Article

Consequences of southern cassowary (Casuarius casuarius, L.) gut passage and deposition pattern on the germination of rainforest seeds

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

In Australia's tropical rainforests the endangered southern cassowary, Casuarius casuarius, L., is the largest native frugivore and many plant species, because of the size of their fruits or seeds, are thought to be largely dependent on cassowaries for their dispersal. In this study we asked whether the contribution of cassowaries to plant recruitment extends beyond removing seeds from the vicinity of the parent. To do this we conducted germination trials involving 17 rainforest plant species to test whether cassowary consumption and seed deposition pattern alter germination probability or time to germination. Twenty-four per cent of species showed changed germination probabilities, with one species showing no germination without cassowary consumption, and 35% showed changed time to germination. However these differences did not translate into any significant effects when considered across all species. We examined gut scarification, fruit pulp removal (de-inhibition) and deposition in faecal material as mechanisms for changing germination success; each contributed to the changed success of individual species. There was a negative effect of seed clumping on five species. We conclude that cassowary consumption can modify germination performance in a minority of rainforest plants and that the effect is generally positive. Although the effect on large seeded species was small it is most likely to be important as the cassowary is the only animal in Australia able to internally process large numbers of these seeds.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... In north-eastern Queensland, cassowaries consume the fruits of Schizomeria whitei, which are 2 -2.5 × 2.5 -3 cm when fresh (Cooper & Cooper 2004). Based on the locality, the bird involved is the Southern Cassowary, Casuarius casuarius (L., 1758), which also eats the purple drupes of another member of the Cunoniaceae, Davidsonia pruriens F. Muell., in northeastern Queensland (Bradford et al. 2008;Bradford & Westcott 2010;Cooper & Cooper 1994, 2004Crome 1976;Stocker & Irvine 1983). ...
... In north-eastern Queensland, cassowaries consume the fruits of Schizomeria whitei, which are 2 -2.5 × 2.5 -3 cm when fresh (Cooper & Cooper 2004). Based on the locality, the bird involved is the Southern Cassowary, Casuarius casuarius (L., 1758), which also eats the purple drupes of another member of the Cunoniaceae, Davidsonia pruriens F. Muell., in northeastern Queensland (Bradford et al. 2008;Bradford & Westcott 2010;Cooper & Cooper 1994, 2004Crome 1976;Stocker & Irvine 1983). ...
... As huge, solitary, forest-dwelling birds, cassowaries ingest fruits of various sizes, but especially relatively large ones (commonly 1.5 -6.5 cm diam.). Typically, these fruits fall from the canopy when ripe or are borne within 2 m of the ground, and they generally have a hard stone or seed(s) and pulpy outer layers, often, although not always, surrounded by a brightly coloured epicarp (Bradford et al. 2008;Crome 1976;Mack 1995;Pratt 1982;Stocker & Irvine 1983). Seed germination can be enhanced by passage through the gut (Lamothe et al. 1990;Bradford & Westcott 2010) and seeds are not regurgitated (Mack 1995). ...
Article
Schizomeria is a genus of forest trees or occasionally understorey shrubs represented by some seven species in New Guinea, one of which extends west to the Moluccas and two eastwards to the Solomon Islands; an additional two or three species occur in eastern Australia. In New Guinea, Schizomeria grows from lowland to subalpine forest, with most species occurring in the montane zone. This revision presents a key to the species, plus synonymy, descriptions, distribution maps, provisional conservation assessments and an index to collections for the taxa in New Guinea, the Moluccas and the Solomon Islands; local names are given in an Appendix. Species delimitation in New Guinea is not always straightforward and several taxa are quite variable, or have blurred boundaries, or both. Morphological characters that are useful in distinguishing among species include the type and distribution of the indumentum, the structure and position of the inflorescence (whether terminal, false-terminal or axillary) and the presence or absence of subspherical glands on the leaves. The flowers are polysymmetric, green, white or pale yellow, with small, 3-toothed petals; some species are andromonoecious. The subspherical or ellipsoidal drupes have a brown, orange, yellowish or whitish epicarp; they are dispersed by vertebrates, including cassowaries, fruit-bats and other arboreal frugivores including pigeons. The timber has some commercial value plus a number of local uses. Data for the Australian taxa are included in the discussions of dispersal and uses.
... Ground collection of fruit by flightless birds such as weka is likely to have been an important dispersal mechanism for many plant species, particularly those with larger fruits (Lee, Clout, Robertson, & Bastow Wilson, 1991;Thorsen, Seddon, & Dickinson, 2011). For example, in Australia, cassowaries (Casuarius spp.) and emus (Dromaius novaehollandiae) remove a significant proportion of seeds from the ground (Bradford & Westcott, 2010;Calviño-cancela et al., 2006). Lord (2002) speculated that seeds that were adapted for dispersal by flightless birds should fall to the ground when ripe and be conspicuous on the forest floor. ...
... This study is the first report of high levels of seed dispersal by a flightless bird in New Zealand. Cassowaries and emus are key seed dispersers for many plant species in Australia, consuming a wide variety of seeds and moving them large distances (e.g., Bradford & Westcott, 2010;Calviño-cancela et al., 2006). Taken together, these results suggest that ground removal of fruit by flightless birds may be or have been an important dispersal mechanism in other parts of the world. ...
Article
Full-text available
Understanding the mutualistic services provided by species is critical when considering both the consequences of their loss or the benefits of their reintroduction. Like many other Pacific islands, New Zealand seed dispersal networks have been changed by both significant losses of large frugivorous birds and the introduction of invasive mammals. These changes are particularly concerning when important dispersers remain unidentified. We tested the impact of frugivore declines and invasive seed predators on seed dispersal for an endemic tree, hinau Elaeocarpus dentatus, by comparing seed dispersal and predation rates on the mainland of New Zealand with offshore sanctuary islands with higher bird and lower mammal numbers. We used cameras and seed traps to measure predation and dispersal from the ground and canopy, respectively. We found that canopy fruit handling rates (an index of dispersal quantity) were poor even on island sanctuaries (only 14% of seeds captured below parent trees on islands had passed through a bird), which suggests that hinau may be adapted for ground‐based dispersal by flightless birds. Ground‐based dispersal of hinau was low on the New Zealand mainland compared to sanctuary islands (4% of seeds dispersed on the mainland vs. 76% dispersed on islands), due to low frugivore numbers. A flightless endemic rail (Gallirallus australis) conducted the majority of ground‐based fruit removal on islands. Despite being threatened, this rail is controversial in restoration projects because of its predatory impacts on native fauna. Our study demonstrates the importance of testing which species perform important mutualistic services, rather than simply relying on logical assumptions.
... Yet, the deinhibition process has not garnered sufficient attention when discussing the influences of digestion on seed germination. Most previous studies considered only the scarification effect in improving seed germination as they failed to test intact fruits (reviews in Samuels and Levey 2005;Robertson et al. 2006;Bradford and Westcott 2010). Our study distinguished the deinhibition effect A letter and asterisks indicate a significant difference between a treatment group and another group with the same letter within each respective species. ...
... No or extremely low proportions of germination in intact fruits were also noted in other fig species examined elsewhere (e.g., Lisci and Pacini 1994;Alves-Costa and Eterovick 2007;Bradford and Westcott 2010;Heer et al. 2010). Compared with depulped seeds, digestion by barbets decreased the germinability of F. superba from 45% to 5%. ...
