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Response diversity, ecosystem change, and resilience
... However, we emphasize the need for both functional diversity and functional redundancy in urban ecosystems. While functional diversity emphasizes the importance of incorporating a variety of species with distinct ecological roles into urban green spaces, enhancing ecosystem health and sustainability (Elmqvist et al., 2003), functional redundancy acknowledges the potential benefits of having multiple species performing similar functions, maintaining critical functions despite environmental changes (Laliberté et al. 2010). To support species selection based on functional groups, further research should focus on assessing tree phytosanitary status and analyzing long-term cause-effect relationships between trees and social-ecological variables, supported by accessible trait databases that include critical urban traits, such as root characteristics (Roman et al., 2021). ...
... The coexistence of different ecosystems and habitat types, and maintaining and restoring landscape connectivity are key to enhancing ecosystem resilience [48,49]. In addition, the biodiversity and structural complexity in the landscape contribute to the ecosystem's ability to adapt to environmental changes [50]. ...
Accelerated urbanization has induced multifarious disturbances and shocks in rural areas. Resilience theory is instrumental in explaining the interactions and outcomes between village systems and external environmental systems, rendering rural resilience research an emerging focus. Based on a 20-year span of relevant literature from the Web of Science database, this paper elucidates the developmental stages, principal themes, and measurement frameworks of rural resilience research, and examines the limitations and future directions of current research. The main conclusions of the study are as follows: (1) Over the past 20 years, rural resilience research has shown a continuous growth and gone through three stages of development. (2) The core topics focus on the exploration of impact mechanisms, assessment in the context of disasters, and landscape ecological planning and construction, yet unified and comprehensive analysis frameworks have been rarely reported. (3) In the future, more attention should be paid to dynamics and complexity, and the level of rural resilience should be empirically analyzed from an integrated perspective. This study provides a theoretical basis for rural development and resilience planning, emphasizing the response to uncertainty disturbances through cross-scale elemental linkages to achieve sustainable rural development. Clinical trial number: Not applicable.
... They found that different environmental indicators and vegetation indicators had different impacts on biodiversity, and the relationship between landscape diversity and stability in the forest-grassland ecotone tended to be a combination effect. In addition, Elmqvist et al. [24] and Thébault and Loreau [25] also pointed out that diverse species combinations can improve the stability of the ecosystem, and interactions between species can stimulate the adaptability and resilience of the ecosystem. Therefore, in view of the superimposed ecosystems of the forest-grassland ecotone, the evaluation of the landscape structure only from the perspective of landscape risk by using indicators such as landscape fragmentation and landscape vulnerability is still not comprehensive. ...
Forest–grassland ecotones refer to the transitional area between forest and grassland ecosystems. Previous studies mainly focus on environmentally sensitive features and landscape risk pressures caused by edge effects, ignoring the landscape restoration and stability changes brought about by high species diversity. In this study, we calculated the landscape stability in the forest–grassland ecotone of the Greater Khingan Mountains in Inner Mongolia, China from 1990 to 2020, analyzed the changing trends and spatial migration dynamics of the landscape stability, and revealed the potential driving factors and spatial heterogeneity of dominant driving factors for the changes in landscape stability. The results indicated that the dominant landscapes in the study area changed from forests and grasslands in 1990 to forest-dominated landscapes in 2020, and the landscape stability gradually improved from a lower level to a higher level. The stability gradually expanded from the center to the northeast and southwest edges, exhibiting a ribbon sprawl pattern, and the stable center gradually moved to the northeast from 1990 to 2020. Climate factors were the main driving forces affecting the changes in landscape stability in the study area. Different dominant driving factors showed various spatial heterogeneity over time. In the northern part of the forest–grassland ecotone, precipitation, and NDVI had positive correlations with landscape stability, while the opposite was true in the south. In addition, the area of landscape stability in the south that was positively correlated with temperature and NDVI gradually expanded over time. This study analyzed the unique ecological advantages of the forest–grassland ecotones from the perspective of landscape stability changes, which will be facilitated in the ecological assessments and restoration of the forest–grassland ecotones.
... • Diversity: the range of reactions and opportunities within an ecosystem that enables adaption, renewal, and persistence during disturbance and change (Elmqvist et al. 2003;Standish et al. 2014). When diversity is high, it is more likely the conditions, traits, or information needed to adapt to disturbances are available. ...
Clear limits for cumulative effects are needed to safeguard the ecological structures, functions, and processes on which society depends in a rapidly changing world. However, ecological thresholds are difficult to discern and even more challenging to integrate meaningfully into cumulative effects assessments (CEA). It has been suggested that establishing a safe operating space for cumulative effects could move the dial forward in this respect. Yet, there remains little guidance on how to achieve this. Here, we propose a schema for measuring cumulative effects relative to a safe operating space grounded in ecological resilience. We then explore practical considerations for implementing this schema in CEA based on six attributes of a resilient ecosystem: diversity, connectivity, modularity, memory, openness, and feedbacks. We posit that a safe operating space may serve as a powerful tool to understand how our collective footprint may be undermining the ability of ecosystems to adapt and respond to future disturbances. By assessing cumulative effects against a safe operating space, society can better understand when systems are pushed to the edge of their safe zone and manage our interactions so as to avoid a catastrophic shift in the conditions needed for ecological and societal prosperity.
... Most studies still concentrate on a single factor, and only a few have noticed the combined influence of multiple factors [38,57]. In contrast, a large number of phenomena in nature are caused by the complex synergy of the latter condition [58,59], including "ecological surprises" such as drastic shifts in community compositions and biodiversity [38,60,61]. ...
... Here, we expect that EC may be acting as a stressor reducing the richness and abundance of microbes within groundwater (Elmajdoub et al. 2014). Both microbial activity and richness are fundamentally linked to ecosystem resilience (Elmqvist et al. 2003) and stress responses (Wang et al. 2011), and both were affected by high EC in this study. A decrease in community resilience can affect the provision of ecosystem services and functions (Walker 1992;Oliver et al. 2015) and, in groundwaters, this may be evident as a decline in the microbial functions that maintain water quality (Chapelle 2000). ...
Context
Understanding the impacts of salinity on groundwater microbial communities is imperative, because these communities influence groundwater chemistry, quality, and its suitability for use by humans and the environment.
Aim
To assess groundwater salinisation and its influence on groundwater microbial communities within the Murray–Darling Basin (MDB), Australia.
Methods
Alluvial aquifers were sampled from 41 bores, within the Lachlan, Murrumbidgee and Murray catchments. Environmental DNA (eDNA), microbial activity and water-quality variables were measured to evaluate microbial communities, which were then correlated with electrical conductivity (EC) and other environmental variables.
Results
Our results indicated widespread groundwater salinisation within the MDB, with EC ranging from 63 to 51 257 μS cm⁻¹. The highest EC values were recorded in the Murray catchment; however, mean EC values did not differ significantly among catchments (P > 0.05). The composition of microbial communities differed significantly between sites with low (<3000 μS cm⁻¹) and high (>3000 μS cm⁻¹) EC. Microbial activity, richness and abundances were all greater at low- than high-EC sites.
Conclusions
Changes to microbial communities as demonstrated here may have impacts on biogeochemical cycling and ecosystem resilience.
Implications
The detrimental ecological impacts of salinity are not limited to groundwater microbes, but present a larger ecological issue affecting all groundwater-dependent ecosystems.
... The increasing loss in the genetic variation in the tilapia may decrease its potential to overcome the habitat degradation due to anthropogenic activities. Ecosystem has complete dependence upon their diversity inside [18]. Interaction among number of species of habitat in an aquatic ecosystem may direct to uphold composition structure of fish fauna [19]. ...
Cirrhinus mrigala (Family Cyprinidae) have vast presence in different studied rivers of Pakistan. Present study was designed to formulate the genetic diversity of desired sites in Cirrhinus mrigala populations using nine Random amplified polymorphic DNA markers. Total hundred individuals were used to conduct this study and were collected from three distinct rivers (River Indus, Chenab and Ravi) with four specified sites with wild of Pakistan were used to study. A random Amplified Polymorphic DNA primer analyzes various bands of polymorphic loci. Mean genetic diversity within and between populations found 81.53% and 2.27% respectively by using analysis of molecular variance. Fixation index was found variably and Pairwise F st analysis showed significant difference between different sites of studied populations. Genetic divergence information would mark Original Research Article Naeem et al.; ARRB, 35(7): 1-9, 2020; Article no.ARRB.56666 2 essential in order to improve genetic programming its management and conservation of natural inhabitation. In order to quantify the study of population divergence by using these molecular markers is an efficient way to pin point the genetic diversity within and among population.
... diversity-stability relationship; Ives & Carpenter, 2007;Tilman et al., 1996). Given that a speciose community should exhibit greater response diversity-the range of species' responses to an environmental change (Elmqvist et al., 2003)-diverse communities on average should have a higher probability of maintaining critical functions under stress (i.e. biological insurance theory; Yachi & Loreau, 1999). ...
Climate change is causing marked shifts to historic environmental regimes, including increases in precipitation events (droughts and highly wet periods). Relative to droughts, the impacts of wet events have received less attention, despite heavy rainfall events increasing over the past century. Further, impacts of wet and dry events are often evaluated independently; yet, to persist and maintain their ecosystem functions, plant communities must be resilient to both precipitation events. This is particularly critical because while community properties can modulate the resilience (resistance, recovery, and invariability) of ecosystem functions to precipitation events, community properties can also respond to precipitation events. As a result, community responses to wet and dry years may impact the community's resilience to future events.
Using two decades (2000–2020) of annual net primary productivity data from early successional grassland communities, we evaluated the plant community properties regulating primary productivity resistance and recovery to contrasting precipitation events and invariability (i.e. long‐term stability). We then explored how resilience‐modulating community properties responded to precipitation.
We found that community properties—specifically, evenness, dominant species (Solidago altissima) relative abundance, and species richness—strongly regulate productivity resistance to drought and predict productivity invariability and tended to promote resistance to wet years. These community properties also responded to both wet and dry precipitation extremes and exhibited lagged responses that lasted into the next growing season. We infer that these connections between precipitation events, community properties, and resilience may lead to feedbacks impacting a plant community's resilience to subsequent precipitation events.
Synthesis. By exploring the impacts of both drought and wet extremes, our work uncovers how precipitation events, which may not necessarily impact productivity directly, could still cryptically influence resilience via shifts in resilience‐promoting properties of the plant community. We conclude that these precipitation event‐driven community shifts may feedback to impact long‐term productivity resilience under climate change.
... A wider range of functional types in the encroaching woody plant community likely means there will be higher 'response diversity' if conditions change in a way that would harm the currently dominant woody species (i.e. Elmqvist et al., 2003;Loreau et al., 2021). Ultimately, the diversity of encroaching woody species in mesic grasslands may make it more challenging to reach management goals that aim to combat encroachment and restore encroached grasslands. ...
Changes in climate and land management over the last half‐century have favoured woody plants native to grasslands and led to the rapid expansion of woody species. Despite this being a global phenomenon, it is unclear why some woody species have rapidly expanded while others have not. We assessed whether the most abundant woody encroaching species in tallgrass prairie have common growth forms and physiology or unique traits that differentiate their resource‐use strategies.
We characterized the abundance, above‐ground carbon allocation, and leaf‐level physiological and structural traits of seven woody encroaching species in tallgrass prairie that span an order of magnitude in abundance. To identify species‐specific increases in abundance, we used a 34‐year species composition dataset at Konza Prairie Biological Station (Central Great Plains, USA). We then compared biomass allocation and leaf‐level traits to determine differences in carbon and water use strategies among species.
