots were established and then the area was burned. Emergence was 35.3% in sites not infested by Iridomyrmex and 0.7% in infested sites. Seedlings in naturally occurring stands of M. cucullatus burnt in the same fire were widely distributed in noninfested sites, but were fewer and were confined within the canopy radius in infested sites. Continued invasion of fynbos by Iridomyrmex may eventually lead to extinction of many rare, endemic Cape Proteaceae by slow and subtle attrition of seed reserves. -from Authors
Invasions of natural communities by non‐indigenous species threaten native biodiversity and are currently rated as one of the most important global‐scale environmental problems. The mechanisms that make communities resistant to invasions and drive the establishment success of seedlings are essential both for management and for understanding community assembly and structure. Especially in grasslands, anecic earthworms are known to function as ecosystem engineers, however, their direct effects on plant community composition and on the invasibility of plant communities via plant seed burial, ingestion and digestion are poorly understood.
In a greenhouse experiment we investigated the impact of Lumbricus terrestris , plant functional group identity and seed size of plant invader species and plant functional group of the established plant community on the number and biomass of plant invaders. We set up 120 microcosms comprising four plant community treatments, two earthworm treatments and three plant invader treatments containing three seed size classes.
Earthworm performance was influenced by an interaction between plant functional group identity of the established plant community and that of invader species. The established plant community and invader seed size affected the number of invader plants significantly, while invader biomass was only affected by the established community. Since earthworm effects on the number and biomass of invader plants varied with seed size and plant functional group identity they probably play a key role in seedling establishment and plant community composition.
Seeds and germinating seedlings in earthworm burrows may significantly contribute to earthworm nutrition, but this deserves further attention. Lumbricus terrestris likely behaves like a ‘farmer’ by collecting plant seeds which cannot directly be swallowed or digested. Presumably, these seeds are left in middens and become eatable after partial microbial decay. Increased earthworm numbers in more diverse plant communities likely contribute to the positive relationship between plant species diversity and resistance against invaders.
Human disturbance threatens and modifies forest ecosystems worldwide. Previous studies have investigated the effects of human impact on local bird communities in disturbed forests, but we still lack information on how bird species richness and ecological processes respond to different forest modifications present at a landscape scale. In a heterogeneous South African landscape, we chose six types of indigenous scarp forest, differing in the intensity of human disturbance: continuous natural forests and natural forest fragments in nature reserves, forest fragments in eucalyptus plantations, fragments in the agricultural matrix, forest gardens and secondary forests in game reserves. In 36 study sites, we investigated the bird community using point counts and observed the seed removal of birds at the native tree species Celtis africana. Species richness did not differ among the forest types, but abundance varied significantly with most birds observed in fragments in the agricultural matrix, forest gardens, and secondary forests. The higher bird abundance in these forests was mainly due to forest generalists, shrubland and open country species whereas forest specialists were rarely present. Changes in species composition were also confirmed by multivariate analysis which clearly separated bird communities by forest type. Frugivore abundance in C. africana was highest in natural forest fragments, fragments in the agricultural matrix, forest gardens and secondary forests. The same trend was found for the estimated total number of fruits removed per C. africana tree, though the differences among forest types were not significant. Consequently, modified forests seem to maintain important ecological functions as they provide food sources for generalist species which may, due to their mobility, enhance natural plant regeneration. However, we could show that protected forest habitats are important refugees for specialist species sensitive to human disturbance.
Fruiting trees in degraded areas are attractive for frugivorous birds and may become centers of regeneration. However, a number of tree species in degraded areas are exotic species. Thus, the question arises whether these exotic species can also act as foci for forest regeneration. In the farmland adjacent to Kakamega Forest, Kenya, we investigated the frugivore assemblage in, and seed rain and seedling establishment under, 29 fruiting exotic guava trees (Psidium guajava) at different distances to the forest. The results show that 40 frugivorous bird species visited guava trees. All of the seed and 82 percent of the seedling species found under the treecrowns were animal dispersed, 58 and 57 percent of them late-successional species, respectively. Path analysis revealed that the abundance of frugivorous birds, seeds, and seedlings did not decrease up to a distance of 2 km from the forest. Surprisingly, the abundance of frugivorous shrubland birds, animal-dispersed seeds, and late-successional seeds showed an increase with increasing distance from forest. Even though they are exotics, fruiting guava trees may have a positive effect on forest regeneration and might prove valuable for management plans concerning forest restoration.