Article
Full-text available
We investigated the frugivory of Taiwan Barbets (Megalaima nuchalis Gould, 1863) on passage time and germination of 19 species of commonly consumed fruits, distinguished the deinhibition and scarification effects, and tested if complete bird-gut passage increases seed germination. We measured fruit and seed size and seed retention times (SRTs) and examined the germination of intact fruits and pulp-removed and defecated seeds. Germination latency in intact fruits of most species was prolonged, whereas in more non-figs (7/12), the seed germinability increased after ingestion, and nearly all figs germinated by higher proportions after defecation or depulping. Yet, figs revealed major differences from non-figs. SRTs of both non-figs and figs were negatively dependent on fruit size, which was positively correlated to seed size in non-figs only. The germinability was negatively correlated and the germination onset time was positively correlated with SRTs of the last seeds in non-figs, but neither was correlated with SRTs in figs. Most (14/17) species with germination success were enhanced either by deinhibition and scarification, or the fruits hardly germinated but were aided by pulp removal. Deinhibition revealed greater effects than scarification in increasing the germinability and shortening latency, thus aiding, in particular, non-fig seeds with shorter SRTs or that are often culled during feeding.
... The present effects of historical shifts in species distribution across Australia are most evident for species from ancient lineages such as the Casuariidae, Macropodidae and Vombatidae 11 . The emu, Dromaius novaehollandiae, and cassowary species, Casuarius spp., are the last of the Casuariidae, -a family of flightless, large-bodied and predominately herbivorous birds [15][16][17] . The emu has a generalist omnivorous diet (mainly consuming plants 18,19 ), and is known to be an important non-standard dispersal agent (i.e. ...
Article
Full-text available
In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement. The emu, one of the last megafaunal species in Australia, has likely undergone substantial distribution changes, particularly near the east coast of Australia where urbanisation is extensive and some populations have declined. We modelled emu distribution across the continental mainland and across the Great Dividing Range region (GDR) of eastern Australia, under historical, present and future climates. We predicted shifts in emu distribution using ensemble modelling, hindcasting and forecasting distribution from current emu occurrence data. Emus have expanded their range northward into central Australia over the 6000 years modelled here. Areas west of the GDR have become more suitable since the mid-Holocene, which was unsuitable then due to high precipitation seasonality. However, the east coast of Australia has become climatically sub-optimal and will remain so for at least 50 years. The north east of NSW encompasses the range of the only listed endangered population, which now occurs at the margins of optimal climatic conditions for emus. Being at the fringe of suitable climatic conditions may put this population at higher risk of further decline from non-climatic anthropogenic disturbances e.g. depredation by introduced foxes and pigs. The limited scientific knowledge about wild emu ecology and biology currently available limits our ability to quantify these risks.
... In addition, our results suggest that an increase in frequency and intensity of drought, as predicted for the Australian Wet Tropics (Reisinger et al. 2014), may negatively affect fruit production of this palm species, with substantial ecological implications. For example, the reduced fruit availability may impact the Southern Cassowary, a keystone species that breeds in the period when Black Palms are usually fruiting, and disperses the Black Palm seeds thereby enhancing the species' germination rates (Bradford and Westcott 2010). One particularly interesting finding was the rapid recovery of fruiting activity of TFE palms in 2018. ...
Article
Aims Anthropogenic climate change is predicted to increase mean temperatures and rainfall seasonality. How tropical rainforest species will respond to this climate change remains uncertain. Here we analyzed the effects of a 4-year experimental throughfall exclusion on an Australian endemic palm (Normambya normanbyi) in the Daintree rainforest of North Queensland, Australia. We aimed to understand the impact of a simulated reduction in rainfall on the species’ physiological processes and fruiting phenology. Methods We examined the fruiting phenology and ecophysiology of this locally abundant palm to determine the ecological responses of the species to drought. Soil water availability was reduced overall by ~30% under a throughfall exclusion experiment (TFE), established in May 2015. We monitored monthly fruiting activity for 8 years in total (2009 - 2018), including four years prior to the onset of the TFE. In the most recent year of the study, we measured physiological parameters including photosynthetic rate, stomatal conductance and carbon stable isotopes (δ 13C, an integrated measure of water use efficiency) from young and mature leaves in both the dry and wet seasons. Important Findings We determined that the monthly fruiting activity of all palms was primarily driven by photoperiod, mean solar radiation and mean temperature. However, individuals exposed to lower soil moisture in the TFE decreased significantly in fruiting activity, photosynthetic rate and stomatal conductance. We found that these measures of physiological performance were affected by the TFE, season and the interaction of the two. Recovery of fruiting activity in the TFE palms was observed in 2018, when there was an increase in shallow soil moisture compared to previous years in the treatment. Our findings suggest that palms, such as the N. normanbyi, will be sensitive to future climate change with long-term monitoring recommended to determine population-scale impacts.
... Gut passage times can also influence seed dispersal distances (Corlett, 2009b). Seed vectors also differ in the amount and composition of the fecal material that is deposited with the seed, with consequences for seed fate that have rarely been investigated (e.g., Valenta and Fedigan, 2009;Bradford and Westcott, 2010). More comparisons between the post-dispersal fates of conspecific seeds dispersed by different vectors would be very valuable. ...
Article
Full-text available
Frugivory and seed dispersal have a crucial role to play in the novel landscapes that are emerging around the world. Robust predictions of what will happen when new combinations of fruits and frugivores meet are likely to require a more mechanistic understanding of frugivory and seed dispersal than we have at present, and one that does not focus solely on what eats and/or defecates what. This review summarizes what we know—and don’t know—at each stage from a frugivore deciding to eat fruit, through locating a fruit patch, selecting fruits within the patch, assessing their quality in the mouth and after ingestion, and dealing with the seeds. The major conclusion is that the functional diversity of frugivores (memory, senses, mouths, guts etc.) still limits our ability to make predictions. Key gaps in our understanding include the role of spatial memory in foraging, how (and at what stage) frugivores make the fine distinctions between fruits of differing nutrient contents that they appear capable of, the role of diet learning through linking post-ingestive feedback to pre-ingestive sensory cues, and the plant traits that influence seed fate during the processing of fruits. The efficiency of frugivory and seed dispersal in novel landscapes may not necessarily limit plant biomass, but it certainly limits plant diversity. Mitigation measures will require a better understanding of all the processes involved.Highlights► Summarizes what we know and don't know about the mechanisms of frugivory. ► Considers spatial memory, sensory cues, and post-ingestive feedback. ► Identifies key gaps in our current understanding.
... The effect of dispersal distance per se should also be evaluated in conjunction with the abiotic effects of origin and deposition sites. For example, a comparison between frugivore species with different dispersal distances but with similar microhabitat preferences for deposition sites would allow the study of dispersal distance in combination with the effects of origin and deposition sites on germination and plant recruitment ( Jordano et al., 2007;Bradford and Westcott, 2010). Transplant experiments like the one presented here are necessary to control some of the many potentially confounding factors that can complicate interpretation of comparative studies. ...