While all focal species increased in abundance over time, encroachment in this system is primarily driven by three species: Cornus drummondii, Prunus americana and Rhus glabra. The most dominant species, Cornus drummondii, had the most extreme values for several traits, including the lowest leaf:stem mass ratios, lowest photosynthetic capacity and highest turgor loss point.
Two of the most abundant species, Cornus drummondii and Rhus glabra, had opposing growth forms and resource‐use strategies. These species had significantly different above‐ground carbon allocation, leaf‐level drought tolerance and photosynthetic capacity. There were surprisingly few interspecific differences in specific leaf area and leaf dry matter content, suggesting these traits were poor predictors of species‐level encroachment.
Synthesis. Woody encroaching species in tallgrass prairie encompass a spectrum of growth forms and leaf physiology. Two of the most abundant woody species fell at opposite ends of this spectrum. Our results suggest niche differences among a community of woody species facilitate the rapid encroachment by a few species. This study shows that woody encroaching species do not conform to a ‘one‐size‐fits‐all’ strategy, and a diversity of growth forms and physiological strategies may make it more challenging to reach management goals that aim to conserve or restore grassland communities.
... The thematic synthesis favors a cross-disciplinary positioning of resilience more broadly as (1) a dynamic process or response that (2) results in a change that is (3) ultimately in some way positive for the entity undergoing change. This contrasts definitions that prefer to categorize resilience only as the state before a fundamental change [96] or the return to a pre-disturbance state [97] and aligns with those that position it as inclusive of process and progress [1,6] (p. 1670), [98] ...
Resilience has become a focal point of academic research investigating the impact of adverse disruption to the well-being of people, systems, the built environment, ecosystems, and climate. However, the proliferation of this work has not been accompanied by increasing clarity about the core meaning of resilience as a singular construct, threatening its relevance and complicating its use in practice. To improve the application of resilience in cross-disciplinary and convergence approaches to sustainability and well-being research, this work synthesized resilience conceptualizations across disciplines with novel artificial intelligence (AI)-augmented approaches. Using open-source applications for text mining and machine-learning-based natural language processing algorithms for the examination of text-as-data, this work mapped the content of 50 years of academic resilience work (24,732 abstracts). Presented as thematic and statistical textual associations in a series of network maps and tables, the findings highlight how specific measurements, components, and terminologies of resilience relate to one another within and across disciplines, emphasizing what concepts can be used to bridge disciplinary boundaries. From this, a converged conceptualization is derived to answer theoretical questions about the nature of resilience and define it as a dynamic process of control through the stages of disruption and progression to an improved state thereafter. This conceptualization supports a cross-disciplinary meaning of resilience that can enhance its shared understanding among a variety of stakeholders, and ultimately, the rigor and uniformity of its application in addressing sustainability and well-being challenges across multiple domains.
... In cases where keystone species that form a crucial role in the food web disappear or re-appear, it could have cascading effects on the entire community (Estes et al., 2011;Hughes et al., 2024). Also reduced diversity per se is supposed to reduce the resistance of ecosystems to withstand various stressors, as well as the resilience to restore the system after disturbance (Elmqvist et al. 2003;Ives & Carpenter, 2007;Oliver et al., 2015). ...
Globally, locally, and regionally, there are different patterns of biotic diversity and community composition reflecting past evolutionary history shaped by differences in niches, productivity, climate, and other ambient factors, as well as migration barriers. Historically, humans have impacted and eroded these biotic patterns, notably by the impact of agriculture in a wide sense, but to an increasing extent also by logging, overharvesting, spreading of species, urbanization, and climate change. Besides causing (in most cases) a declining diversity, it also implies a biotic homogenization where ecosystem communities become spatially more similar, often by replacement of locally adopted specialist species with more widespread generalist species. Besides discussing these drivers of biotic degradation and homogenization, I also discuss why and how it matters both from a biocentric and anthropocentric point of view, how biotic and cultural homogenization are integrated via agricultural impacts, loss of habitats that also are home to indigenous people as well as by travel, trade, and consumption. In fact, the global cultural homogenization towards western consumerism is the overarching cause of biotic homogenization, biodiversity loss as well as climate change. Finally, solutions are discussed. There are local and regional means to counteract biotic losses and homogenization by retaining and restoring landscape elements, yet globally these trends can only be countered through systemic societal changes.
... Another advantage of non-bees is that they may be less sensitive than bees to changes in land use (Rader et al., 2016). If non-bees and bees pollinate the same crops, increased 'response diversity' may lead to stabilization of pollination performance (Elmqvist et al., 2003;Schmack & Egerer, 2023). Furthermore, visitation by diverse wild bees and non-bees promotes fruit and seed set of crops more than increased visitation by honey bees (Rader et al., 2016). ...
Insect decline and loss of biodiversity not only affect large‐scale agricultural landscapes, but are increasingly recognized in urban environments. It is undisputed that a greater supply of flowers in urban green spaces can provide insects with more food and habitat. However, it is still controversial whether native wild plants or non‐native ornamental plants and varieties are the right choice.
To answer this question we investigated the number of insects interacting with different types of plants: twelve ornamental and six related wild perennials. In this context, the number of flower visitors per plant species and plot was recorded at 10‐minute observation intervals, as well as the feeding damage caused by insect herbivores on the leaves and stems of the study plants. We established 18 plant species in ten independent study plots in the city of Darmstadt, Germany. The plants were six native wild plant species, six ornamental plant species related to the wild plants from the same genus or family and six exotic ornamental plant species from other genera and families than the wild plants.
Native insects (wild bees, flies, beetles, wasps) that feed on pollen and nectar visited wild perennials significantly more often (67% of all visits) than related ornamental (24%) and unrelated exotic plants (9%). In contrast, honey bees (Apis mellifera) showed no preferences to any of the three target plant groups and interacted with other plant species than most of the native insects in our study according to analyses of interaction networks.
The assessment of leaf damage caused by insect herbivores on the individual plants confirmed a similar and significant difference in the insects' choices. Leaves from wild plants showed the highest herbivory (mean 2.3% of the leaf area), followed by related ornamental plants (0.8%), whereas unrelated exotic plants were hardly consumed (0.1%) by herbivores.
Practical implication. Our study shows that in urban green spaces, both flower‐visiting and leaf‐feeding insects are more likely to use native wild plants as a food source than closely related and exotic ornamental plants.
... Income might be a relatively new factor, emerging later in a household's tenure, while decisions about plant diversity in gardens may be shaped over years. Furthermore, the negative effect of tenancy arrangements on both diversity indexes supports the idea that ownership and investment in property contribute to higher biodiversity in urban settings (Elmqvist et al. 2003;Andersson et al. 2007;Aronson et al. 2017). Thus, the security and sense of ownership associated with private home ownership may contribute to a greater investment in cultivated plant diversity within urban settings. ...
Urbanization is a driving factor for biodiversity loss and potential climate change by reducing carbon stocks. Understanding how urban development, as mitigated by socio-economic factors alters urban biodiversity is crucial for effective urban planning that maintains or improves environmental resilience. The luxury effect hypothesis predicts that wealthier parts of a city will have higher levels of biodiversity. This effect has been tested widely but we still have limited understanding of how wealth influences urban biodiversity in tropical regions of developing countries where plant species play profound sociocultural roles beyond aesthetics. This study investigates links between household income and the diversity of cultivated plants distribution within neighborhoods of two growing cities in Benin. We conducted a survey of 936 randomly selected households to record their socioeconomic characteristics and survey the cultivated plant species found in household gardens’. This enabled us to estimate household-level diversity metrics including taxonomic diversity and phylogenetic diversity. We found no global support for the luxury effect on phylogenetic diversity but rented properties had lower plant taxonomic diversity along with less phylogenetic diversity than privately owned houses. Taxonomic diversity is higher in the less urbanized areas while phylogenetic diversity is weakened. Household’s cultural connection to plants has a negative effect on both diversity indices. Our results highlight the complex relationships between socioeconomic traits and urban plant diversity distribution in two tropical African cities, which only partly confirmed the luxury effect hypothesis. Disentangling these complex relationships can help city planners and policymakers to take informed decisions to promote sustainable cities.
... Mutualistic interaction network resilience (hereafter: network resilience) is important as it sustains the smooth flow of ecosystem services in different and rapidly changing environments. However, as anthropogenic activities continuously modify the ability of ecosystems to buffer perturbations, this would eventually lead to a reduction in essential ecosystem services crucial for our well-being (Elmqvist et al., 2003). Over the last two decades, studies that aimed at addressing the network resilience of mutualistic interactions have been mainly based on meta-analyses and numerical simulations such as minimalist process-based and stochastic modelling (Huang and D'Odorico, 2020;Schleuning et al., 2016;Vieira and Almeida-Neto, 2015) of aquatic (Elliott, 2010) and terrestrial ecosystems (Dakos and Bascompte, 2014). ...
Interaction network resilience can be defined as the ability of interacting organisms to maintain their functions, processes or populations after experiencing a disturbance. Studies on mutualistic interactions between plants and pollinators along environmental gradients are essential to understand the provision of ecosystem services and the mechanisms challenging their network resilience. However, it remains unknown to what level ecological changes along climatic gradients constrain the network resilience of mutualistic organisms, especially along elevation gradients. We surveyed bee species and recorded their interactions with plants throughout the four major seasons (i.e. long and short rainy, and long and short dry) on 50 study sites positioned along an elevation gradient (525 m to 2,530 m asl) in the Eastern Afromontane Biodiversity Hotspots in Kenya, East Africa. We calculated bee and plant network resilience using the network resilience parameter (β eff) and assessed changes in bee and plant network resilience along the elevation gradient using generalised additive models (gams). We quantified the effects of climate, bee and plant diversity, bee functional traits, network structure, and landscape configuration on bee and plant network resilience using a set of multi-model inference frameworks followed by structural equation models (SEM). We found that bee and plant species exhibited higher levels of network resilience at higher elevations. While bee network resilience increased linearly across the elevation gradient, plant network resilience increased exponentially from~1500 m and higher. Bee and plant network resilience increased in areas with reduced mean annual temperature (MAT) and decreased in areas with lower mean annual precipitation (MAP). Our SEM model showed that increasing temperatures indirectly influenced plant network resilience via network modularity and community assemblage of bees. We also found that MAP had a direct positive effect on plant diversity and network resilience, while the fragmentation of habitats reduced richness of plant communities and enhanced network modularity. In conclusion, we revealed that mutualistic networks showed higher network resilience at higher elevations. We also unveiled that climate and habitat fragmentation directly or indirectly influences the network resilience of plants and bees via the modulation of community assemblages and interaction networks. These influences are lower at higher elevations such that these systems seem better able to buffer against extinction cascades. We thus suggest that, management efforts should be geared at consolidating natural habitats. In contrast, restoration efforts should aim at mitigating climate change effects and harnessing the ability of mutualists to reconnect broken links to improve the network resilience and functioning of East-African montane ecosystems.
... The basic explanation is that if the various species in a community respond differently to environmental changes, then the decrease in one species in the community may be compensated by the increase in another species. Different mechanisms have been proposed to explain this variation in species responses (also response diversity, Elmqvist et al., 2003), including dissimilar responses of species to environmental fluctuation (de Mazancourt et al., 2013) or interspecific trade-offs in competitive abilities (Tilman, 1999). Empirical support for these mechanisms has been mixed, with studies showing positive (Carvalho et al., 2013;Spears et al., 2015;Van Ruijven & Berendse, 2010), negative (Isbell et al., 2015) and non-significant (Fischer et al., 2016;Isbell et al., 2015;Wagg et al., 2017) effects of species richness on resilience, which casts doubts about the generality of this positive relationship. ...