Variation at both the patch and landscape scale is known to influence the distribution and abundance of arboreal monkeys in rainforest fragments. However, few studies have examined the factors associated with these different scales of focus simultaneously. Using stepwise logistic-regression and generalized linear models (GLMs), howler monkey Alouatta palliata distribution and abundance were examined as a function of patch quality (fragment area, shape, tree DBH and canopy height) and landscape connectivity (isolation, total forest area, fragment and road abundance, corridor abundance and length) in 119 rainforest fragments in northern Chiapas, Mexico. The positive correlation observed between monkey distribution (presence/absence) and both fragment area and abundance may be explained by increased resources within larger fragments and those whose proximity allows greater exploration by monkeys. In contrast, GLM analysis indicated that monkey abundance in inhabited fragments was positively correlated with corridor abundance, canopy height and fragment area. These relationships could be explained by greater reproductive investments by monkeys in forest fragments whose size, degree of perturbation and degree of connectivity with other fragments suggest greater overall resource availability. Future studies should explicitly include a multi-scale approach to understanding the factors affecting patterns of monkey distribution and abundance, particularly as this relates to measures of and interactions between patch connectivity and resource availability.
a b s t r a c t Studies of plant-frugivore interactions are important for identifying the roles that biotic seed vectors play in seed dispersal, and ultimately plant recruitment. In a subandean shrubland of central Chile, 50% of total flora (14 species) has fleshy fruits dispersed by birds. We examined two aspects of frugivore-plant interaction in this system: the structure of the seed-dispersal network, to predict the effect of hypo-thetical frugivore species loss for seed dispersal and disperser effectiveness, by analyzing whether birds contribute equally to the removal of seeds from different shrub species. We show that the seed-dispersal network is highly and significantly nested, resulting in a core of interactions among generalist verte-brates and plant species. A reduction in the populations of the three main avian generalists, Turdus falcklandii, Mimus thenca and Elaenia albiceps, would disrupt seed dispersal and natural regeneration for most woody species. Monte Carlo simulations showed that the network was robust to the random loss of frugivorous species but highly sensitive to the loss of generalist species first. Mist-net sampling of birds corroborated that most fruit removal was effected by E. albiceps and T. falcklandii, highlighting the importance of frugivore species identity on seed dispersal for the maintenance of Mediterranean shrublands.
We studied the potential role as seed disperser of the pacu fish (Piaractus mesopotamicus, Characidae) in the Pantanal of Brazil. The most important food item in the diet of the pacu in the wet season was fruits of the palm Bactris glaucescens found in the guts of 73 percent of all fishes collected (N = 70). We found a positive relationship between fish length, weight, and gape size and the number of intact seeds in their gut. Therefore, large pacus are especially important in dispersing B. glaucescens seeds within the studied system. Since the best seed dispersers are the largest fishes, which are preferred by commercial fisheries, we predict that the ongoing over fishing in freshwater ecosystems will have major impacts on the dispersal system of fish-dependent plants. We suggest that it is paramount to change the attitudes in fisheries management of fruit-eating fishes and urgent to evaluate the impact of fishing on forest regeneration.