Article
Full-text available
The distribution and dynamics of plant populations depend on the recruitment of young individuals, which is influenced by seed production, animal seed dispersal, dispersal distance, and the deposition of seeds in favourable places for seed germination/establishment and seedling survival. In particular, seeds dispersed over long distances will likely encounter new environmental conditions that occur at large spatial scales, with seed and seedling survival influenced by the adaptation of plant populations to soil and climate conditions. In this paper, it is hypothesized that seed germination and seedling survival probabilities depend on seed origin and deposition sites. A reciprocal seed and seedling transplant experiment was carried out with zapote seeds (Manilkara zapota) to determine the effect of origin and deposition sites on seed germination and seedling survival over a year in the Greater Calakmul Region of Mexico. Two origin and two deposition sites were selected that show different soil moisture levels within the habitat of the Baird's tapir, a major seed disperser of M. zapota seeds. The results show that sites of origin and deposition influenced seed germination and seedling survival probabilities. This suggests that the displacement of seeds far from parent trees, while potentially reducing intraspecific competition, does not ensure their survival, and that seeds need to be deposited in microsites within their environmental tolerance for dispersal to be successful. Furthermore, this paper emphasizes the importance of field experiments to provide strong inference about the effects of environmental conditions on recruitment and distribution of plant species.
... Dispersal of seeds also depends on passage of viable seeds through the gut of potential dispersers (Wilson and Traveset 2000). Many studies have evaluated the effects of passage through the gut on seed germination with varying results, including increases in germination (Traveset 1998; Guerta et al. 2011; Hernández-Ladrón De Guevara et al. 2012), decreases in germination (Traveset et al. 2001; Verdú and Traveset 2004; Wilson and Downs 2012) and no effects on germination (Bradford and Westcott 2010; Pereira and Mourato 2012). ...
Article
Full-text available
Frugivorous seed-dispersers play an important role in the maintenance or regeneration of plant populations and communities. Greater Rheas are potentially one of the most import dispersers of seeds in South American grassland biomes owing to their capacity to swallow large seeds and their habitat of walking long distances each day. We studied the potential role of Greater Rheas in the dispersion of seeds of plants of the cerrado and caatinga grassland biomes through germination experiments. We evaluated the rate of seed germination and the mean time of germination of passage through the gut (seeds that passed through the digestive system of Rheas) compared with a control (seeds extracted directly from fruits). Nine species of plant from cerrado grasslands and three plant species from caatinga grasslands were tested. All three caatinga plant species germinated at a lower rate and took longer to germinate after passage through the gut, whereas two of nine cerrado plant species germinated at a higher rate and in less time after passage through the gut. Greater Rheas are probably good dispersers of some of the plant species we examined and may therefore be important in maintenance and regeneration of habitat. Future experiments will investigate the factors causing the variation in germination of seeds seen in this experiment.
... then voided the remainder of the toxic seeds intact. Ratites such as emus and cassowaries disperse large seeds in this way (e.g., Calvino-Cancela et al., 2006 ;Bradford and Westcott, 2010 ) and have been implicated in cycad dispersal, albeit infrequently and anecdotally ( White, 1912 ;Carter, 1923 ;Sargent, 1927 ; note that emus occur in M. miquelii habitat, but we never observed them). Extinct megafauna, such as Genyornis (a fl ightless bird that exceeded modern emus in size) probably had feeding behaviors similar to those of ratites, and their interactions with plants must have been considerable ( Murray and Vickers-Rich, 2004 ). ...
Article
Unlabelled: • Premise of the study: Plants that invest in large, heavy seeds and colorful, fleshy fruits or analogous structures seem adapted for dispersal by large vertebrates. Some such plants, like Australian cycads in the genus Macrozamia, do not disperse well, which could be explained by seed-dispersal relationships with megafauna that are rare or extinct in contemporary ecosystems. Such plants provide an opportunity to investigate the ecological consequences of low seed-dispersal distances. • Methods: We investigated seed dispersal of Macrozamia miquelii in Central Queensland by tracking the fate of marked seeds, identifying the dispersal fauna and quantifying population demography and spatial structure. • Key results: We found that 70-100% of marked seeds remained within 1 m of maternal females (cycads are dioecious). Of the 812 seeds recovered (from 840 originally marked) only 24 dispersed >1 m from maternal females, the greatest observed dispersal being 5 m. We found an average of 2.2 seedlings and 0.7 juveniles within 1.5 m of mature females, which suggests that most seeds that remain in the vicinity of maternal females perish. Within-stand densities ranged between 1000 and 5000 plants/ha. The brushtail possum Trichosurus vulpecula was the only animal observed to move the seeds. • Conclusions: Macrozamia are adapted for dispersal by megafauna that are rare or absent in contemporary ecosystems. We argue that Macrozamia are "grove forming" plants that derive ecological benefit from existing as high-density, spatially discrete populations, the function of megafaunal dispersal adaptations being the infrequent dispersal of seeds en masse to establish new such groves in the landscape.
... Two of the sixteen plant species (Croton sylvaticus and Sapium ellipticum) had between two and three seeds per fruit and/or fruit endocarp. Under such circumstances, the fruit and/or endocarp was considered a seed and only one germination event from each fruit and/or endocarp was recorded (Bradford and Westcott, 2010) and tallied to calculate the total germination for the pulped seed per plant species. The week from planting was used as a covariate when analysing the effects of seed treatment on germination probability. ...
Article
Full-text available
Frugivorous birds are among the most important consumers of fleshy fruits particularly in sub-tropical and tropical forest ecosystems. Whether or not such plant–frugivore interactions contribute to germination enhancement is still a subject of much debate. We tested the effect of gut treatment by four captive species of avian frugivores in comparison to manually depulped seeds and whole fruits on seedling emergence and germi- nation probability of seeds from sixteen plant species in South Africa. Moreover, we determined whether fruit weight of each plant species affected germination patterns. Across plant species, a total of 2795 seeds were planted, of which 50% germinated. Both seedling emergence and germination probability neither differed among the bird species nor in comparison to manually depulped seeds or whole fruits. Further, seedling emer- gence and germination probability were both unaffected by fruit weight. However, the germination probability of all treatments increased similarly with increasing number of weeks after planting. Overall, these results suggest that seed depulping, neither by gut treatment nor manually improved germination of seeds, irrespective of their fruit weights. Thus, the major contribution of frugivores to forest regeneration may be more confined in transporting seeds away from the mother plant than in germination enhancement per se.
... When dispersal is non-random in destination, the conditions experienced at deposition sites may predictably modify persistence (Schupp, Jordano & Gomez, 2010). Two examples are: vertebrate-dispersed seeds, which may be deposited with faecal material that can shorten or extend the time to germination depending on its chemical composition (Marambe, Nagaoka & Ando, 1993;Bradford & Westcott, 2010); and the deposition of seeds by watercourses into particular fluvial environments depending on the hydrodynamics and seed morphology (Merritt & Wohl, 2002). ...
Article
Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long-term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed-bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance-exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments.
... The relatively long gut passage time and ability to move large distances in search of food result in large dispersal distances for plants in its diet (Mack 1995; Westcott et al. 2005). Despite the cassowary's relatively gentle gut processing of seeds, it has been shown to alter the germination success of individual seeds of some plant species (Lamothe et al. 1990; Webber & Woodrow 2005; Bradford & Westcott 2010 ...
Article
Post-dispersal predation is a potentially significant modifier of the distribution of recruiting plants and an often unmeasured determinant of the effectiveness of a frugivore's dispersal service. In the wet tropical forests of Australia and New Guinea, the cassowary provides a large volume, long distance dispersal service incorporating beneficial gut processing; however, the resultant clumped deposition might expose seeds to elevated mortality. We examined the contribution of post-dispersal seed predation to cassowary dispersal effectiveness by monitoring the fate of 11 species in southern cassowary (Casuarius casuarius johnsonii Linnaeus) droppings over a period of 1 year. Across all species, the rate of predation and removal was relatively slow. After 1 month, 70% of seeds remained intact and outwardly viable, while the number fell to 38% after 1 year. The proportion of seeds remaining intact in droppings varied considerably between species: soft-seeded and large-seeded species were more likely to escape removal and predation. Importantly, across all species, seeds in droppings were no more likely to be predated than those left undispersed under the parent tree. We speculate that seed predating and scatter-hoarding rodents are responsible for the vast majority of predation and removal from droppings and that the few seeds which undergo secondary dispersal survive to germination. Our findings reinforce the conclusion that the cassowary is an important seed disperser; however, dispersal effectiveness for particular plant species can be reduced by massive post-dispersal seed mortality.