Aim
Understanding the mechanisms promoting resilience in plant communities is crucial in times of increasing disturbance and global environmental change. Here, we present the first meta‐analysis evaluating the relationship between functional diversity and resilience of plant communities. Specifically, we tested whether the resilience of plant communities is positively correlated with interspecific trait variation (following the niche complementarity hypothesis) and the dominance of acquisitive and small‐size species (following the mass ratio hypothesis), and for the context‐dependent effects of ecological and methodological differences across studies.
Location
Global.
Time Period
2004–2021.
Major Taxa Studied
Vascular plants.
Methods
We compiled a dataset of 69 independent sites from 26 studies that have quantified resilience. For each site, we calculated functional diversity indices based on the floristic composition and functional traits of the plant community (obtained from the TRY database) which we correlated with resilience of biomass and floristic composition. After transforming correlation coefficients to Fisher's Z ‐scores, we conducted a hierarchical meta‐analysis, using a multilevel random‐effects model that accounted for the non‐independence of multiple effect sizes and the effects of ecological and methodological moderators.
Results
In general, we found no positive functional diversity–resilience relationships of grand mean effect sizes. In contrast to our expectations, we encountered a negative relationship between resilience and trait variety, especially in woody ecosystems, whereas there was a positive relationship between resilience and the dominance of acquisitive species in herbaceous ecosystems. Finally, the functional diversity–resilience relationships were strongly affected by both ecological (biome and disturbance properties) and methodological (temporal scale, study design and resilience metric) characteristics.
Main Conclusions
We rejected our hypothesis of a general positive functional diversity–resilience relationship. In addition to strong context dependency, we propose that idiosyncratic effects of single resident species present in the communities before the disturbances and biological legacies could play major roles in the resilience of terrestrial plant communities.
Aims
Climate change‐induced changes in vegetation may be at first subtle and occur only locally within the ecosystem, complicating their reliable detection. We aimed to quantify short‐term changes in species and trait composition in a moss‐dominated ecosystem and to examine the associated uncertainty at the local and study area scales.
Location
Pristine boreal fen (Siikaneva) in Central Finland.
Methods
We applied the recently developed pre‐emptive joint species distribution model ( pJSDM ) to quantify the change in plant species and functional trait composition over 12 years. pJSDM allows spatially continuous prediction of change and the associated uncertainty from pointwise observations to the whole ecosystem. It includes the pre‐emptive competition for space within mosses that are an important component in many high‐latitude ecosystems. To address the mechanisms shaping the plant community, pJSDM was extended to predict the change in trait distribution parameters.
Results
Within the studied peatland, we detected changes in species and trait composition that were small in magnitude but occurred with high probability. Some of the changes occurred only locally, others over the whole study area, and some of the local changes occurred in opposing directions. The species originally found in the drier locations increased in abundance. Also, an increase in Sphagnum capitulum size was detected, indicating adaptation to drier conditions. The cover of wet‐adapted species decreased at the study area scale but displayed local increases.
Conclusions
The studied peatland showed nonuniform change in species and trait composition. The observed short‐term changes are in line with earlier descriptions of multidecadal drying and ombrotrophication of peatland vegetation and suggest increasing contrasts within the vegetation. The applied approach, pJSDM paired with trait distribution parameters, showed potential in revealing ongoing subtle changes in moss‐dominated vegetation.
Narrm‐Melbourne, Australia, has been at the forefront of urban biodiversity research, planning and management for 50 years in urban landscapes that have many endemic and threatened species and remnant ecosystems. Yet a range of emerging social and ecological challenges are emerging that must be addressed for Narrm‐Melbourne to continue to be a leader in urban biodiversity planning and practice.
Drawing on key insights from this work and our own experience working in research and practice, we explore three dimensions of urban biodiversity planning—land‐use planning, open space planning and conservation planning.
Key challenges currently being experienced include greater recognition of ecosystems as cultural landscapes and Traditional Owner rights, knowledge and practices; climate change and urban heat; and greater participation of a multicultural general public. These challenges also provide opportunities for achieving positive biodiversity outcomes at multiple scales that are consistent with the goals and targets of the Global Biodiversity Framework.
Practical implication. Innovations to the planning system that could help achieve these positive outcomes include decolonising biodiversity planning by recognising the cultural determinants of current ecosystem structure and function, and involving Traditional Owners in co‐management of urban landscapes. A greater focus on ecosystem function, resilience and connected multifunctional habitats will allow the planning system to move beyond its historic and conventional focus on local species and community composition. And finally, greater participation by and engagement with diverse local communities will increase diversity in decision‐making and can contribute to resilience and function.
Plant diversity plays a crucial role in maintaining the stability of ecological function. Based on field investigations and experimental analyses, artificial grassland plots with varying sowing times, adjacent natural grassland (CK), and open-pit coal mine dumps in the Muli mining area of Qinghai Province were selected as research subjects for this study. The characteristics of plant diversity and community stability were measured and analyzed, and the relationships between these factors and their influencing variables were evaluated. The results indicated significant differences in the vegetation community characteristics and plant diversity among the various grasslands. Coverage, aboveground biomass, belowground biomass, soil total nitrogen, and soil total carbon were the highest when the growth period was three years. Plant diversity and community stability in the natural grassland were significantly greater than that in the artificial grassland and open-pit coal mine dumps. A significant positive correlation was observed between plant diversity and community stability, suggesting that plant diversity can serve as an index of community stability. The order of stability, from highest to lowest, was CK > 11a > 10a > 8a > 9a > 6a > 7a > 3a > 2a > 1a > 0a. Years were identified as the primary factors affecting plant diversity and community stability by altering the soil pH. These results elucidate the relationships and driving mechanisms between plant diversity and community stability in grasslands, providing a scientific basis for maintaining community stability in artificial grassland ecosystems in alpine mining areas.
Urban land expansion is a major driver of many environmental and societal changes that challenge human well‐being and sustainable development, but its evolutionary process and dynamics are neither clear nor well‐integrated into urban science quantitatively. We analyzed the global urban extent data based on nighttime lights to examine the statistical distribution of urban land area at the global scale, and in 13 regions and countries over 29 years. The results reveal a converging temporal trend in urban land expansion from subnational to global scales, characterized by a coherent shift of urban area distribution from an initial power law toward an exponential distribution. This trend is well captured by a unified mathematical model based on the shifted power law distribution function and is reflected in the gradual predominance of medium‐size cities over small‐size cities in the configuration of urban systems across the world. The shift of urban area distributions bears the consequence of reduced urban system stability and resilience, and can be linked to increasing exposure of urban populations to extreme heat events and air pollution. These changes are likely to be driven by the increasing influence of external economies of scale associated with globalization. The findings challenge the status quo of land urbanization practices and emphasize the importance of medium‐size cities in urban planning.
Mutualisms may be more or less sensitive to environmental conditions depending on the diversity and responses of the species involved. Ants frequently form mutualistic associations with plants bearing extrafloral nectaries (EFNs): the ants protect the plants from herbivores and receive food resources (i.e., nectar) in return. As ectotherms, ants are strongly influenced by temperature, and temperature shifts can affect ant-plant interactions in ways that often depend on species functional traits. In this study, we explored the influence of EFN size and leaf surface temperature on ant-plant interactions in a Caatinga dry forest in Brazil. We observed the ants visiting 14 EFN-bearing plant species at different times of day over 12 sampling months; we also measured leaf surface temperatures during these periods. We next quantified EFN size for 68 individuals from the 14 plant species. The observational data were used to characterize the heat tolerance of the attendant ant species (i.e., based on levels of foraging activity). We then evaluated the mutualism’s degree of functional resilience using two indices: functional redundancy (i.e., the number of ant species interacting with a given plant species) and thermal response diversity (i.e., variability in the heat tolerance of the ant species interacting with a given plant species). We found that leaf surface temperature, but not EFN size, had an influence on mutualism functional resilience. As temperatures increased, both functional redundancy and thermal response diversity decreased. This result implies that warmer global temperatures could heighten the vulnerability of facultative ant-plant mutualisms, regardless of plant traits.
The gut microbiota of the pig is being increasingly studied due to its implications for host homeostasis and the importance of the pig as a meat source and biomedical model of human diseases. However, most studies comparing the microbiome between different breeds do not consider the influence of maternal environment during the colonization of the microbiota. The aim of the present study was to compare the gut microbiota during postnatal growth between two pig genotypes (purebred Iberian vs. crossbreds Iberian x Large White pigs), gestated in a single maternal environment (pure Iberian mothers) inseminated with heterospermic semen. Postnatally, piglets were maintained in the same environmental conditions, and their microbiota was studied at 60 and 210 days old. Results showed that age had the greatest influence on alpha and beta diversity, and genotype also affected beta diversity at both ages. There were differences in the microbiome profile between genotypes at the ASV and genus levels when jointly analyzing the total number of samples, which may help to explain phenotypical differences. When each time-point was analyzed individually, there were more differences at 210 days-old than 60 days-old. Fecal short-chain fatty acids (SCFA) were also affected by age, but not by genotype. These results may be a basis for further research on host genotype interactions with the gut microbiota.
This study explores sustainable housing solutions for urban areas in the Galapagos Islands, aiming to balance human needs with ecosystem preservation by fostering co-habitation between local communities and native species. Recognising the ecological importance of the Galapagos and the challenges posed by human-driven urban expansion, the research focuses on Puerto Ayora as a case study. It addresses material and spatial configurations that support key species such as giant tortoises, land iguanas, and sea lions. Computational strategies and simulations are employed to guide architectural, structural, and material decisions, including the use of evolutionary algorithms and selection strategies based on environmental performance metrics such as temperature, humidity, and solar radiation. These algorithms enhance architectural performance, facilitating co-habitation between humans and animals, with an emphasis on modularity and adaptability in architectural morphology. The results indicate that current configurations meet the habitat requirements for giant tortoises year-round. However, adjustments are needed for other species during specific months. The study also highlights bioceramic as a novel material for environmentally aligned construction in restricted environments. Limitations include focusing only on keystone species, with recommendations for future research to address the multispecies impact and integrate desalination and waste management systems for extracting the primary chemical component of bioceramic. This work advances the understanding of multispecies architectural design in ecologically sensitive regions, positioning the Galapagos as a model for sustainable co-habitation in conservation-focused development.
Substantial evidence suggests that biodiversity can stabilize ecosystem function, but how it does this is less clear. In very general terms, the hypothesis is that biodiversity stabilizes function because having more species increases the role of compensatory dynamics, which occur when species in a community show different responses to the environment. Here, we focus on two forms of compensatory dynamics, cross‐scale redundancy (CSR) and response diversity (RD). CSR occurs when species respond to a disturbance at different scales such that scale‐specific disturbances do not negatively affect all species. RD occurs when species contributing to the same function show different responses to an environmental change. We developed a new analytical approach that can compare the strength of CSR and RD in the same dataset and used it to study native bee pollination of blueberry at 16 farms that varied in surrounding agricultural land use. We then asked whether CSR and RD among bee species are associated with the stability of blueberry pollination. Although CSR and RD were both present, only RD was associated with higher stability of pollination. Furthermore, the effects of RD on stability were due to a single widespread species, Andrena bradleyi, that is a specialist on blueberry and, unlike other bee species, was highly abundant at farms surrounded by intensive blueberry agriculture. Thus, the stabilizing effect we observed was attributable to an “identity effect” more than to species richness per se. Our results demonstrate how CSR and RD can be empirically measured and compared and highlight how the theoretical expectations of the biodiversity–ecosystem functioning field are not always upheld when confronted with real‐world data.