People have hunted mammals in tropical Asian forests for at least 40,000 yr. This period has seen one confirmed global extinction (the giant pangolin, Manis palaeojavanica) and range restrictions for several large mammals, but there is no strong evidence for unsustainable hunting pressure until the last 2000–3000 yr, when elephants, rhinoceroses, and several other species were progressively eliminated from the large parts of their ranges. Regional declines in most species have occurred largely within the last 50 yr. Recent subsistence hunting has typically focused on pigs and deer (hunted with dogs and spears or with snares), monkeys and other arboreal mammals (often caught with blowpipes), and porcupines and other rodents (smoked or dug out of burrows). Over the last 50 yr, the importance of hunting for subsistence has been increasingly outweighed by hunting for the market. The hunted biomass is dominated by the same species as before, sold mostly for local consumption, but numerous additional species are targeted for the colossal regional trade in wild animals and their parts for food, medicines, raw materials, and pets. Many populations of mammalian dispersers of large seeds and understory browsers have been depleted or eliminated, while seed predators have had a more variable fate. Most of this hunting is now illegal, but the law enforcement is generally weak. However, examples of successful enforcement show that hunting impacts can be greatly reduced where there is sufficient political will. Ending the trade in wild animals and their parts should have the highest regional conservation priority.
Identifying the factors that influence the extinction risk of animals is essential in conservation biology because they help identify endangered species and provide the basis for their preservation.We present a
comparative study that uses data from the literature on the diet and morphological specialization of European and North American bat species to investigate the effect of specialization on extinction risk. We focused on bats because many species are endangered and their high ecological diversity makes them a good model system for our purpose. After correcting for phylogenetic inertia, we compared the influence of dietary niche breadth as a measure of food specialization and of wing morphology as a measure of foraging strategy, habitat adaptation, and migratory ability on the vulnerability of 35 insectivorous bat species. Our results do not support the hypothesis that a narrow dietary niche breadth is related to high extinction risk. Instead they suggest that habitat specialization, which is reflected in wing morphology, influences the extinction risk of bats. Our study shows that an initial risk assessment in temperate-zone bats could be based on data of wing morphology but not on dietary data obtained from fecal analyses.
The dependency of highly endemic island floras on few potential pollinators in depauperate island faunas suggests that pollinators and seed dispersers may be crucial in the preservation of biodiversity in isolated oceanic islands. We discuss the hypothesis that flying foxes are “strong interactors” in South Pacific islands where they serve as the principal pollinators and seed dispersers, This suggests that the ongoing decline and ultimate extinction of flying fox species on Pacific islands may lead to a cascade of linked plant extinctions. We propose an empirical test of this hypothesis: comparisons of plant reproductive success in Guam, which has virtually lost its flying fox populations, and Samoa, where significant populations remain.
Resumen: La dependencia de floras isleñas altamente endemicas en algunos polinizadores potenciales en faunas islenas depauperizadas sugiere que los polinizadores y los dispersadores de semillas pueden ser cruciales en la conservacion de la diversidad biologica en islas oceanicas aisladas. Discutimos la hipotesis de que los murcielagos fnugiwros (Pteropus sp.) son fuertes interactores en las islas del Pacifico sur, en donde funcionan como los principales agentes de polinizacion y de disperseón de semillas Esto sugiere que la continua disminucion y futura extinción de las especies de murciélagos frugivoros podrian llevara una extinción de plantas en cadena. Hemos propuesto una prueba empirica de esta hipótesis, mediante la comparación del éxito reproductivo de lasplantas en Guam, que prácticamente ha perdido sus poblaciones de murciélagos frugiwros, con el de Samoa, donde persisten poblaciones impmtantes.