... C. radicalis and L. microcarya were found most frequently in the dung (Stocker & Irvine, 1983). Bradford and Westcott (2010) also reported that all Normanbya normanbyi seeds germinated after passing through a cassowary's gut compared to 80% germination of control seeds. ...
Article
Full-text available
LATIFAH, D., CONGDON, R. A. & HOLTUM, J. A. 2016. Regeneration strategies of palms (Arecaceae) in response to cyclonic disturbances. Reinwardtia 15 (1): 43 ? 59. — Tropical cyclones may act as important ecological drivers in northern Australia including north Queensland, as several cyclones impact this region each year between November and May. Extensive research has been conducted to investigate how regeneration of rainforest plant communities respond to frequent cyclonic disturbances. However, there have been few such studies on palms although they are important components of many rainforests. This research aimed to investigate the effects of canopy gaps following cyclonic disturbance (case study: Cyclone Larry) on regeneration of Arenga australasica (H. Wendl. & Drude) S. T. Blake ex H. E. Moore, Calamus australis Mart., C. moti F. M. Bailey, Hydriastele wendlandiana (F. Muell.) H. Wendl. & Drude and Licuala ramsayi var. ramsayi (F. Muell.) H. Wendl. & Drude. The field research was carried out at five sites in three areas located in northern Queensland: Tam O’Shanter/Djiru National Park, Clump Mountain National Park and Kurrimine Beach Conservation Park. Observations were made of recruitment, growth rate, leaf turnover and life history. We found that responses of palm regeneration following cyclonic disturbance varied among study sites; however, the recruitment of several species was favoured in gaps created by cyclones. The results also provide information on the various stages in the life cycle of the study palms.
... Mechanical and chemical abrasion of the seed coat can enhance seed germination potential, known as the scarification effect (Traveset, 1998;Traveset et al., 2007). Experimental studies have shown that the positive effect of gut passage on seed germination is more likely to be a result of deinhibition than scarification (Bradford & Westcott, 2010;Chang, Lee, Kuo, & Chen, 2012;Reid & Armesto, 2011). The inherent deposition of seeds in the faecal matrix by gorillas may also be beneficial because faeces provide minerals and moisture for the seed (Traveset, Bermejo, & Willson, 2001;Traveset et al., 2007). ...
Article
Full-text available
The quantitative and qualitative aspects of seed dispersal by the western lowland gorilla (Gorilla gorilla gorilla) were investigated in Gabon. Fresh faeces were collected and washed to identify and count the seeds. Seed germinability after gut passage was estimated with trials in a nursery at the study site. To assess the impact of gut passage on germination success and delay, comparative trials were run with four treatments: (i) gut passed seeds cleaned of faeces, (ii) gut passed seeds within a faecal matrix, (iii) seeds from fresh fruits surrounded by pulp, and (iv) seeds from fresh fruits cleaned of pulp. The analysis of 180 faecal units resulted in the identification of 58 species of seed. Germination trials were realized for 55 species and the mean germination success reached 46%. The impact of gut passage was investigated for Santiria trimera and Chrysophyllum lacourtianum; both species displayed higher germination success after ingestion. This study shows that gorillas effectively disperse seeds of numerous plant species, many of which provide timber or nontimber forest products or are typical of Gabonese forests. Considering the high-quality of gorilla deposition sites, gorillas is thought to play a unique role in the dynamics of Central African forest.
... Despite the unsolved puzzle of slow germination times, the remaining dispersal syndrome (early abscission, low contemporary dispersal rates, and visibility on the forest floor) of Elaeocarpus fruits suggest that they may be adapted for dispersal by flightless birds with less destructive gizzards [32,67]. For example, in Australia Elaeocarpus species are dispersed by cassowaries [68]. Flightless birds made up a significant proportion of the New Zealand avifauna [69], and the seed dispersal services these taxa provide are still largely unknown. ...
Article
Full-text available
Often the mutualistic roles of extinct species are inferred based on plausible assumptions, but sometimes palaeoecological evidence can overturn such inferences. We present an example from New Zealand, where it has been widely assumed that some of the largest-seeded plants were dispersed by the giant extinct herbivorous moa (Dinornithiformes). The presence of large seeds in preserved moa gizzard contents supported this hypothesis, and five slow-germinating plant species (Elaeocarpus dentatus, E. hookerianus, Prumnopitys ferruginea, P. taxifolia, Vitex lucens) with thick seedcoats prompted speculation about whether these plants were adapted for moa dispersal. However, we demonstrate that all these assumptions are incorrect. While large seeds were present in 48% of moa gizzards analysed, analysis of 152 moa coprolites (subfossil faeces) revealed a very fine-grained consistency unparalleled in extant herbivores, with no intact seeds larger than 3.3 mm diameter. Secondly, prolonged experimental mechanical scarification of E. dentatus and P. ferruginea seeds did not reduce time to germination, providing no experimental support for the hypothesis that present-day slow germination results from the loss of scarification in moa guts. Paradoxically, although moa were New Zealand's largest native herbivores, the only seeds to survive moa gut passage intact were those of small-seeded herbs and shrubs.
... The southern cassowary is endemic to the tropical rainforests of New Guinea and Australia [8,9]. It has a solitary nature [10] and a preference for dense forested habitats [11], hence relatively little is known about cassowary ecology in comparison to its extant relatives [12]. These gaps in knowledge extend to the phenotype: poorly studied structures in the cassowary include the syrinx, hyoid and larynx, despite morphological and comparative analyses of these structures in other palaeognaths, and their importance for primary biological functions and potentially phylogenetic inferences. ...
Article
Full-text available
Background: Palaeognathae is a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius, for which information on the skeletal systems of the syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. Results: The morphology of the syrinx, hyoid and larynx of C. casuarius is described from CT scans. The syrinx is of the simple tracheo-bronchial syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. Conclusion: Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies.
... The southern cassowary is endemic to the tropical rainforests of New Guinea and Australia [8,9]. It has a solitary nature [10] and a preference for dense forested habitats [11], hence relatively little is known about cassowary ecology in comparison to its extant relatives [12]. These gaps in knowledge extend to the phenotype: poorly studied structures in the cassowary include the syrinx, hyoid and larynx, despite morphological and comparative analyses of these structures in other palaeognaths, and their importance for primary biological functions and potentially phylogenetic inferences. ...