Perturbations such as climate change, invasive species and pollution, impact the functioning and diversity of ecosystems. However diversity has many meanings, and ecosystems provide a plethora of functions. Thus, on top of the various perturbations that global change represents, there are also many ways to measure a perturbation’s ecological impact. This leads to an overwhelming response variability, which undermines hopes of prediction. Here, we show that this variability can instead provide insights into hidden features of functions and of species responses to perturbations. By analysing a dataset of global change experiments in microbial soil systems we first show that the variability of functional and diversity responses to perturbations is not random; functions that are mechanistically similar tend to respond coherently. Furthermore, diversity metrics and broad functions (e.g. total biomass) systematically respond in opposite ways. We then formalise these observations to demonstrate, using geometrical arguments, simulations, and a theory-driven analysis of the empirical data, that the response variability of ecosystems is not only predictable, but can also be used to access useful information about species contributions to functions and population-level responses to perturbations. Our research offers a powerful framework for understanding the complexity of ecological responses to global change.
The diversity in organismal responses to environmental changes (i.e., response diversity) plays a crucial role in shaping community and ecosystem stability. However, existing measures of response diversity only consider a single environmental variable, whereas natural communities are commonly exposed to changes in multiple environmental variables simultaneously. Thus far, no approach exists to integrate multifarious environmental change and the measurement of response diversity. Here, we show how to consider and quantify response diversity in the context of multifarious environmental change, and in doing so introduce a distinction between response diversity to a defined or anticipated environmental change, and the response capacity to any possible set of (defined or undefined) future environmental changes. First, we describe and illustrate the concepts with empirical data. We reveal the role of the trajectory of environmental change in shaping response diversity when multiple environmental variables fluctuate over time. We show that, when the trajectory of the environmental change is undefined (i.e., there is no information or a priori expectation about how an environmental condition will change in future), we can quantify the response capacity of a community to any possible environmental change scenario. That is, we can estimate the capacity of a system to respond under a range of realistic or extreme environmental changes, with utility for predicting future responses to even multifarious environmental change. Finally, we investigate determinants of response diversity within a multifarious environmental change context. We identify factors such as the diversity of species responses to each environmental variable, the relative influence of different environmental variables and temporal means of environmental variable values as important determinants of response diversity. In doing so, we take an important step towards measuring and understanding the insurance capacity of ecological communities exposed to multifarious environmental change.
Context
Characterizing landscape ecological complexity and change requires integrated description of spatial and temporal landscape organization and dynamics, as suggested by the shifting mosaic concept. Remotely sensed land surface phenology allows the detection of even small differences among landscape patches and through time, allowing for the analysis of landscapes as shifting mosaics.
Objectives
We sought to quantify aspects of the complex landscape behaviors that are implied by spatiotemporal variation in land surface phenology. We adapted an information-theoretic (IT) framework from ecosystem ecology to capture landscape-level spatiotemporal complexity and organization and map these properties across large areas.
Methods
Phenology data were derived from remotely sensed, pixel-level time series of a vegetation greenness index, across a large portion of North America. We summarized multi-year, multi-pixel dynamics in transition matrices, calculated IT metrics from the matrices, and used matrix projection to quantify disequilibrium dynamics and long-term trajectories of the metrics.
Results
Mapping the IT metrics and their disequilibria revealed gradients in the spatiotemporal complexity and organization of multi-year land surface phenology dynamics at continental to local scales. These gradients suggest influences of biophysical and biogeographic setting, ecological development and disturbances, land use, and other drivers of landscape ecological dynamics. The spatiotemporal IT metrics were influenced by both year-to-year dynamics and spatial landscape heterogeneity, but correlations with spatial and temporal complexity measures varied among the IT metrics. Landscapes showing the strongest disequilibrium dynamics were mostly in the western part of the continent and appeared to be associated with large-scale disturbances including severe fire, forest pathogens, climate variability, and land use change—important subjects for further study.
Conclusions
This approach reveals novel features of the shifting landscape mosaic, with implications for understanding landscape resilience and sustainability. Resulting spatial data products describing long-term landscape dynamics have potential applications in broad-scale ecological modeling, monitoring, assessment, and prediction.
Fish diversity and water quality are vital indicators of the health of freshwater ecosystems, however these systems are increasingly threatened by environmental changes and anthropogenic activities. This investigation aimed to assess the fish diversity and evaluate the physicochemical parameters of water at Ghazi Swabi near Tarbela Dam, River Indus, Khyber Pakhtunkhwa, Pakistan, between March and June 2020. Monthly water samples were collected and analyzed for various physicochemical parameters such as temperature, dissolved oxygen (DO), total dissolved solids (TDS), pH, turbidity, salinity, and concentrations of heavy metals including lead (Pb), copper (Cu), cadmium (Cd), and mercury (Hg). Using various nets and traps the fish specimens were collected with the help of local fishermen. Morphometric and meristic analyses were conducted to identify the species, while systematic keys were used to remove misidentifications. A total of 110 fish specimens were collected, representing 7 species across 6 genera, 3 families, and 3 orders. The family Cyprinidae was the most abundant, with species including Puntius conchonius, Puntius waageni, Crossocheilus diplocheilus, Barilius modestus, and Aspidoparia morar. The Belonidae family was represented by Xenentodon cancila, and the Ambassidae family by Chanda nama. Physicochemical analysis showed that the water quality remained within permissible limits for aquatic life, however higher levels of certain heavy metals were detected, which may pose long-term risks. The study concluded that the fish diversity at Ghazi Swabi near Tarbela Dam reflects a moderately healthy ecosystem, the presence of heavy metals in the water raises concerns about future ecological health. Regular monitoring and mitigation efforts are recommended to preserve biodiversity and maintain water quality. The study suggests the need for sustainable management practices to protect freshwater ecosystems from anthropogenic impacts.
The energy, utilities, industrial, and material sectors are crucial suppliers of essential goods and services, but their business operations are among the largest sources of anthropogenic greenhouse gas emissions. Consequently, companies in these sectors play a pivotal role in the low-carbon transition and face substantial stakeholder pressure to manage their transition risks and reduce their environmental impact. Here, we argue that effective responses to transition challenges require diversifying investments in adaptation and mitigation initiatives across a broad range of activities and goals. Analysing financial and nonfinancial data from a global sample of publicly traded companies, we find that those who extensively diversify their investments are better able to reduce their emissions over time. Diversification also reduces carbon pricing risk, thereby lowering exposure to transition risks, under several climate policy scenarios. Our findings provide empirical evidence that business leaders in critical sectors for the low-carbon transition should incorporate well-diversified investments in adaptation and mitigation initiatives into their sustainability strategies to manage interconnected transition challenges.
It remains unknown how species’ populations across their geographic range are constrained by multiple coincident natural and anthropogenic environmental gradients. Conservation actions are likely undermined without this knowledge because the relative importance of the multiple anthropogenic threats is not set within the context of the natural determinants of species’ distributions. We introduce the concept of a species ‘shadow distribution’ to address this knowledge gap, using explainable artificial intelligence to deconstruct the environmental building blocks of current species distributions. We assess shadow distributions for multiple threatened freshwater fishes in Switzerland which indicated how and where species respond negatively to threats — with negative threat impacts covering 88% of locations inside species’ environmental niches leading to a 25% reduction in environmental suitability. Our findings highlight that conservation of species’ geographic distributions is likely insufficient when biodiversity mapping is based on species distribution models, or threat mapping, without also quantifying species’ expected or shadow distributions. Overall, we show how priority actions for nature’s recovery can be identified and contextualised within the multiple natural constraints on biodiversity to better meet national and international biodiversity targets.
In Utah, and much of the Intermountain West, riparian forests make up a small percentage of the landscape but provide disproportionately large ecological functions and societal values. Since the early 1800s, Utah’s riparian forests have experienced shifts in natural disturbance regimes, changes in flow regimes and water tables, changes in vegetation composition and structure, introduction of exotic plant and animal species, and land use conversion. Today, managers need science-based guidance to assess ecological integrity, detect causes of degradation, and select appropriate methods for restoration of ecosystem processes and functions as well as the structure and composition of riparian forests. In this document, we provide a step-by-step process for making decisions about riparian forest restoration. These steps include (1) identification of forest vegetation types and hydrogeomorphic valley types, (2) identification of symptoms of degraded ecological integrity, (3) determination of stressors causing degradation, (4) selection of the appropriate management response(s) based on the symptoms and stressors present, and (5) selection of appropriate methods for collecting baseline data and monitoring management results. This process will assist managers in improving the ecological integrity and resilience in the face of current and future stressors.
Agricultural landscapes have been shaped by gradual, partially optimized changes in farms and surrounding areas which have resulted in fragmented agricultural landownership and increased distances on farms. Since Finland joined the EU in 1995, the average farm size has more than doubled which has increased the distances on farms. This may have caused trade-offs with resource use efficiency, productivity, and sustainability. The aim of this study was to evaluate the potential and impacts of land reallocation by integrating regional variability, logistical factors, and emerging satellite imagery, with an emphasis on enhancing resilience in future climates. This study estimated the theoretical potential for land reallocation between farms to reduce farmland fragmentation but also applied fixed land exchange rates (5 % to 40 %) with the primary aim to reduce distances within each farm depending on the farm size and region. The aim was also to identify co-benefits and trade-offs on the number of parcels in a farm, the production capacity of exchanged parcels, diversification potential, and the proximity of parcels to waterways. While keeping the farm size constant, large potential was found to optimize fragmented landscapes and reduce distances within farms especially on large farms. However, only a moderate exchange rate of 5 % almost halved the distances in the best cases of the farms, while exchange rates >20 % provided less additional logistic benefits. Thereby, modest, well targeted measures are not only more acceptable to landowners but may provide the most benefits with fewer trade-offs. In unsatisfactory cases, large parcels were replaced by higher numbers of smaller ones, productivity differences occurred, and closer parcels became more uniform, which may reduce diversification options, which are important for resilience and sustainability. Hence, merging and reshaping nearby parcels after reallocation might be needed to complete rationalization. Estimated changes in the proximity of the parcels to waterways tended to improve the farmers’ readiness to implement irrigation as an adaptation measure to climate change. The variable outcome of parcel reallocation emphasizes the central role of the current customer-driven consolidation system chaired by independent land surveyors to boost the land reallocation also in the future to improve logistics, resource efficiency, and sustainability on farms that today struggle with cost-crises.
This study looks into the interactions between environmental conditions and climate change, as well as their combined effects on plant and vegetation development patterns in ecologically sensitive areas. We investigate how temperature, precipitation, and atmospheric CO2 levels affect vegetation dynamics in a variety of ecosystems by combining data from satellite imagery, ground-based observations, and climate models. Our findings underscore these regions’ susceptibility to climate-induced stresses, with considerable changes in species distribution, phenology, and productivity. The study emphasizes the importance of adaptive management strategies to mitigate adverse effects and enhance the resilience of these critical ecosystems. This research contributes to a deeper understanding of the complex interactions between climate variables and ecological responses, providing a foundation for informed conservation and policy-making efforts in the face of global climate change.
Variations in vegetation composition and structure are significant signals of the succession of mudflat ecosystems and have important indicative roles in mudflat ecosystem degradation. Due to poor accessibility of vast even mudflat areas, variation in vegetation composition and structure across mudflat areas remains unclear in the Yellow River Delta (YRD), China. We provided an UAV multispectral orthomosaic with 10 cm ground sample distance to classify and compare the vegetation composition and structure across mudflat areas in the YRD. The vegetation classification overall accuracy achieved 95.0%. We found that although a significant difference (p < 0.05) was checked out in terms of the Shannon–Wiener diversity index (from 1.33 to 0.92) and evenness index (from 0.96 to 0.66) among the eight subareas from land to sea, all four dominant vegetation communities (S. salsa, L. bicolor, T. chinensis, and P. australis) were discovered at all eight subareas. Our findings support the idea that the regional environment and local microtopography are the predominant forces for variation in vegetation composition and structure across mudflat areas. From the perspective of vegetation restoration and conservation, changing the local microtopography will be an interesting way to enhance the vegetation diversity of the mudflat ecosystems in the YRD.