Valladares and Gianoli (2007) tried to answer a key question, “how much ecology do we need to know to restore Mediterranean ecosystems?” by focusing on (1) plant–plant interactions; (2) environmental heterogeneity and the potential adaptation of transplanted plants; and (3) phenotypic plasticity of the planted species. We consider their choice of topics incomplete and potentially misleading because (1) it is clearly biased toward a narrow set of research topics (phenotypic plasticity, facilitation, and climate change); (2) it assumes that active restoration, and specifically revegetation, is needed; and (3) it conveys a false perception that other basic ecological aspects of Mediterranean ecosystems are sufficiently known. Instead, we review the current knowledge on seed dispersal, succession, and ecosystem functioning for Mediterranean ecosystems. We argue that decades of research on these topics have yielded few practical guidelines for restoration, something that needs to be urgently corrected. First, the current “establishment limitation paradigm” for plant recruitment does not acknowledge the role of dispersal limitation at large spatial scales. More attention should be paid to nucleation processes and directed seed dispersal mediated by animals. Second, studies of vegetation dynamics and succession in the Mediterranean have led to an overly simplistic view of successional dynamics. How fast and deterministic succession is remains mostly unexplored; long-term monitoring of successional dynamics at different spatial scales is urgently needed. Third, information on the functional status of Mediterranean ecosystems is required to identify processes hindering natural recovery after disturbances and to set priorities on the areas and ecosystem components to be restored.
We evaluated the hypothesis that poachers reduce the abundance of herbivorous mammals, and that this, in turn, alters seed dispersal, seed predation, and seedling recruitment for two palms (Attalea butyraceae and Astrocaryum standleyanum) in central Panama. Using physical evidence left by poachers and interviews with forest guards, we quantified poaching intensity for eight forest sites. We quantified mammal abundance using transect counts and small-mammal traps. Abundance was inversely related to poaching intensity for 9 of 11 mammal species (significantly so for 5 species), confirming the first component of the hypothesis. The outcome of interactions among seeds, mammals, and beetles also varied with poaching intensity. Nonvolant mammals were the only seed-dispersal agents, and rodents and beetles were the only seed predators. We quantified seed fate by examining the stony endocarps that encase the seeds of both palms. The large, durable endocarps were located easily on the forest floor and bear characteristic scars when a rodent or beetle eats the enclosed seed. The proportion of seeds dispersed away from beneath fruiting conspecifics was inversely related to poaching intensity, ranging from 85% to 99% at protected sites where mammals were abundant and from 3% to 40% at unprotected sites where poachers were most active. The proportion of dispersed seeds destroyed by beetles was directly related to poaching intensity, ranging from 0% to 10% at protected sites and from 30% to 50% at unprotected sites. The proportion of dispersed seeds destroyed by rodents was inversely related to poaching intensity, ranging from 85% to 99% at protected sites and from 4% to 50% at unprotected sites. Finally, seedling densities were directly related to poaching intensity. There was no single relationship between poaching intensity and the biotic interactions that determine seedling recruitment. The net effect of poaching on seedling recruitment can be determined only empirically. For these palms, seedling densities were directly related to poaching intensity.Resumen: Evaluamos la hipótesis que los cazadores reducen la abundancia de mamíferos herbívoros y que esto, a su vez, altera la dispersión de semillas, la depredación de semillas y el reclutamiento de plántulas de dos palmeras (Attalea butyraceae y Astrocaryum standleyanum) en Panamá central. La intensidad de cacería fue cuantificada para ocho sitios dentro de bosque, utilizando la evidencia física dejada por los cazadores y entrevistas con los guardaparques. La abundancia de mamíferos fue cuantificada usando conteos a lo largo de transectos y trampas para los mamíferos pequeños. La abundancia estuvo inversamente relacionada a la intensidad de cacería para nueve de 11 especies de mamíferos (significativamente en cinco especies), confirmando el primer componente de la hipótesis. El resultado de las interacciones entre semillas, mamíferos y escarabajos, también varió con la intensidad de cacería. La suerte de las semillas fue cuantificada utilizando el endocarpo duro que recubre a las semillas de ambas palmeras. Estos endocarpos grandes y durables son fácilmente encontrados sobre el suelo del bosque, y tienen cicatrices características cuando un roedor o escarabajo comió la semilla dentro de éste. Los mamíferos no voladores son los únicos agentes que dispersan estas semillas, y los roedores y escarabajos son los únicos depredadores de las mismas. La proporción de las semillas dispersadas, lejos de abajo de los coespecíficos en fructificación, estuvo inversamente relacionada a la intensidad de cacería (dentro de un rango desde 85% hasta 99% en los sitios protegidos donde los mamíferos eran abundantes, y desde 3% hasta 40% en los sitios desprotegidos donde los cazadores estaban más activos). La proporción de semillas dispersadas exterminadas por escarabajos estuvo directamente relacionada a la intensidad de cacería (dentro de un rango desde 0% hasta 10% en los sitios protegidos, y desde 30% hasta 50% en los sitios desprotegidos). La proporción de semillas dispersadas exterminadas por roedores estuvo inversamente relacionada a la intensidad de cacería (dentro de un rango desde 85% hasta 99% en los sitios protegidos, y desde 4% hasta 50% en los sitios desprotegidos). Finalmente, las densidades de plántulas estuvieron directamente relacionadas a la intensidad de cacería. No se encontró una relación única entre la intensidad de cacería y las interacciones bióticas que determinan el reclutamiento de plántulas. El efecto neto de la cacería sobre el reclutamiento de plántulas solamente puede ser determinado empíricamente.