Preprint
Full-text available
Background: The Palaeognathae are a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius, for which information on the skeletal systems of the syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. Results: The morphology of the syrinx, hyoid and larynx of C. casuarius is described from CT scans. The syrinx is of the simple tracheo-bronchial syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. Conclusion: Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies. Key Words: Palaeognathae, Cassowary, Syrinx, Hyoid, Larynx, Morphology, Phylogenetics, Optimisation
Article
Full-text available
Cassowaries are important seed dispersers in tropical rainforests of New Guinea, but little is known about their population ecology or their responses to human disturbance. We used camera traps to measure the occurrence, local abundance, and activity patterns of northern cassowaries Casuarius unappendiculatus in lowland forests near Nimbokrang, Papua, and dwarf cassowaries Casuarius bennetti in the Arfak Mountains, West Papua. Our goals were to assess human impacts on cassowaries at multiple spatial scales and to measure their activity patterns over an elevational divide. At fine spatial scales local abundance of cassowaries was strongly reduced in areas frequented by humans. At larger spatial scales the distance to the nearest village or drivable road did not affect local abundance but altered the stage structure of the individuals detected, with a higher proportion of juveniles relative to adults. Local abundance of cassowaries was unrelated to site usage by introduced pigs. Both populations studied were strongly diurnal and their activity patterns were not significantly different. Efforts to control hunting remain critical to sustaining cassowaries and the seed dispersal services they provide.
Article
An apparent contradiction in the ecology of cycad plants is that their seeds are known to be highly poisonous, and yet they seem well adapted for seed dispersal by animals, as shown by their visually conspicuous seed cones and large seeds presented within a brightly colored fleshy "fruit" of sarcotesta. We tested if this sarcotesta could function as a reward for cycad seed dispersal fauna, by establishing if the toxic compound cycasin, known from the seeds, is absent from the sarcotesta. The Australian cycads Macrozamia miquelii and Cycas ophiolitica were tested (N = 10 individuals per species) using gas chromatography / mass spectrometry. Cycasin was detected at 0.34 % (fresh weight) in seed endosperm of M. miquelii and 0.28 % (fresh weight) in seed endosperm of C. ophiolitica. Cycasin was absent from the sarcotesta of the same propagules (none detected in the case of M. miquelii, and trace quantities detected in sarcotesta of only four of the ten C. ophiolitica propagules). This laboratory finding was supported by field observations of native animals eating the sarcotesta of these cycads but discarding the toxic seed intact. These results suggest cycads are adapted for dispersal fauna capable of swallowing the large, heavy propagules whole, digesting the non-toxic sarcotesta flesh internally, and then voiding the toxic seed intact. Megafauna species such as extant emus or cassowaries, or extinct Pleistocene megafauna such as Genyornis, are plausible candidates for such dispersal. Cycads are an ancient lineage, and the possible antiquity of their megafaunal seed dispersal adaptations are discussed.
Article
Full-text available
Tropical cyclones may act as important ecological drivers in northern Australia including north Queensland, as several cyclones impact this region each year between November and May. Extensive research has been conducted to investigate how the population structure of rainforest species respond to cyclonic disturbances. However, there have been few such studies on palms although they are important components of rainforests. Therefore, these study aimed to investigate how the population structure of Arenga australasica (H. Wendl. & Drude) S. T. Blake ex H. E. Moore, Calamus australis Mart., C. moti F. M. Bailey, Hydriastele wendlandiana (F. Muell.) H. Wendl. & Drude and Licuala ramsayi var. ramsayi (F. Muell.) H. Wendl. & Drude responded to a cyclone, as shown by size class reflecting mass recruitment after a periodic major disturbance (case study: Cyclone Larry). The field research was carried out in three study sites: Tam OShanter/Djiru National Park, Clump Mountain National Park and Kurrimine Beach Conservation Park located near Mission Beach and Kurrimine Beach, in north Queensland. Observations were made of life stage distribution, height and dbh distribution and wind resistance. We found that responses of the population structures of these rainforest palms varied following cyclonic disturbance by demonstrating higher densities of seedlings and juveniles, suggesting populations would be retained. More seedlings of C. australis and C. moti were found in gaps with higher canopy openness; oppositely, less seedlings of L. ramsayi were encountered under sites with lower sunlight. © 2017, Society for Indonesian Biodiversity. All rights reserved.
Article
The passage of seeds through an animal's gut can improve the probability of germination for some plants. We followed 13 Bornean orangutans (Pongo pygmaeus wurmbii) in a peatland forest in the Sabangau Forest, Central Kalimantan and collected their faecal samples opportunistically. From these samples, we identified 13 angiosperm species' seed, which ranged from small (0.61 ± 0.10 cm) to moderately large (2.16 ± 0.24 cm) seeds. We compared the germinability of the seeds of five species that were defecated by orangutans with conspecific seeds that were manually extracted from fruits and those from whole (intact) fruits, with the aim to test for effects of gut passage on germination. Overall germination success increased and the time taken to obtain 50% germination reduced as a result of interactions with orangutans in all species except Elaeocarpus mastersii. There was no germination success for three species (Nephelium maingayi, Diospyros areolata and Sandoricum beccarianum) from unhandled fruits during the 60-day trial period, and the remaining two species both had less than 100% germination. For all species, except Campnosperma coriaceum, the total germination fraction was substantially higher for manually extracted seeds than for defecated seeds. From these experiments, we concluded that while orangutans may not enhance germinability via ingestion and defecation, these large-bodied frugivores are functional dispersers for many plant species via their long-distance movements. Furthermore, the increased germinability of manually extracted seeds suggests that spitting of seeds by foraging orangutans could be of unrecognized importance in the demography of peat forest plants. © 2017 The Linnean Society of London, Biological Journal of the Linnean Society.
Article
Full-text available
Frugivorous seed-dispersers play an important role in the maintenance or regeneration of plant populations and communities. Greater Rheas are potentially one of the most import dispersers of seeds in South American grassland biomes owing to their capacity to swallow large seeds and their habitat of walking long distances each day. We studied the potential role of Greater Rheas in the dispersion of seeds of plants of the cerrado and caatinga grassland biomes through germination experiments. We evaluated the rate of seed germination and the mean time of germination of passage through the gut (seeds that passed through the digestive system of Rheas) compared with a control (seeds extracted directly from fruits). Nine species of plant from cerrado grasslands and three plant species from caatinga grasslands were tested. All three caatinga plant species germinated at a lower rate and took longer to germinate after passage through the gut, whereas two of nine cerrado plant species germinated at a higher rate and in less time after passage through the gut. Greater Rheas are probably good dispersers of some of the plant species we examined and may therefore be important in maintenance and regeneration of habitat. Future experiments will investigate the factors causing the variation in germination of seeds seen in this experiment.
Article
Full-text available
Long-distance dispersal of seeds is an important process for maintaining genetic connectivity between forest fragments and for promoting fast re-colonisation of deforested land. Based on the hypothesis that the Greater Rhea ( Rhea americana), a large flightless bird native to South America, could play a major role as a disperser of tree seeds, we evaluated whether passage of seeds through its digestive tract affected germination of six tree species native to central Argentina. We determined the proportion of seeds that germinated in a climate-controlled chamber for untreated ( control) seeds, as found under seeding trees, seeds that passed through the digestive tract of captive Greater Rheas, and seeds treated with optimum pre-germination treatments for seedling production. Our results showed that the germination response to passage through the gut reached or surpassed the optimum germination treatments in three species of tree, was similar to control treatments and lower than optimum treatments in two species, and lower than all alternative treatments in one species of tree. We conclude that Greater Rheas are one of the few remaining large-bodied native animals with potential to disperse seeds of large fruits effectively, thus reinforcing the importance of restoring former populations of Greater Rhea.