Salt-sensitive trees in coastal wetlands are dying as forests transition to marsh and open water at a rapid pace. Forested wetlands are experiencing repeated saltwater exposure due to the frequency and severity of climatic events, sea-level rise, and human infrastructure expansion. Understanding the diverse responses of trees to saltwater exposure can help identify taxa that may provide early warning signals of salinity stress in forests at broader scales. To isolate the impacts of saltwater exposure on trees, we performed an experiment to investigate the leaf-level physiology of six tree species when exposed to oligohaline and mesohaline treatments. We found that species exposed to 3–6 parts per thousand (ppt) salinity had idiosyncratic responses of plant performance that were species-specific. Saltwater exposure impacted leaf photochemistry and caused early senescence in Acer rubrum, the most salt-sensitive species tested, but did not cause any impacts on plant water use in treatments with <6 ppt. Interestingly, leaf spectral reflectance was correlated with the operating efficiency of photosystem II (PSII) photochemistry in A. rubrum leaves before leaf physiological processes were impacted by salinity treatments. Our results suggest that the timing and frequency of saltwater intrusion events are likely to be more detrimental to wetland tree performance than salinity concentrations.
Grasslands support multiple ecosystem functions and services, and diverse biota, and are critical for human well-being. Grazing is the most pervasive land use in grasslands, but can have damaging effects when poorly managed. How grazing management and the environment interact to affect ecosystem functions globally is less well understood. Addressing this knowledge gap is important if we are to evaluate where (climate region, soil texture, and grassland type), what (livestock type), and how (grazing intensity, grazing regime, and duration) grazing might minimize grassland degradation and sustain healthy grassland functions. We used a systematic meta-analysis to explore the effects of grazing on ecosystem functions (primary production, carbon sequestration, water conservation, nutrient cycle, and decomposition) based on 3917 paired data from 148 studies across the globe. We found that grazing substantially reduced plant productivity (-26 %), followed by water conservation (-18 %) and carbon sequestration (-19 %). The value of most ecosystem functions declined with increasing grazing intensity, and more pronounced negative effects of grazing with mixed-herbivore than single species grazing. Grazing impacts also varied with environmental conditions, with light grazing increasing carbon sequestration in arid regions, but reducing it in semi-arid regions. Further, increasing aridity indirectly weakened the positive impacts of light grazing on ecosystem functions by suppressing grazing effects. Our study suggests that the interactions between grazing management and environmental conditions are critical when assessing the effects of grazing on grassland functions, and this will likely be more important as climates become hotter and drier.
Aim
The assembly of real‐world ecological communities in human‐modified landscapes is influenced by a complex interplay of spatial, temporal, environmental and invasion gradients. However, understanding the relative importance of these drivers and their interactions in shaping functional assembly remains elusive. Our study aimed to investigate the relative influence of these drivers on the functional assembly of a stream fish metacommunity.
Location
Streams of the Lake Balaton catchment, Hungary.
Methods
We analysed a long‐term (18‐year) dataset of the stream fish metacommunity, focusing on changes in functional diversity (Q), redundancy (R) and species dominance (D). Ternary diagrams were utilized to decompose functional diversity into Q, R and D components and to visualize diversity patterns. Linear mixed‐effect regression and separate structural equation models were employed to identify significant drivers of Q, R and D.
Results
Native fish communities exhibited low functional diversity (Q) but high redundancy (R) and dominance (D), indicating functional convergence and dominance. Stream habitat size, network position and associated spatial, physical and chemical gradients emerged as consistently significant drivers of D and R. Changes in Q were additionally linked to non‐native community properties and subtle shifts in land use and within‐stream habitat characteristics.
Main Conclusions
Our findings suggest that both environmental filtering and interspecies interactions, particularly trait similarity between invaders and natives shape functional assembly of stream fish metacommunities. Despite minimal temporal directional changes, environmental drivers predominantly influence long‐term diversity patterns of native fish communities, overshadowing invasion effects. Our findings underscore the importance of considering both environmental filtering mechanisms and interspecies interactions in understanding functional assembly. Additionally, the joint application of diversity decomposition frameworks with predictive modelling provides comprehensive insight into patterns of functional diversity and assembly across ecological communities.
Hydrological connectivity in river systems facilitates the movement of animals across riverine landscapes and influences fish habitat but is threatened by climate change and water resource developments. We studied fish assemblages across a large wet–dry tropical river system in northern Australia that is under consideration for new agricultural and water resource developments, which are expected to alter hydrological connectivity. We explored relationships between the environment and several biotic variables; fish taxonomic composition, species turnover, and species trait presence, quantifying how they were related to hydrological connectivity. Environmental dissimilarity of sites was influenced by hydrological connectivity variables, including flow, elevation, and river distance. Environment characteristics and hydrological connectivity together were important predictors of fish taxonomic composition. Fish species turnover was highest in headwater sites, and species presence absence was related to feeding and reproductive traits. Our results suggest that habitat specialists and species with reproductive traits that depend on hydrological connectivity, such as diadromous species, are most vulnerable to declines in relative abundance following a reduction in connectivity, which would lead to range contractions within catchments. Maintaining habitats that support taxonomically and functionally unique fish assemblages, such as wetlands and headwater streams, is important for maintaining biodiversity.
Arboreal frugivores, such as primates and hornbills, are important seed dis- persers for many tropical plant species, yet the degree to which they use the same resources is unknown. If primates and hornbills consume the same fruit species, they may be redundant in their roles as seed dispersers, and the loss of one of these taxa may be compensated for by the other. To examine resource use by tropical frugivores, we quantified the feeding habits of two hornbill species, Ceratogymna atrata and C. cylindricus, and five primate species, Colobus guereza, Lophocebus albigena, Cercopithecus pogonias, C. cephus, and C. nictitans, in the lowland rainforest of south-central Cameroon. Based on over 2200 feeding observations recorded between January and December 1998, we characterized the diets and estimated dietary overlap among frugivore species. Previous studies have cal- culated dietary overlap by counting the number of diet species that two animals share, often leading to inflated estimates of overlap. Our method incorporated the proportional use of diet species and fruit availability into randomization procedures, allowing a clearer as- sessment of the actual degree of overlap. This added complexity of analysis revealed that, although the diets of a hornbill and a primate species may have as many as 36 plant species in common, actual dietary overlap is low. These results suggested that there are distinct hornbill and primate feeding assemblages, with primates consuming a greater diversity of plant species and higher levels of nonfruit items like leaves and seeds. Using Correspon- dence Analysis, we also identified two primate assemblages, separated largely by degree of frugivory and folivory. In addition, we found that hornbills feed at significantly higher strata in the forest canopy and eat fruits of different colors than primates. Averaged across the year, overlap between groups (hornbill-primate) was significantly lower than combined within-group overlap (primate-primate and hornbill-hornbill), showing that primates and hornbills have dissimilar diets and are not redundant as seed dispersers. In equatorial Africa, primate populations face greater declines than hornbill populations because of hunting. It is unlikely that seed dispersal by hornbills will compensate for the loss of primates in maintaining forest structure.
A simulation model, recent experiments, and the literature provide consistent evidence that megafauna extinctions caused by human hunting could have played as great a role as climate in shifting from a vegetation mosaic with abundant grass-dominated steppe to a mosaic dominated by moss tundra in Beringia at the end of the Pleistocene. General circulation models suggest that the Pleistocene environment of Beringia was colder than at the present with broadly similar wind patterns and precipitation but wetter soils. These and other observations suggest that the steppelike vegetation and dry soils of Beringia in the late Pleistocene were not a direct consequence of an arid macroclimate. Trampling and grazing by mammalian grazers in tundra cause a shift in dominance from mosses to grasses. Grasses reduce soil moisture more effectively than mosses through high rates of evapotranspiration. Results of a simulation model based on plant competition for water and light and plant sensitivity to grazers and nutrient supply predict that either of two vegetation types, grass-dominated steppe or moss-dominated tundra, could exist in Beringia under both current and Pleistocene climates. The model suggests that moss-dominated tundra is favored when grazing is reduced below levels that are in equilibrium with climate and vegetation. Together these results indicate that mammalian grazers have a sufficiently large effect on vegetation and soil moisture that their extinction could have contributed substantially to the shift from predominance of steppe to tundra at the Pleistocene-Holocene boundary. Our hypothesis suggests a mechanism by which the steppe ecosystem could be restored to portions of its former range. We also suggest that mammalian impacts on vegetation are sufficiently large that future vegetation cannot be predicted from climate scenarios without considering the role of mammals.
In order to assess how diversity changes over time at sites undergoing environmental change, we examined three data sets on long-term trends in taxonomic richness and composition: (1) 22 years of rodent censuses from a site in the Chihuahuan Desert of Arizona; (2) 50 years of bird surveys from a three-county region of northern Michigan; and (3) approximately 10,000 years of pollen records from two sites in Europe. In all three cases, richness has remained remarkably constant despite large changes in composition. The results suggest that while species composition may be highly variable and change substantially in response to environmental change, species diversity is an emergent property of ecosystems that is often maintained within narrow limits. Such regulation of diversity requires maintenance of relatively constant levels of productivity and resource availability and an open system with opportunity for compensatory colonizations and extinctions. In addition to studying the effects of diversity on biogeochemical processes, it will often be useful to think of species richness as an emergent consequence of ecosystem processes.
Resilience is the magnitude of disturbance that can be tolerated before a socioecological system (SES) moves to a different
region of state space controlled by a different set of processes. Resilience has multiple levels of meaning: as a metaphor
related to sustainability, as a property of dynamic models, and as a measurable quantity that can be assessed in field studies
of SES. The operational indicators of resilience have, however, received little attention in the literature. To assess a system's
resilience, one must specify which system configuration and which disturbances are of interest. This paper compares resilience
properties in two contrasting SES, lake districts and rangelands, with respect to the following three general features: (a)
The ability of an SES to stay in the domain of attraction is related to slowly changing variables, or slowly changing disturbance
regimes, which control the boundaries of the domain of attraction or the frequency of events that could push the system across
the boundaries. Examples are soil phosphorus content in lake districts woody vegetation cover in rangelands, and property
rights systems that affect land use in both lake districts and rangelands. (b) The ability of an SES to self-organize is related
to the extent to which reorganization is endogenous rather than forced by external drivers. Self-organization is enhanced
by coevolved ecosystem components and the presence of social networks that facilitate innovative problem solving. (c) The
adaptive capacity of an SES is related to the existence of mechanisms for the evolution of novelty or learning. Examples include
biodiversity at multiple scales and the existence of institutions that facilitate experimentation, discovery, and innovation.
We describe existing models of the relationship between species diversity and ecological function, and propose a conceptual
model that relates species richness, ecological resilience, and scale. We suggest that species interact with scale-dependent
sets of ecological structures and processes that determine functional opportunities. We propose that ecological resilience
is generated by diverse, but overlapping, function within a scale and by apparently redundant species that operate at different
scales, thereby reinforcing function across scales. The distribution of functional diversity within and across scales enables
regeneration and renewal to occur following ecological disruption over a wide range of scales.
Cross-scale resilience theory predicts that the combination of functional diversity within scales and functional redundancy
across scales is an important attribute of ecosystems because it helps these systems resist minor ecological disruptions and
regenerate after major disturbances such as hurricanes and fire. Using the vertebrate fauna of south Florida, we quantified
how the loss of native species and invasion by nonnatives may alter functional group richness within and across scales. We
found that despite large changes in species composition due to potential extinctions and successful invasions by nonnative
species, functional group richness will not change significantly within scales, there will not be any significant loss of
overall redundancy of ecology function across scales, and overall body mass pattern will not undergo substantial change. However,
the types of functions performed will change, and this change may have profound effects on not only the Everglades ecosystem
but on the entire landscape of south Florida.