In this paper, I analyse the interaction between the holm-oak Quercus ilex, and one of its main dispersers, the European jay Garrulus glandarius, in an heterogeneous Mediterranean landscape. I quantify the spatial dispersal pattern of the seed shadow at two spatial scales, landscape (among patches) and microhabitat (within patches), by directly tracking the movement of seeds. Two main traits of the jay-mediated dispersal of holm-oak acorns across the landscape, the spatial pattern of dissemination and the distance from the source tree, are significantly and directly influenced by jay activity. Jays moved acorns nonrandomly, avoiding one main patch type of the study area to cache acorns, the shrubland-grasslands, and moving most of the acorns to pine stands, whether afforestation or open pinewoods. Within each patch type, jays had also a strong preference for caching acorns in some microhabitats, since>95% of the acorns dispersed by jays were cached beneath pines. The distance of holm-oak acorn dispersal was long in the study site, over 250 m, with some dispersals occurring up to 1 km from the source oaks. The shape of the dispersal kernel function fitted to the dispersal pattern produced by jays differed from those quantified for many other plant species. Jay-mediated dispersal had two components, one local and another produced by long-distance dispersal. Due to the heterogeneity of these Mediterranean environments, this difference in scale overlaps with a difference in habitat composition, short distances events resulting in dispersals within the same oak stands and long distance events resulting in dispersal outside of oak stands, usually to other vegetation units. Jay activity and movement pattern can have thus dramatic effects on both the local regeneration as well as the potential for regional spread of the holm-oak populations.
An ability to predict species’ sensitivities to habitat loss and fragmentation has important conservation implications, and numerous hypotheses have been proposed to explain interspecific differences observed in human-dominated landscapes. We used occupancy data collected on 32 species of vertebrates (16 mammals and 16 amphibians) in an agricultural landscape of Indiana, USA, to compare hypotheses that focus on different causal mechanisms underlying interspecific variation in responses to habitat alteration: (1) body size; (2) morphology and development; (3) behaviour; (4) niche breadth; (5) proximity to range boundary; and multiple-process models combining main effects and interactions of hypotheses (1)–(2) and (4)–(5). The majority of habitat alteration occurred over a century ago and coincided with extinction of several species; thus, our study dealt only with variation in responses of extant species that often are considered ‘resistant’ to human modifications of native habitat. Corrected Akaike scores and Akaike weights provided strongest support for models incorporating niche breadth and proximity to range boundary. Measures of dietary and habitat breadth obtained from the literature were negatively correlated with sensitivity to habitat alteration. Additionally, greater sensitivity was observed for species occurring at the periphery of their geographical ranges, especially at northern or western margins. Body size, morphological, developmental and behavioural traits were inferior predictors of tolerance to fragmentation for the species and landscape we examined. Our findings reinforce the importance of niche breadth as a predictor of species’ responses to habitat alteration. They also highlight the importance of viewing the effects of habitat loss and fragmentation in a landscape within a biogeographical context that considers a species’ level of adaptation to local environmental conditions.