Article
Extant cassowaries (Casuarius) are unique flightless birds found in the tropics of Indo‐Australia. They have garnered substantial attention from anatomists with focus centered on the bony makeup and function of their conspicuous cranial casques, located dorsally above the orbits and neurocranium. The osteological patterning of the casque has been formally described previously; however, there are differing interpretations between authors. These variable descriptions suggest that an anatomical understanding of casque anatomy and its constituent elements may be enhanced by developmental studies aimed at further elucidating this bizarre structure. In the present study, we clarify casque osteology of the southern cassowary (C. casuarius) by detailing casque anatomy across an extensive growth series for the first time. We used micro‐computed tomography (μCT) imaging to visualize embryonic development and post‐hatching ontogeny through adulthood. We also sampled closely related emus (Dromaius novaehollandiae) and ostriches (Struthio camelus) to provide valuable comparative context. We found that southern cassowary casques are comprised of three paired (i.e., nasals, lacrimals, frontals) and two unpaired elements (i.e., mesethmoid, median casque element). Although lacrimals have rarely been considered as casque elements, the contribution to the casque structure was evident in μCT images. The median casque element has often been cited as a portion of the mesethmoid. However, through comparisons between immature C. casuarius and D. novaehollandiae we document the median casque element as a distinct unit from the mesethmoid. This article is protected by copyright. All rights reserved.
Article
Global positioning system (GPS) technology for tracking wildlife continues to evolve at a remarkable pace. As animal movement is increasingly recognised as being critical for several ecological processes, advanced telemetry technology permits collection of a high volume of data across short time intervals that was previously unobtainable. Here we describe the use of GPS telemetry to track the movements of five tagged Emus (Dromaius novaehollandiae Latham) released within the Jarrah (Eucalyptus marginata Sm.) forests of south-western Australia. The Emu plays a significant role as a seed disperser for many species. Describing the movement patterns of this species is a key requirement in refining the extent and significance of its contribution to seed dispersal, both locally and over long distances. We found that Emus followed a typical correlated random walk pattern and that each bird demonstrated a variable response to the landscape in terms of behaviour, extent of movement and habitat selection. From a methodological perspective, 50% of our devices detached before 30 days of GPS locations could be collected, reflecting a need for device refinement for future studies on large ratites. Nevertheless, our preliminary data provide useful insights into the movements of the Emu and potential impacts on seed dispersal within the Jarrah forests.
Article
Full-text available
Multi-seeded fleshy-fruits of Morus nigra and Solanum luteum were offered to two species of frugivorous birds, Pycnonotus xanthopygos and Turdus merula. The fruits were swallowed whole but the seeds were gradually defecated during a period of a few hours in numbers per feces significantly lower than those within the complete fruit. This pattern of temporal seed deposition might have a positive implication on seed dispersal in space. Different retention times of S. luteum seeds had no effect on their germination success, but as number of seeds per group increases their germination success decreases in both plant species. Therefore, in the case of multi-seeded fruits, bird ingestion plays an important role by reducing the number of seeds per group, which in turn may enhance germination. -from Authors
Article
Full-text available
Popular procedures to control the chance of making type I errors when multiple statistical tests are performed come at a high cost: a reduction in power. As the number of tests increases, power for an individual test may become unacceptably low. This is a consequence of minimizing the chance of making even a single type I error, which is the aim of, for instance, the Bonferroni and sequential Bonferroni procedures. An alternative approach, control of the false discovery rate (FDR), has recently been advocated for ecological studies. This approach aims at controlling the proportion of significant results that are in fact type I errors. Keeping the proportion of type I errors low among all significant results is a sensible, powerful, and easy-to-interpret way of addressing the multiple testing issue. To encourage practical use of the approach, in this note we illustrate how the proposed procedure works, we compare it to more traditional methods that control the familywise error rate, and we discuss some recent useful developments in FDR control.
Article
Full-text available
Seed and fruit size are important to rain forest trees because they limit what can disperse their seeds and they influence what type of defenses and nutrient reserves their seedlings will acquire, Where establishment conditions might favor larger seeds, maximum seed size can be constrained by disperser size. Because the Paleotropics have larger frugivores than the Neotropics, I predicted more large fruits would be found in the Paleotropics. In eight pantropicai, endozoochorous plant families, the Old World representatives tended to have more taxa with larger fruits than the New World representatives. In all families the mean and range of fruit sizes were greater in the Old World, which suggests that the evolution of large fruits and seeds might be more tightly constrained in the Neotropics owing to the relative scarcity of large frugivores there.
Article
Full-text available
The rare Australian rainforest tree Ryparosa sp. nov. 1 aff. javanica (sensu Webber & Curtis, BW-017; Achariaceae) has large fleshy fruits that undergo a distinctive colour change during ripening. Fruit seem highly suited to frugivore interactions with large ground-dwelling avian or marsupial frugivores, a role primarily filled by the endangered cassowary. We found that fruits had chemical defence traits that closely paralleled morphological ripening signals. Young fruit seeds had amongst the highest concentrations of plant tissue cyanogens ever recorded (some in excess of 12 mg g–1 dw), yet the flesh of ripe fruits had negligible cyanogen defence. A seed treatment trial found that cassowary gut passage significantly improved germination from 4% to 92%, and we were not able to replicate this result with simulated treatments. While high levels of fruit fly larval infestation accounted for reduced seed viability, this predation was apparently reduced by cassowary gut passage. Post-germination seedling traits such as haustorial cryptocotylar cotyledons and epigeal germination may increase the chance of survival for establishing seedlings. We conclude that the range of traits seen in Ryparosa recruitment is particularly suited to interactions with frugivores and survival in a rainforest ecosystem.
Article
Full-text available
The importance of the first mechanism and the modification of seed coat traits (e.g., permeability of the coat to water and gases) after gut treatment, which changes the capacity of germination and/or the speed at which seeds germinate, were studied. The overall effect of gut treatment on seed germination percentage was significantly positive (mean effect size lnOR=0.29; 95% CI: (0.27-0.31)). A similar value was found when meta-analysis was carried out at the study level (lnOR=0.25; (0.23-0.72)), which avoids pseudo-replication effects. The heterogeneity test of Qt was highly significant (P<0.00001), implying that other variables (predictors) account for some of the variation among studies. It is suggested that seed passage through the gut of a vertebrate can probably break only seed coat dormancy (functional dormancy) and not physiological (internal or embryological) dormancy, as difference in germination rate between ingested and uningested seeds are usually only a few days and more rarely a few weeks.
Chapter
Full-text available
The chapters of this book on seed dispersal are divided into four parts: (1) frugivores and frugivory (8 chapters); (2) seed and seedling shadows (7 chapters); (3) seed fate and establishment (eight chapters); and (4) management implications and conservation (six chapters). The book presents both recent advances and reviews of current knowledge.
Article
Full-text available
Dormant seeds of a California chaparral annual were induced to germinate by smoke or vapors emitted from smoke-treated sand or paper. Nitrogen oxides induced 100 percent germination in a manner similar to smoke. Smoke-treated water samples inducing germination were comparable in acidity and concentration of nitrate and nitrite to nitrogen dioxide (NO2)–treated samples. Vapors from smoke-treated and NO2-treated filter paper had comparable NO2flux rates. Chaparral wildfires generate sufficient nitrogen oxides from combustion of organic matter or from postfire biogenic nitrification to trigger germination of Emmenanthe penduliflora. Nitrogen oxide–triggered germination is not the result of changes in imbibition, as is the case with heat-stimulated seeds.