The current rate of biodiversity loss threatens to disrupt greatly the functioning of ecosystems, with potentially significant consequences for humanity. The magnitude of the loss is generally measured with the use of species extinction rates, an approach that understates the severity of the problem and masks some of its most important consequences. Here, we propose a major expansion of this focus to include population diversity: considering changes in the size, number, distribution and genetic composition of populations and the implications of those changes for the functioning of ecosystems and the provision of ecosystem services. We also outline the key components of population diversity and describe a new approach to delineating a population unit that explicitly links it to the services that it provides
ONE of the ecological tenets justifying conservation of biodiversity is that diversity begets stability. Impacts of biodiversity on population dynamics and ecosystem functioning have long been debated1-7, however, with many theoretical explorations2-6,8-11 but few field studies12-15. Here we describe a long-term study of grasslands16,17 which shows that primary productivity in more diverse plant communities is more resistant to, and recovers more fully from, a major drought. The curvilinear relationship we observe suggests that each additional species lost from our grasslands had a progressively greater impact on drought resistance. Our results support the diversity-stability hypothesis5,6,18,19, but not the alternative hypothesis that most species are functionally redundant19-21. This study implies that the preservation of biodiversity is essential for the maintenance of stable productivity in ecosystems.
All species have evolved in the presence of disturbance, and are thus in a sense matched to the recurrence pattern of the perturbations. Consequently, disturbances within the typical range, even at the extreme of that range as defined by large infrequent disturbances (LID's), usually result in little long-term change to the systems fundamental character. We argue that more serious ecological consequences result from compounded perturbations within the normative recovery time of the community in question. We consider both physically based disturbance (for example storm, volcanic eruption, and forest fire) and biologically based disturbance of populations such as overharvesting, invasion, and disease, and their interactions. Dispersal capability and measures of generation time or age to first reproduction of the species of interest seem to be important metrics for scaling the size and frequency of disturbances among different types of ecosystems. We develop six scenarios that describe describe communities that have been subject to multiple perturbations, either similtaneously or at a faster rate than the rate of recovery, and appear to have entered new domains or "ecological surprises". In some cases. three of more disturbances seem to have been required to initiate the changed state. We argue that in a world of ever-more -pervasive anthropogenic impacts on natural communities coupled with the ever increasing certainty of global change, compounded perturbations and ecological surprises will become more common. Understanding these ecological synergisms will be basic to envirnmental, management decisions of the 21st century.
A rich mammalian fauna is found on islands that lie on the Sunda Shelf, a continental shelf extending from Vietnam to Borneo and Java that was periodically exposed as dry land during the Pleistocene. The correlation between log of island area and number of species is high (r
2=0.94); the slope of the curve is moderate (z=0.235). Distance from small islands to “source areas” (=Borneo, Sumatra, and the Malay Peninsula) does not appear to affect species richness, nor does depth of water to source area (a measure of isolation time). A species-area curve for forest reserves of varying sizes on the Malay Peninsula has a low slope (z=0.104); comparison of the mainlaind and island curves indicates that decreasing island area is strongly correlated with increased extinction. Extinction has left reduced but ecologically balanced sets of species on all islands, except that carnivores are under-represented on all but the largest islands. Initial body size and rarity appear to play a significant role in determining the probability of extinction of individual species.
Investigating the effect of biodiversity on the stability of ecological communities is complicated by the numerous ways in which models of community interactions can be formulated. This has led to differences in conclusions and interpretations of how the number of species in a community affects its stability. Here, we derive a simple, general relationship between the coefficient of variation (CV) of combined species densities and the environmentally driven variability in species' per capita population growth rates. For a given level of environmentally driven variability in per capita population growth rates, increasing the number of species in a community decreases the CV of combined species densities, provided that species do not respond to environmental fluctuations in a perfectly correlated way. Thus, a community with more species of competitors will be more stable (have lower CV in combined species densities for a given level of environmental variability) than a species-poor community, provided that the species in both communities show equal variability in per capita population growth rates and provided that species within each community do not show strongly correlated responses to environmental fluctuations. This conclusion also applies to "noninteractive" models in which there is no competition between species.
The ecological consequences of biodiversity loss have aroused considerable interest and controversy during the past decade. Major advances have been made in describing the relationship between species diversity and ecosystem processes, in identifying functionally important species, and in revealing underlying mechanisms. There is, however, uncertainty as to how results obtained in recent experiments scale up to landscape and regional levels and generalize across ecosystem types and processes. Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments. A major future challenge is to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.
The manner in which terrestrial ecosystems are regulated is controversial. The "top-down" school holds that predators limit herbivores and thereby prevent them from overexploiting vegetation. "Bottom-up" proponents stress the role of plant chemical defenses in limiting plant depredation by herbivores. A set of predator-free islands created by a hydroelectric impoundment in Venezuela allows a test of these competing world views. Limited area restricts the fauna of small (0.25 to 0.9 hectare) islands to predators of invertebrates (birds, lizards, anurans, and spiders), seed predators (rodents), and herbivores (howler monkeys, iguanas, and leaf-cutter ants). Predators of vertebrates are absent, and densities of rodents, howler monkeys, iguanas, and leaf-cutter ants are 10 to 100 times greater than on the nearby mainland, suggesting that predators normally limit their populations. The densities of seedlings and saplings of canopy trees are severely reduced on herbivore-affected islands, providing evidence of a trophic cascade unleashed in the absence of top-down regulation.
1 Maximiliana maripa is a large seeded palm that occurs in monodominant patches (clumps) in the Amazonian forest of Maraca Island, Roraima, Brazil. 2 Rodents, collared peccaries (Tayassu tajacu), deer (Odocoileus virginiamus and Mazama spp.) and primates, all short-distance, small-to-medium bodied dispersers, ate the pulp of Maximiliana fruits and spat out intact seeds, from 97 to 100% of them within 5 m of parent plants (below the tree crown). 3 Tapirs (Tapirus terrestris) swallowed entire fruits and defecated intact seeds at latrines located up to 2 km from the nearest palm clump, creating a large-scale, punctuated seed shadow. 4 Bruchid beetle (Pachymeris cardo) larvae killed 77% of seeds remaining near parent trees, but only 0.7% of the 6140 seeds dispersed by tapirs to latrines. 5 Densities of zero-year seedlings to fifth-year saplings were significantly higher at tapir latrine sites than around parent trees located in conspecific aggregations; they were also significantly higher for the zero and one year classes at latrines than at randomly selected nonpalm, nonlatrine control trees. 6 Seeds dispersed by tapirs to latrines and secondarily dispersed by rodents gave rise to the seedlings and saplings located around the latrine sites, while seeds secondarily dispersed by rodents gave rise to the seedlings and saplings around control trees. 7 Collared (Tayassu tajacu) and white-lipped (T. pecari peccaries accounted for high seedlings and saplings mortality around parent trees. 8 Adult Maximiliana attained densities of 32 trees per 2500 m 2 within these patches. 9 Clump dispersal of seeds by tapirs, a meso-scale process, interacting with the small-scale process of seed dispersal by rodents, is sufficient to explain the creation of palm patches.
Ecosystems that are managed for resource production are under continual structural change. Changes imposed by local management aggregate to produce regional patterns and new regionwide responses. Anthropogenic influences on hemispheric and global processes add another level of change. The result is a bewildering variety of real or anticipated changes unique to experience. For example, in the spruce/fir and budworm interaction of eastern North America, a syndrome of causes affects the vulnerability of renewable resources, and the triggers of change can never be predicted. Yet, it is possible to identify key features that affect resilience of ecosystems and robustness of regulation and to reject other possibilities. This approach provides a way to assign priorities for research and for contingency planning to adapt to change.
In the Experimental Lakes Area, phytoplankton production in the 2 eutrophied lakes was higher than in reference lakes. It decreased quickly to background values when fertilization was terminated. Winter respiration was unchanged, P/R ratios were constant under constant N/P fertilization, but decreased for 3 yr after the N/P ratio in fertilizer was decreased from 14:1 to 5:1 by weight. Phytoplankton production was not affected by acidification to a pH of 5.0. Winter respiration declined at pH values ≤5.1, causing P/R to be highest at the lowest pH values. Respiration returned to normal when the pH of the lake was increased to 5.4. Gross periphyton production and respiration both increased with acidification, but P/R ratios declined at pH values <6.2. Nitrification in both acidified lakes ceased at pH values of 5.4-5.7. It recovered when pH was allowed to increase, but with a time lag of one year. No other nutrient cycles appeared to be disrupted. Both eutrophication and acidification caused declines in species diversity among several taxonomic groups. Among phytoplankton, both stresses caused an increase in size of organisms in summer. Among higher taxa, there was not a consistent tendency for either small or large organisms to be favored. Periphyton metabolism was the most sensitive indicator of acidification, followed by taxonomic changes in several groups. Ecosystem-level production and respiration were the most resistant properties to acid stress. The earliest serious changes in ecosystems and food webs occurred when acidification eliminated acid-sensitive organisms that were also the sole occupants of key ecological niches. Such situations occur frequently in northern lakes. -from Author
Multiscale patterns of spatial and temporal variation in density and population structure were used to evaluate the generality of a three-trophic-level cascade among sea otters (Enhydra lutris), invertebrate herbivores, and macroalgae in Alaska. The paradigm holds that where sea otters occur herbivores are rare and plants are abundant, whereas when sea otters are absent herbivores are relatively common and plants are rare. Spatial patterns were based on 20 randomly placed quadrats at 153 randomly selected sites distributed among five locations with and four locations without sea otters. Both sea urchin and kelp abundance differed significantly among locations with vs. without sea otters in the Aleutian Islands and southeast Alaska. There was little (Aleutian Islands) or no (southeast Alaska) overlap between sites with and without sea otters, in plots of kelp density against urchin biomass. Despite intersite variation in the abundance of kelps and herbivores, these analyses demonstrate that sea otter predation has a predictable and broadly generalizable influence on the structure of Alaskan kelp forests. The percent cover of algal turf and suspension feeder assemblages also differed significantly (although less dramatically) between locations with and without sea otters. Temporal variation in community structure was assessed over periods of from 3 to 15 yr at sites in the Aleutian Islands and southeast Alaska where sea otters were 1) continuously present, 2) continuously absent, or 3) becoming reestablished because of natural range expansion. Kelp and sea urchin abundance remained largely unchanged at most sites where sea otters were continuously present or absent, the one exception being at Torch Bay (southeast Alaska), where kelp abundance varied significantly through time and urchin abundance varied significantly among sites because of episodic and patchy disturbances. In contrast, kelp and sea urchin abundances changed significantly, and in the expected directions, at sites that were being recolonized by sea otters. Sea urchin biomass declined by 50% in the Aleutian Islands and by nearly 100% in southeast Alaska following the spread of sea otters into previously unoccupied habitats. In response to these different rates and magnitudes of urchin reduction by sea otter predation, increases in kelp abundance were abrupt and highly significant in southeast Alaska but much smaller and slower over similar time periods in the Aleutian Islands. The different kelp colonization rates between southeast Alaska and the Aleutian Islands appear to be caused by large-scale differences in echinoid recruitment coupled with size-selective predation by sea otters for larger urchins. The length of urchin jaws (correlated with test diameter, r^2 = 0.968) in sea otter scats indicates that sea urchins <15-20 mm test diameter are rarely eaten by foraging sea otters. Sea urchin populations in the Aleutian Islands included high densities of small individuals (<20 mm test diameter) at all sites and during all years sampled, whereas in southeast Alaska similarly sized urchins were absent from most populations during most years. Small (<30-35 mm test diameter) tetracycline-marked urchins in the Aleutian Islands grew at a maximum rate of @?10 mm/yr; thus the population must have significant recruitment annually, or at least every several years. In contrast, echinoid recruitment in southeast Alaska was more episodic, with many years to perhaps decades separating significant events. Our findings help explain regional differences in recovery rates of kelp forests following recolonization by sea otters.