The introduction of exotic species to an island can have significant effects on the population density and distribution of native species and on the ecological and evolutionary interactions among them (e.g., plant-animal mutualisms). The disruption of these interactions can be dramatic, significantly reducing the reproductive success of the species and even leading to their extinction. On Menorca Island (Balearic Islands, western Mediterranean), we examined the consequences of the disruption of the mutualism between two endemic species: a perennial shrub, ( Daphne rodriguezii [Texidor]) and a frugivorous lizard (Podarcis lilfordi [Günther]). The lizard became extinct from this island (as well as from Mallorca) as a result of the introduction of carnivorous mammals, which has continued since Roman times. The relict mutualism between D. rodriguezii and the lizard currently persists only in an islet (60 ha) where P. lilfordi is still abundant. We hypothesized that the absence of this lizard from most Menorcan populations is the factor causing the regression of this plant, currently considered at risk of extinction. Through observation and experimentation in the field and laboratory, we found strong evidence that a lack of seed dispersal in Menorca is the main cause of the low seedling recruitment. First, the population with greatest seedling recruitment was that in the islet where lizards were abundant. Second, lizards appeared to be the only dispersers of D. rodriguezii. Lizards consumed large amounts of fruits, without affecting either germination or seedling growth, and moved seeds to sites suitable for plant establishment. Seedlings in Menorca, in contrast, recruited almost exclusively under the parent plants. Third, the effect of other factors that may influence plant population growth (a low fruit set and a high postdispersal seed predation) was similar between the islet and the Menorcan populations. To our knowledge, our results are the first that quantitatively show that a biological invasion can cause a disruption of a specialized plant-vertebrate mutualism that sets the plant partner on the road to extinction.
Resumen: La introducción de especies exóticas a una isla puede tener efectos significativos sobre la densidad y distribución de especies nativas y sobre sus interacciones ecológicas y evolutivas (e.g. mutualismos planta-animal). La alteración de estos mutualismos puede ser dramática, altera significativamente el éxito reproductivo y puede provocar la extinción de las especies. Examinamos las consecuencias de la interrupción del mutualismo en dos especies endémicas en la isla Menorca (Islas Baleares, Mediterráneo occidental): un arbusto perenne, ( Daphne rodriguezii [Texidor]) y una lagartija frugívora ( Podarcis lilfordi [Günther]). La lagartija se extinguió en esta isla (así como en Mallorca) debido a la introducción de mamíferos carnívoros desde tiempos Romanos. Actualmente, el mutualismo relicto entre Daphne rodriguezii y la lagartija solo persiste en un islote (60 ha), donde P. lilfordi aún es abundante. Probamos la hipótesis que la ausencia de esta lagartija en la mayoría de las poblaciones de Menorca es lo que está causando la regresión de esta planta, actualmente considerada en riesgo de extinción. Mediante observación y experimentación en el campo y laboratorio, encontramos fuerte evidencia de que la falta de dispersión de semillas en Menorca es la principal causa del bajo reclutamiento de plántulas. Primero, porque la población con el mayor reclutamiento de plántulas fue la del islote, donde la lagartija abunda. Segundo, parece que las lagartijas son el único dispersor de D. rodriguezii. Las lagartijas consumieron grandes cantidades de frutos, sin afectar a la germinación ni al crecimiento de plántulas, y movieron semillas a sitios adecuados para el establecimiento de plántulas. En contraste, plántulas en Menorca reclutaron casi exclusivamente debajo de las plantas parentales. Tercero, el efecto de otros factores que pueden influenciar al crecimiento de la población de plantas (baja de frutos y alta depredación de semillas post dispersión) fueron similares entre el islote y las poblaciones de Menorca. Hasta donde sabemos, nuestros resultados son los primeros que muestran cuantitativamente que una invasión biológica puede provocar la interrupción de un mutualismo planta-vertebrado especializado que coloca a la planta asociada en el camino a la extinción.