Article
Full-text available
The germination of seven common weeds and seven species native to south-western Australia was studied at three sites where they co-occur and in the laboratory. Under field conditions, final germination of the exotic species was much higher than that of the native species, and the number of days to reach 50 % final germination was lower. For some of the germination period, soil moisture was lower than expected after 48 h without rain, with one dry period lasting 10 d. Overall, germination rose with increasing wetness of the three sites, especially among the weeds. Most exotic species germinated under laboratory conditions needed less than 10 d to reach 50 % of final germination which was further delayed by 2 d when seeds were removed from their moist substrate and allowed to dry out (air-drying) for 48 h. Most native species took 10–35 d, with a mean delay of 7 d after 48 h of air-drying. Total germination of the weeds was close to 100 % and was little affected by periods of air-drying. Germination of the native species was more variable and greatly reduced by air-drying in two species. We conclude that water availability as it varies through time and space is significant in controlling germination even during the wet season. The quicker and greater responses of weed seeds to moisture may contribute toward the superior ability of weeds to colonise disturbed habitats. Differences in life form, seed size, flatness, presence of appendages, and ability to absorb or retain water only partially explain these results. © 2000 Éditions scientifiques et médicales Elsevier SAS
Article
Full-text available
The capacity of seeds to germinate after ingestion by frugivores is important for the population dynamics of some plant species and significant for the evolution of plant-frugivore interactions. In this paper the effects of different vertebrates on seed germination of nearly 200 plant species are reviewed, searching for patterns that predict the circumstances in which germination of seeds is enhanced, inhibited, or unaffected by the passage through the digestive tract of a seed disperser. It was found that seed dispersers commonly have an effect on the germinability of seeds, or on the rate of germination, or both, in about 50% of the plants they consume, although the diversity of animal species tested so far is still rather low (42 bird species, 28 non-flying mammals, 10–15 bats, 12 reptiles, 2 fishes). Enhancement of germination occurred about twice as often as inhibition.
Article
Full-text available
Coevolutionary models of the interactions between fruiting plants and avian seed dispersers have been influenced by the assumption that regurgitation and defecation of seeds have diffferent effects on seed coats, and consequently seed germination. We evaluated how the manner of seed processing affects seed germination by feeding fruits of three bird-dispersed shrubs, spicebush (Lindera benzoin), chokecherry (Prunus virginiana), and arrowwood (Viburnum dentatum), to captive cedar waxwings (Bombycilla cedrorum) and thrushes (Turdus migratorius, Hylocichla mustelina, Catharus guttatus and C. minimus). Cedar waxwings defecate all seeds, whereas thrushes regurgitate most seeds. For all three shrub species and all five bird species, there were no differences in germination success between seeds manually cleaned of pulp, and cleaned, bird-passed seeds, regardless of whether seeds were regurgitated or defecated. However, seeds of Lindera and Prunus that were defecated by cedar waxwings and planted with feces, mimicking the depositional environment of defecated seeds in nature, suffered reduced germination relative to cleaned seeds. Thus, our results do not suggest that whether seeds are regurgitated or defecated is an important component of dispersal quality because of direct effects on the seed coat. Instead, seed processing modes differed in their effects on seed germination because of the feces associated with defecated seeds. Removal of fruit pulp from seeds by frugivores, a fundamental consequence of dispersal in animal guts, was critical for germination, especially for seeds within the lipid-rich fruits of Lindera and Viburnum. This suggests that for some fruiting plants, frugivores provide an essential service by freeing seeds from fruit pulp, in addition to their role in seed dispersal.
Article
Full-text available
Large frugivorous forest birds are among the most endangered avian groups in the Neotropics. Despite this fact, there has been little field work on members of these groups or on other large Neotropical forest birds. While current studies of Neotropical forests are beginning to provide data for reserve management at the ecosystem level, we lack information for management of particular species or habitats. Throughout Latin America, large forest frugivores are economically important as food, as pets or in local crafts. They can also be important seed dispersers and can be used as indicator species of habitat disturbance in protected areas. The conservation status of these birds demands more attention and commitment from conservation organizations and the scientific community in general. Further field research should focus on the basic ecology and natural history of endangered and non-endangered species. These studies will aid in developing badly needed long-term management and monitoring plans both for populations of large forest frugivores and their habitats.
Article
Full-text available
Approximately two-thirds (64%) of all dry season samples of elephant dung analysed during a 3-year study in the Main Camp subregion of Hwange National Park, Zimbabwe, contained seed and/or pod materials from Acacia erioloba. Most seeds were recovered intact and actively germinating seeds were not uncommon. Very little pod mass relative to seed mass was recovered in most instances, with pod fragments recorded from only 56% of all exhaustively sampled elephant dung piles containing A. erioloba fruit materials. Nonetheless, large pod fragments and even entire intact pods were recovered occasionally from elephant dung. Seeds and pods of A. erioloba may comprise 12% or more of total wet-weight dung mass; individual dung piles were found which contained > 5000 A. erioloba seeds. Birds and smaller mammals search out and consume A. erioloba seeds present within elephant dung piles. The findings of this study indicate that potential digestibility of A. erioloba seeds for bush elephants (Loxodonta africana africana) may be much higher than expected from previous studies. In controlled feeding trials with captive bush elephants (age 11–15 years old) maintained on predominantly free-range dry season diets, the estimated efficiency of digestion for A. erioloba seeds consumed in pods was 81% to 96%, with a gut-transit time of between 24.5 and 36.0 h. On the basis of throughput times determined in experimental feeding trials, potential elephant-dispersal distances of 20–50 km are predicted for A. erioloba in the Kalahari Sands landscapes of southern central Africa.
Article
Full-text available
Subsistence game bunting has profound negative effects on the species diversity, standing biomass, and size structure of vertebrate assemblages in Amazonian forests that otherwise remain largely undisturbed. These effects are likely to be considerably aggravated by forest fragmentation because fragments are more accessible to hunters, allow no (or very low rates of) recolonization from nonharvested source populations, and may provide a lower-quality resource base for the frugivore-granivore vertebrate fauna. I examined the likelihood of midsized to large-bodied bird and mammal populations persisting in Amazonian forest fragments of variable sizes whenever they continue to be harvested by subsistence hunters in the aftermath of isolation. I used data from a comprehensive compilation of game-harvest studies throughout Neotropical forests to estimate the degree to which different species and populations have been overharvested and then calculated the range of minimum forest areas required to maintain a sustainable harvest. The size distribution of 5564 Amazonian forest fragments-estimated from Landsat images of six regions of southern and eastern Brazilian Amazonia-clearly shows that these are predominantly small and rarely exceed 10 ha, suggesting that persistent overhunting is likely to drive most midsized to large vertebrate populations to local extinction in fragmented forest landscapes. Although experimental studies on this negative synergism remain largely unavailable, the prospect that increasingly fragmented Neotropical forest regions can retain their full assemblages of avian and mammalian species is unlikely.