This paper considers the significance of biological diversity in relation to large-scale processes in complex and dynamic ecological-economic systems. It focuses on functional diversity, and its relation to production and maintenance of ecological services that underpin human societies. Within functional groups of organisms two important categories of species are identified: keystone process species and those essential for ecosystem resilience. The latter group represents ''natural insurance capital.'' In addition to basic research on the interplay among biological diversity, functional performance, and resilience in complex self-organizing systems, we suggest that a functional approach has two main implications for a strategy for biodiversity conservation: (1) Biodiversity conservation to assure the resilience of ecosystems is required for all systems, no matter how heavily impacted they are. It should not be limited to protected areas. (2) The social, cultural, and economic driving forces in society that cause biodiversity loss need to be addressed directly. Specifically, (a) differences between the value of biological diversity to the private individual and its fundamental value to society as a whole need to be removed; (b) social and economic policies that encourage biodiversity loss should be reformed, especially where there is a risk of irreversible damage to ecosystems and diversity; and (c) institutions that are adaptive and work in synergy with ecosystem processes and functions are critical and should be created at all levels.
Addresses the problem of which biota to choose to best satisfy the conservation goals for a particular region in the face of inadequate resources. Biodiversity is taken to be the integration of biological variability across all scales, from the genetic, through species and ecosystems, to landscapes. The best way to minimize species loss is to maintain the integrity of ecosystem function. The important questions therefore concern the kinds of biodiversity that are significant to ecosystem functioning. To best focus our efforts we need to establish how much (or how little) redundancy there is in the biological composition of ecosystems. An approach is suggested, based on the use of functional groups of organisms defined according to ecosystem processes. Functional groups with little or no redundancy warrant priority conservation effort. -from Author
In order to investigate the impact of freshwater acidification on the trophic structure of macroinvertebrate communities, we performed a study on 22 forested headwater streams characterised by different degrees of acidification (mean pH = 4.49 to 6.98). Results showed that in acidic streams all functional feeding groups were affected in terms of taxonomic richness. As far as the population density was concerned, only a few acid‐tolerant taxa of shredders and predators showed an increasing abundance under acidic conditions. Trophic structure of acidified streams appeared to be deeply impacted with a large contribution of shredders and a complete disappearance of scrapers. In contrast, in circumneutral streams, we found that each functional feeding group had an almost equal share of the trophic web.
Aquatic ecologists have many models for size distributions of pelagic communities. However, few studies have looked for discontinuities (clumps of similarly sized species or gaps of sizes that contain no or relatively few species) in pelagic community size structure. We investigated size distribution characteristics in aquatic communities by calculating kernel density functions for plankton and fish in 11 lakes in Wisconsin. Size distributions in aquatic communities of these lakes were not smooth. Rather, multiple lump and gap regions were found within each functional group of phytoplankton, zooplankton, and fish. Simulations showed the gaps could not be explained by incomplete censuses of species or by systematic underestimation of intraspecific size variation. In an experimentally enriched lake, before and after comparisons showed lumps were not affected by large additions of P and N, even though biomass and production changed substantially. Lump regions in the two lakes with both food web manipulations and nutrient enrichment were substantially less similar pre- versus postenrichment than the reference lake and the lake with only nutrients added, but lump number remained relatively unchanged. Lakes that differed widely in nutrient status, trophic structure, species diversity, and area had similar size distributions. Comparisons of functional groups showed that phytoplankton had more lumps than zooplankton. In these north temperate lakes, size distribution characteristics seem to be conservative properties shaped by common regional ecosystem processes and organism patterns and not by lake-specific factors.
Flying foxes of the genus Pteropus (Pteropodidae: Chiroptera) play important roles as pollinators and seed dispersers in oceanic-island forest communities. This research examined general theories of diet breadth, diet selection, and the evolution of feeding strategies in bats in light of information from members of the genus Pteropus that inhabit oceanic islands. The feeding ecology of two species of flying fox, Pteropus samoensis and Pteropus tonganus on the Samoan archipelago, was examined in detail by direct observation and by examining feeding refuse. P. samoensis and P. tonganus fed on over 78 plant species from 39 families throughout their range and on over 69 plant species in Samoa alone. Flying foxes interacted with 59% of the forest tree species in Amalau Valley for fruit or flower resources. Twenty-eight percent of the forest trees were commonly used, and 79% of forest canopy trees were used. Broad overlap in resource use was noted between P. samoensis and P. tonganus with over 22 shared plant species. Seasonal variation in fruit resource use was quantified with a preference index. Flying foxes ate a taxonomically nonrandom subset of fruit species and generally preferred primary forest fruits to those in the secondary forest. Six plant families (Sapotaceae, Mrytaceae, Moraceae, Combretaceae, Fabaceae, and Sapindaceae) were particularly important to flying foxes in Samoa. However, a set of core plant taxa does not exist for Pteropus spp. in Samoa. Differences in the evolution of feeding strategies between mainland fruit-eating chiroptera and island species likely reflect differences in the spatio-temporal availability of resources in the two systems.
Biodiversity plays a vital role for ecosystem functioning in a
changing environment. Yet theoretical approaches that incorporate
diversity into classical ecosystem theory do not provide a general
dynamic theory based on mechanistic principles. In this paper, we
suggest that approaches developed for quantitative genetics can be
extended to ecosystem functioning by modeling the means and variances
of phenotypes within a group of species. We present a framework that
suggests that phenotypic variance within functional groups is linearly
related to their ability to respond to environmental changes. As a
result, the long-term productivity for a group of species with high
phenotypic variance may be higher than for the best single species,
even though high phenotypic variance decreases productivity in the
short term, because suboptimal species are present. In addition, we
find that in the case of accelerating environmental change, species
succession in a changing environment may become discontinuous. Our work
suggests that this phenomenon is related to diversity as well as to the
environmental disturbance regime, both of which are affected by
anthropogenic activities. By introducing new techniques for modeling
the aggregate behavior of groups of species, the present approach may
provide a new avenue for ecosystem analysis.
Species extinction in fragmented habitats is a non‐random process described by transient, rather than equilibrium dynamics. Therefore, ‘static’ approaches focusing on experimentally established spatial gradients of diversity may fail to capture essential aspects of ecosystem responses to species loss.
Here we document temporal changes in microarthropod species abundance, biomass and richness during a community disassembly trajectory following experimental habitat fragmentation of a moss‐based microecosystem.
Habitat fragmentation reduced heterotrophic species richness and community biomass in remnant moss fragments. Extinction was biased towards rare species, and thus occurred initially without significant changes in total community abundance and biomass. Eventual reductions in abundance and biomass were found to lag behind observed declines in species richness.
The presence of moss‐habitat corridors connecting fragments to a large ‘mainland’ area coupled with an immigration rescue effect maintained microarthropod richness, abundance and biomass within remnant fragments.
Our results indicate that both the order of species loss and the dynamics of remnant populations influence the magnitude and timing of ecosystem‐level responses to habitat destruction and isolation.
The South Pacific islands of Samoa have two extant flying fox species, Pteropus samoensis and P. tonganus. Following two severe cyclonic storms, we examined their differential behavioral responses and evaluated the effectiveness of recently established reserves in providing refugia. Although the cyclones disrupted activity patterns and foraging behavior for both species, comparisons with pre-storm data suggested that the more common, widely distributed P. tonganus experienced more severe population declines than the endemic P. samoenis. This differential mortality could be explained by a combination of ecological and behavioral factors. P. tonganus had a greater tendency to enter villages to feed on fallen cultivated fruits, making it more vulnerable to human hunting and predation by domestic animals. In addition, P. samoensis appeared to use survival strategies not observed in P. tonganus. Leaves, which were far more available than flowers or fruits in the immediate post-storm period, comprised a major part of the post-storm diet of P. samoensis. This species also fed on the fleshy bracts of a storm-resistant native liana, (Freycinetia reineckei). In contrast, a seasonally important food of P. tonganus is nectar from the delicate flowers of Syzygium inophylloides (asi), a canopy tree that is very vulnerable to wind damage and has become increasing scarce with the clearing of lowland forest. Rainforest reserves, established prior to the storms, served as adequate refugia for local P. samoensis populations, which appeared to feed relatively close to their roosts, primarily in native forest, but did not protect P. tonganus populations, which traveled outside reserves to forage in areas lacking hunting bans. Although wind damage was patchy and not consistent between storms, areas of high topographic complexity (e.g., volcanic cones and deep valleys) were the most likely to retain areas with some foliage and should be given priority in the design of future reserves.
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.
Large differences in community structure of sea urchins and finfish have been observed in Kenyan reef lagoons. Differences have been attributed to removal of finfish predators through human fishing activities. This study attempted to determine (i) the major sea urchin finfish predators, (ii) the effect of predation on sea-urchin community structure, and (iii) the possible effect of sea urchin increases and finfish decreases on the lagoonal substrate. Six reefs, two protected and four unprotected, were compared for differences in finfish abundance, sea urchin abundance and diversity and substrate cover, diversity and complexity. Comparisons between protected and unprotected reefs indicated that finfish populations were ca. 4 x denser in protected than unprotected reefs. Sea urchin populations were >100 x denser and predation rates on a sea urchin, Echinometra mathaei, were 4 x lower in unprotected than in protected reefs. The balistidae (triggerfish) was the single sea-urchin finfish predator family which had a higher population density in protected than in unprotected reefs. Balistid density was positively correlated with predation rates on tethered E. mathaei (r=0.88; p
Current natural resource management seldom takes the ecosystem functions performed by organisms that move between systems
into consideration. Organisms that actively move in the landscape and connect habitats in space and time are here termed “mobile
links.” They are essential components in the dynamics of ecosystem development and ecosystem resilience (that is, buffer capacity
and opportunity for reorganization) that provide ecological memory (that is, sources for reorganization after disturbance).
We investigated the effects of such mobile links on ecosystem functions in aquatic as well as terrestrial environments. We
identify three main functional categories: resource, genetic, and process linkers and suggest that the diversity within functional
groups of mobile links is a central component of ecosystem resilience. As the planet becomes increasingly dominated by humans,
the magnitude, frequency, timing, spatial extent, rate, and quality of such organism-mediated linkages are being altered.
We argue that global environmental change can lead to (a) the decline of essential links in functional groups providing pollination,
seed dispersal, and pest control; (b) the linking of previously disconnected areas, for example, the spread of vector-borne
diseases and invasive species; and (c) the potential for existing links to become carriers of toxic substances, such as persistent
organic compounds. We conclude that knowledge of interspatial exchange via mobile links needs to be incorporated into management
and policy-making decisions in order to maintain ecosystem resilience and hence secure the capacity of ecosystems to supply
the goods and services essential to society.
This study tested an hypothesis concerning patterns in species abundance in ecological communities. Why do the majority of
species occur in low abundance, with just a few making up the bulk of the biomass? We propose that many of the minor species
are analogues of the dominants in terms of the ecosystem functions they perform, but differ in terms of their capabilities
to respond to environmental stresses and disturbance. They thereby confer resilience on the community with respect to ecosystem
function. Under changing conditions, ecosystem function is maintained when dominants decline or are lost because functionally
equivalent minor species are able to substitute for them. We have tested this hypothesis with respect to ecosystem functions
relating to global change. In particular, we identified five plant functional attributes—height, biomass, specific leaf area,
longevity, and leaf litter quality—that determine carbon and water fluxes. We assigned values for these functional attributes
to each of the graminoid species in a lightly grazed site and in a heavily grazed site in an Australian rangeland. Our resilience
proposition was cast in the form of three specific hypotheses in relation to expected similarities and dissimilarities between
dominant and minor species, within and between sites. Functional similarity—or ecological distance—was determined as the euclidean
distance between species in functional attribute space. The analyses provide evidence in support of the resilience hypothesis.