Disperser effectiveness is the contribution a disperser makes to the future reproduction of a plant. Although it is a key notion in studies of seed dispersal by animals, we know little about what determines the effectiveness of a disperser. The role of the present paper is to review the available information and construct a hierarchical framework for viewing the components of disperser effectiveness.Effectiveness has both quantitative and qualitative components. The quantity of seed dispersal depends on (A) the number of visits made to the plant by a disperser and (B) the number of seeds dispersed per visit. The quality of seed dispersal depends on (A) the quality of treatment given a seed in the mouth and in the gut and (B) the quality of seed deposition as determined by the probability that a deposited seed will survive and become an adult. In this paper I review the ways disperser behavior, morphology and physiology can influence these major components of disperser effectiveness, and when data permit present preliminary analyses of relationships among components.
Clearance, fragmentation, and degradation of tropical forests have resulted in declines of biodiversity. This loss of biodiversity is endangering important ecosystem processes such as seed dispersal. If anthropogenic disturbances affect seed dispersal of keystone plants, effects on tropical ecosystems might be especially pronounced. We studied frugivore assemblages and fruit removal from 25 Ficus thonningii trees in the heavily fragmented and disturbed Kakamega Forest, western Kenya. During 400 observation hours we recorded 36 frugivores visiting F. thonningii trees. We recorded significantly fewer frugivorous species in fragments compared to the main forest and in highly, compared to little, disturbed sites. Effects of fragmentation and local disturbance on the number of individuals were not significant but showed similar trends to those in the previous analyses. Furthermore, fruit removal from focal trees was slightly reduced in fragmented and significantly reduced in highly disturbed sites. These results suggest that mutualistic interactions of keystone species can be particularly sensitive to human forest disturbance with potential long-term effects on the biodiversity of tropical forests.
Population declines of farmland birds over recent decades in Europe, Canada and the USA have been attributed to more intensive agricultural management. We counted birds during the 1990 breeding season on 72 field sites in southern Ontario, Canada, paired between 10 organic and 10 conventional farms for local habitat to enhance our ability to detect effects of agricultural practices. Of 68 species recorded, 58 were on organic sites, 59 on conventional. Species richness and total abundance were significantly greater on organic than conventional sites based on log-linear regression. Of 43 species analyzed with log-linear regression, eight (18.6%) were significantly (P<0.05) more abundant on organic than conventional sites and four (9.3%) approached significance (0.05<P<0.10). Eight of these 12 species had negative population trends for 1967–1998 Breeding Bird Surveys (BBS) in this region. Two of the 43 species analyzed (4.7%) were significantly more abundant on conventional than organic sites and three (7.0%) approached significance. Two of these five species had negative BBS population trends. A canonical correspondence analysis (CCA) of 13 practices and 13 habitat variables explained 44% of total variation (TV) accounted for in a detrended correspondence analysis of bird species composition and abundance. Practices contributed 23.7% of TV, habitat 26%; habitat and practices shared 5.7% with each other and 12% with farm ownership (i.e. clustering of field sites within farms). CCA ordinations indicated considerable mixing of organic and conventional sites across a gradient from sites with many birds species associated with greater habitat heterogeneity and more pasture, winter grain, farmstead and other non-crop habitats (hedgerow, woodland) to sites with few bird species associated with larger fields, more rowcrop and spring grain, more passes and tilling, and use of herbicides and chemical fertilizers. Our results re-emphasize the importance of non-crop habitats, more permanent crop cover, and less intensive management practices to the conservation of avian biodiversity on farmland.