Specifically, within the lightly grazed community, dominant species were functionally more dissimilar to one another, and
functionally similar species more widely separated in abundance rank, than would be expected on the basis of average ecological
distances in the community. Between communities, depending on the test used, two of three, or three of four minor species
in the lightly grazed community that were predicted to increase in the heavily grazed community did in fact do so. Although
there has been emphasis on the importance of functional diversity in supporting the flow of ecosystem goods and services,
the evidence from this study indicates that functional similarity (between dominant and minor species, and among minor species)
may be equally important in ensuring persistence (resilience) of ecosystem function under changing environmental conditions.
There have been several earlier studies that addressed the influence of natural disturbance regimes on coral reefs. Humans
alter natural disturbance regimes, introduce new stressors, and modify background conditions of reefs. We focus on how coral
reef ecosystems relate to disturbance in an increasingly human-dominated environment. The concept of ecosystem resilience—that
is, the capacity of complex systems with multiple stable states to absorb disturbance, reorganize, and adapt to change—is
central in this context. Instead of focusing on the recovery of certain species and populations within disturbed sites of
individual reefs, we address spatial resilience—that is, the dynamic capacity of a reef matrix to reorganize and maintain
ecosystem function following disturbance. The interplay between disturbance and ecosystem resilience is highlighted. We begin
the identification of spatial sources of resilience in dynamic seascapes and exemplify and discuss the relation between “ecological
memory” (biological legacies, mobile link species, and support areas) and functional diversity for seascape resilience. Managing
for resilience in dynamic seascapes not only enhances the likelihood of conserving coral reefs, it also provides insurance
to society by sustaining essential ecosystem services.
The consequences of macroalgal overgrowth on reef fishes and means to reverse this condition have been little explored. An
experimental reduction of macroalgae was conducted at a site in the Watamu Marine National Park in Kenya, where a documented
increase in macroalgal cover has occurred over the last nine years. In four experimental 10 m by 10 m plots, macroalgae were
greatly reduced (fleshy algal cover reduced by 84%) by scrubbing and shearing, while four similar plots acted as controls.
The numerical abundance in all fish groups except wrasses and macroalgal-feeding parrotfishes (species in the genera Calotomus and Leptoscarus) increased in experimental algal reduction plots. Algal (Sargassum) and seagrass (Thalassia) assays, susceptible to scraping and excavating parrotfishes, were bitten more frequently in the algal reduction plots one
month after the manipulation. Further, surgeonfish (Acanthurus leucosternon and A. nigrofuscus) foraging intensity increased in these algal reduction plots. The abundance of triggerfishes increased significantly in experimental
plots relative to control plots, but densities remained low, and an index of sea urchin predation using tethered juvenile
and adult Echinometra mathaei showed no differences between treatments following macroalgal reduction. Dominance of reefs by macrofleshy algae appears
to reduce the abundance of fishes, mostly herbivores and their rates of herbivory, but also other groups such as predators
of invertebrates (triggerfishes, butterflyfishes and angelfishes).
The dominant protocol to study the effects of plant diversity on ecosystem functioning has involved synthetically assembled communities, in which the experimental design determines species composition. By contrast, the composition of naturally assembled communities is determined by environmental filters, species recruitment and dispersal, and other assembly processes. Consequently, natural communities and ecosystems can differ from synthetic systems in their reaction to changes in diversity. Removal experiments, in which the diversity of naturally assembled communities is manipulated by removing various components, complement synthetic-assemblage experiments in exploring the relationship between diversity and ecosystem functioning. Results of recent removal experiments suggest that they are more useful for understanding the ecosystem effects of local, nonrandom extinctions, changes in the natural abundance of species, and complex interspecific interactions. This makes removal experiments a promising avenue for progress in ecological theory and an important source of information for those involved in making land-use and conservation decisions.
Complex dynamic ecosystems are important natural capital assets. We investigate how Swedish national policy has approached these assets in its work on environmental indicators. In particular, we are interested in whether or not the indicators address ecosystem performance. We discuss our inventory of Swedish indicators in the context of ecosystem services, such as source and sink functions, and the capacity of ecosystems to sustain these functions for human well-being. We find that effective indicators have been developed to reflect energy and material flows within society and how human activities put pressure on the environment. The part of natural capital that concerns living systems is reflected in several of the Swedish indicators in a progressive fashion, but indicators that capture the dynamic capacity of ecosystems in sustaining the flow of source and sink functions need to be further developed. We provide examples of recent developments that have started to address such indicators in the context of ecosystem resilience and environmental change, and discuss directions for their further development. We stress the importance of monitoring ecosystem resilience and performance to avoid undesirable state shifts and building ecological knowledge and understanding of this capacity into environmental indicators and their associated management institutions.
Facing a human-dominated world, ecologists are now reconsidering the role of disturbance for coral reef ecosystem dynamics. Human activities alter the natural disturbance regimes of coral reefs by transforming pulse events into persistent disturbance or even chronic stress, by introducing new disturbance, or by suppressing or removing disturbance. Adding these alterations to natural disturbance regimes will probably result in unknown synergistic effects. Simultaneously, humans are altering the capacity of reefs to cope with disturbance (e.g. by habitat fragmentation and reduction of functional diversity), which further exacerbates the effects of altered disturbance regimes. A disturbance that previously triggered the renewal and development of reefs might, under such circumstances, become an obstacle to development. The implications of these changes for reef-associated human activities, such as fishing and tourism, can be substantial.
1. An understanding of the links between life histories and responses to exploitation could provide the basis for predicting shifts in community structure by identifying susceptible species and linking life‐history tactics with population dynamics.
2. We examined long‐term trends in the abundance of species in the North Sea bottom‐dwelling (demersal) fish community. Between 1925 & 1996 changes in species composition led to an increase in mean growth rate, while mean maximum size, age at maturity and size at maturity decreased. The demersal fish community was increasingly heavily fished during this period.
3. Trends in mean life‐history characteristics of the community were linked to trends in abundance of component species. An approach based on phylogenetic comparisons was used to examine the differential effects of fishing on individual species with contrasting life histories.
4. Those species that decreased in abundance relative to their nearest relative, matured later at a greater size, grew more slowly towards a greater maximum size and had lower rates of potential population increase. The phylogenetically based analyses demonstrated that trends in community structure could be predicted from the differential responses of related species to fishing.
5. This is the first study to link exploitation responses of an entire community to the life histories of individual species. The results demonstrate that fishing has greater effects on slower growing, larger species with later maturity and lower rates of potential population increase. The comparative approach provides a basis for predicting structural change in other exploited communities.
Myrica faya, an introduced actinorhizal nitrogen fixer, in invading young volcanic sites in Hawaii Volcanoes National Park. We examined the population biology of the invader and ecosystem-level consequences of its invasion in open-canopied forests resulting from volcanic cinder-fall. Although Myrica faya is nominally dioecious, both males and females produce large amounts of fruit that are utilized by a number of exotic and native birds, particularly the exotic Zosterops japonica. In areas of active colonization, Myrica seed rain under perch trees of the dominant native Metrosideros polymorpha ranged from 6 to 60 seeds mâ»Â² yrâ»Â¹; no seeds were captured in the open. Planted seeds of Myrica also germinated an established better under isolated individuals of Metrosideros than in the open. Diameter growth of Myrica is > 15-fold greater than that of Metrosideros, and the Myrica population is increasing rapidly. Rates of nitrogen fixation were measured using the acetylene reduction assay calibrated with ¹âµN. Myrica nodules reduced acetylene at between 5 and 20 μmol gâ»Â¹ hâ»Â¹, a rate that extrapolated to nitrogen fixation of 18 kg haâ»Â¹ in a densely colonized site. By comparison, all native sources of nitrogen fixation summed to 0.2 kg haâ»Â¹ yrâ»Â¹, and precipitation added < 4 kg haâ»Â¹ yrâ»Â¹. Measurements of litter decomposition and nitrogen release, soil nitrogen mineralization, and plant growth in bioassays all demonstrated that nitrogen fixed by Myrica becomes available to other organisms as well. We conclude that biological invasion by Myrica faya alters ecosystem-level properties in this young volcanic area; at least in this case, the demography and physiology of one species controls characteristics of a whole ecosystem.
Community ecology and ecosystem ecology seem to have existed in different worlds. Levin (1989) suggests that the gulf between the two is the consequence of the different historical traditions in each. Community ecology, for example, emerged from basic studies, where generalized patterns were sought in the natural interactions among the biota. From the outset, the goal has been to deduce general and simple theory. On the other hand, many of the modelling approaches developed to understand ecosystem dynamics emerged from specific applied problems, where not only biotic but abiotic and human disturbances transformed ecosystem function. That tradition, therefore, is often more complete, but at the price of producing a collection of complex specific examples from which generalization is difficult.
"Lake water quality and ecosystem services are normally maintained by several feedbacks. Among these are nutrient retention and humic production by wetlands, nutrient retention and woody habitat production by riparian forests, food web structures that cha nnel phosphorus to consumers rather than phytoplankton, and biogeochemical mechanisms that inhibit phosphorus recycling from sediments. In degraded lakes, these resilience mechanisms are replaced by new ones that connect lakes to larger, regional economi c and social systems. New controls that maintain degraded lakes include runoff from agricultural and urban areas, absence of wetlands and riparian forests, and changes in lake food webs and biogeochemistry that channel phosphorus to blooms of nuisance al gae. Economic analyses show that degraded lakes are significantly less valuable than normal lakes. Because of this difference in value, the economic benefits of restoring lakes could be used to create incentives for lake restoration."
A solid tumor is a cell population with extensive cellular heterogeneity, which severely complicates tumor treatment by therapeutic agents such as ionizing radiation. We model the response to ionizing radiation of a multicellular population whose cells have time-dependent stochastic radiosensitivity. A reaction-diffusion equation, obtained by assuming a random process with the radiation response of a cell partly determined by competition between repair and binary misrepair of DNA double-strand breaks, is used. By a suitable transformation, the equation is reduced to that of an Ornstein-Uhlenbeck process so explicit analytic solutions are available. Three consequences of the model's assumptions are that (1) response diversity within a population increases resistance to radiation, that is, the population surviving is greater than that anticipated from considering an average cell; (2) resistant cell subpopulations preferentially spared by the first part of a prolonged radiation protocol are driven biologically into more radiosensitive states as time increases, that is, resensitization occurs; (3) an inverse dose-rate effect, that is, an increase in cell killing as overall irradiation time is increased, occurs in those situations where resensitization dominates effects due to binary misrepair of repairable damage. The results are consistent with the classic results of Elkind and coworkers on extra cell killing attributed to cell-cycle redistribution and are in agreement with some recent results on in vitro and in vivo population radiosensitivity. They also generalize the therapeutic paradigm that low dose rate or fractionated radiation can help overcome hypoxic radioresistance in tumors.
Early cortical progenitor cells of the ventricular zone (VZ) differ from later progenitor cells of the subventricular zone (SVZ) in cell-type generation and their level of epidermal growth factor receptors (EGFRs). To determine whether differences in their behavior are causally related to EGFR number/density, we introduced extra EGFRs into VZ cells with a retrovirus in vivo and in vitro. This results in premature expression of traits characteristic of late SVZ progenitor cells, including migration patterns, differentiation into astrocytes, and proliferation of multipotential cells to form spheres. The choice between proliferation and differentiation depends on ligand concentration and progenitor cell age and may reflect different thresholds of stimulation. The level of EGFRs expressed by progenitor cells in the cortex may therefore contribute to the timing of their maturation and choice of response to pleiotropic environmental signals.