Humans hunt forest vertebrates throughout the tropics. Many preferred game species consume flowers, fruit, seeds and/or leaves, and these interactions will cause their harvest to ramify through forests. Three related issues will determine how severely the harvest of forest vertebrates influences the plant community. First, the types of species selected by hunters and the intensity of the harvest will determine which vertebrates are removed and which remain. Second, the possible presence of ecologically similar, non-game species able to expand their activities to fulfill the ecological role of heavily exploited species will determine how severely the harvest disrupts ecological relationships between the community of forest vertebrates and the community of forest plants. Finally, hunters will alter plant species composition if the harvest of vertebrates differentially affects mutualists or pests of particular plant species. Hunters will also alter plant diversity if the harvest of vertebrates disrupts ecological mechanisms that permit plant species to coexist. I examine hunter selectivity, the intensity of the hunt, possible compensation by non-game species, and the types and strengths of interactions among game species and plants for tropical forests to determine when and where these outcomes occur.
Migratory frugivorous birds disperse the seeds of many plant species, forming mutualistic associations that render frugivores a priority for conservation in many habitats worldwide. We analysed the distribution of seed-dispersing frugivorous passerines in southern Spain, which is an important area for the conservation of European birds during winter. Frugivorous birds showed similar regional abundance and richness during four winters, although fruit availability changed among years. However, the spatial distribution of frugivorous birds in the area changed among years. These changes were principally determined by annual variation in the distribution of fruits in the area, revealing a clear ability of birds to track the distribution of fruits. The unpredictable distribution of fruits each year suggests that regional fruit crops, rather than selected habitat patches, need to be protected for the long-term conservation of frugivorous bird populations in wintering grounds. Remarkably, the distribution of frugivores was independent of forest development or general cover of shrubs, which helps to reconcile the protection of fruiting shrubs with forest cleaning, an usual management to prevent devastating summer fires that is destroying fleshy-fruited plant communities in many areas of southern Spain. Thus, leaving a part of the fruiting shrubs untouched when cleaning forest undergrowth will allow the settlement of frugivorous birds. Interestingly, both abundance and richness of frugivores decreased with elevation, probably as a consequence of impaired climatic conditions at high altitude, revealing the importance of lowland shrublands as wintering grounds for frugivorous birds. These habitats deserve special conservation efforts, as they are seriously threatened by the ongoing encroachment of agricultural and urban areas along the Mediterranean coasts.
We review whether migratory Anatidae, i.e., swans, geese and ducks, could be acting as vectors for dispersal of Zostera, Ruppia and Potamogeton propagules by endozoochory (carrying seeds in their guts). We list six prerequisites that must all be fulfilled, if successful dispersal should occur. Several Anatidae species feed on these macrophytes, and undertake rapid long-distance movements, making dispersal possible. We identify four problems, which in combination leads us to conclude that long-distance dispersal events are likely to be rare. (i) Most long-distance movements are out of phase with the reproductive efforts of the plants, and if birds arrive at sites when plants still bear seeds, they are likely to depart well after seed stocks have been depleted. (ii) Seed transport by birds will usually be uni-directional, from north to south on autumn migrations. (iii) Most of the gut contents of migratory birds are likely to have been discarded within 300 km of departure. (iv) In many cases, birds will arrive in habitats seriously different from those they departed, i.e., any seeds carried along will have low chances of surviving in their new site. We suggest that northbound dispersal by endozoochory can only occur during spring if waterbirds feed on seeds that have not been depleted and remained frozen down or buried in sediments, or during moult- or post-moult migrations. Moult migration takes place in summer in phase with the reproductive efforts of the plants. Also epizoochorous dispersal (external attachment) is subject to restrictions i, ii and iv.
This paper presents the results of a 22-month survey and the examination of the intestinal content of 356 specimens of Xenohyla truncata (Anura: Hylidae) from Restinga de Maricá, Rio de Janeiro, Brazil. Our results confirm prior observations that fruits are intrinsic to the diet of these frogs. In addition, these new data increase our understanding of the relationship between frogs and the plants they feed upon. Plant consumption follows availability of fruits in the area, indicating that the diversity of fruits consumed by the frogs does not represent choice, but rather plant phenology and fruit availability.