Article
Full-text available
Tapirs (Tapiridae) are the last representatives of the Pleistocene megafauna of South and Central America. How they affect the ecology of plants was examined by studying the diversity, abundance, and condition of seeds defec-atedd by the lowland tapir (Tapirus terrestris) in Amazonian Brazil. Additionally, the spatio-temporal pattern of the seed-rain and seed-shadows generated by tapirs was recorded. Three hundred and fifty-six tapir faeces were examined. Eleven per cent were found in water (n = 41), while 88% were located on dry land (n = 315). Of those found on dry land, 84% were located at sites that flood seasonally, while 14% of the total were encountered at forest sites that do not flood. In 127 faeces checked in the laboratory over 12 906 seeds of at least 39 species were found. Seed viability ranged from 65% for Maximiliana maripa to 98% for Enterolobium schomburgkii. Of nine seed species planted in the laboratory, seven germinated within 4 wk, with one species achieving an 89% germination rate. For many species recruitment to the seedling stage was also high under natural conditions, with 13 plant species occurring as seedlings in older faeces. Tapir generated seed-rain occurred throughout the year, with seeds defecated in all months. Two temporal patterns in species seed rain occurred: (1) contiguous monthly occurrence with peaks in abundance, and (2) discontinuous occurrence (time clumped) with small (a few months) to large (many months to more than a year) temporal gaps. The highest diversity of seeds appeared in April, at the end of the dry season. As the last of the Pleistocene megafauna of the region, tapirs may have particular import-ance as dispersers of large seeds and generators of unique seed dispersion patterns.
Article
Full-text available
Summary 1. Seed germination characteristics are often modified after seeds are ingested by frugivores. Factors that are intrinsic either to the plant or to the frugivore's digestive tract are responsible for the great variation observed in germination response. 2. Our objectives were to determine whether and how the seed germination patterns of five common western Mediterranean plant species are affected by seed passage through the guts of their major dispersers, and to elucidate the mechanism by which such patterns are changed. 3. We used captive birds ( Turdus merula and Sylvia melanocephala ) to obtain ingested seeds and compared their germination rate (speed) and germinability (final percent germination) with those of controls (uningested, pulp-removed seeds), controlling for seed age, size and source. Germination was monitored for 2 years in an experimental garden. We evaluated the possible changes in seed traits after ingestion by measuring weight and coat thickness, and by observing seed coat sculpture. 4. Rate of seed germination, but not germinability, changed in all species after gut treatment. The greatest effect was in Osyris , in which germination was much enhanced. A great acceleration of germination, which is likely to translate into a seedling size advantage, was also found in Asparagus . In the other three species tested, germination was slower for ingested than for control seeds. 5. For Rubus and Rubia seeds, we found a different germination response depending upon the frugivore species tested. A different degree of seed coat scarification caused by differences in gut retention time, chemical and/or mechanical abrasion probably account for such responses. 6. In three of the species ( Osyris , Rubia and Phillyrea ), seed weight decreased after gut treatment. Such weight loss was not caused by any change in coat thickness, but may have been because of the scarification and consequent alteration of the seed coat structure. 7. The five Mediterranean species studied germinate when rains are most likely to fall (mostly autumn and spring). The different speed of germination promoted by gut treat- ment within frugivores may increase the probability that seeds can recruit successfully at a given time and in a given place. 8. This study suggests that frugivores contribute to the heterogeneity in germination characteristics not only within plant populations but also within plant communities, each frugivore species having a particular effect on the seeds of each plant consumed.
Article
Full-text available
To determine the sources of dispersed seeds I inserted unique tags in fallen Aglaia aff flavida seeds before dwarf cassowaries (Casuanus bennetti) ate the fruits containing the seeds Thirty naturally-dispersed, marked seeds were re-located in cassowary droppings m a 400 ha study area The distribution of seed dispersal distances did not differ significantly from a normal distribution with a mean dispersal distance of 388 m, SD= 196 8 Mean distance of dispersed seeds to nearest mature conspecific tree was 170 m, SD= 108 4, dispersed seeds usually landed closer to other conspecifics than their parent The estimated distribution of all seeds (including many undispersed seeds) was leptokurtic, creating high densities near source trees (>0 035 seeds m-2 within 100 m of bole) that quickly tapered off (<0 002 seeds m-2 > 100 m from the bole), any density dependent effects are liable to be manifest only near parent trees Cassowary movement patterns and resting behavior caused non-random dispersal of seeds Seeds were preferentially moved to level sites uphill from their source trees along routes that did not cross.steep terrain Undispersed seeds generally landed downhill from source trees This population of Aglaia would probably contract downhill into smaller, fragmented populations m the absence of cassowary-mediated dispersal
Article
Full-text available
The probability of interspecific seedling competition from bird droppings is high because fruit-eating birds, on average, deposit more than two species in a single dropping. Moreover, birds vary both in the number of plant species they deposit in a given dropping and in the seed composition of those droppings. In a preliminary experiment, I examined effects of interspecific seedling competition from seeds found in bird droppings. Certain plant species were competitively superior in pairwise growth experiments using six common second-growth species. The survival of certain shrubs depended on which species it was disseminated with in bird droppings. Rapid germination time may promote competitive superiority in some cases. Birds affect plant fitness not only because of their behavior following dispersal, but also because they deposit seeds in different densities and combinations.
Article
Full-text available
Seed dispersal links the end of the reproductive cycle of adult plants with the establishment of their offspring, and is widely accepted to have a profound effect on vegetation structure. Confirming and quantifying this effect, however, has proven to be a challenge. Recent research on animal-mediated seed dispersal has brought us closer to this goal: ecologists have been explicitly examining the processes that mediate seed deposition and seedling recruitment. Exciting new techniques, such as the analysis of stable isotope ratios and molecular genetic markers, are making it possible to relate dispersed seeds and seedlings back to parent plants. Meanwhile, evidence from plant demography research is revealing that seed dispersal might have an important role in determining patterns of tree diversity and distribution. The continued synergy between seed dispersal research and the study of plant demography should help researchers link seed dispersal and adult vegetation structure, closing the seed dispersal loop.
Article
Full-text available
The chapters of this book on seed dispersal are divided into four parts: (1) frugivores and frugivory (8 chapters); (2) seed and seedling shadows (7 chapters); (3) seed fate and establishment (eight chapters); and (4) management implications and conservation (six chapters). The book presents both recent advances and reviews of current knowledge.
Article
Full-text available
Seeds dispersed by tropical, arboreal mammals are usually deposited singly and without dung or in clumps of fecal material. After dispersal through defecation by mammals, most seeds are secondarily dispersed by dung beetles or consumed by rodents. These post-dispersal, plant-animal interactions are likely to interact themselves, as seeds buried by dung beetles are less likely to be found by rodents than unburied seeds. In a series of three experiments with seeds of 15 species in central Amazonia (Brazil), we determined (1) how presence and amount of dung associated with seeds influences long-term seed fate and seedling establishment, (2) how deeply dung beetles bury seeds and how burial depth affects seedling establishment, and (3) how seed size affects the interaction between seeds, dung beetles, and rodents. Our overall goal was to understand how post-dispersal plant-animal interactions determine the link between primary seed dispersal and seedling establishment. On average, 43% of seeds surrounded by dung were buried by dung beetles, compared to 0% of seeds not surrounded by dung ( n=2,156). Seeds in dung, however, tended to be more prone than bare seeds to predation by rodents. Of seeds in dung, probability of burial was negatively related to seed size and positively related to amount of dung. Burial of seeds decreased the probability of seed predation by rodents three-fold, and increased the probability of seedling establishment two-fold. Mean burial depth was 4 cm (0.5-20 cm) and was not related to seed size, contrary to previous studies. Probability of seedling establishment was negatively correlated with burial depth and not related to seed size at 5 or 10 cm depths. These results illustrate a complex web of interactions among dung beetles, rodents, and dispersed seeds. These interactions affect the probability of seedling establishment and are themselves strongly tied to how seeds are deposited by primary dispersers. More generally, our results emphasize the importance of looking beyond a single type of plant-animal interaction (e.g., seed dispersal or seed predation) to incorporate potential effects of interacting interactions.
Article
Full-text available
The processes determining where seeds fall relative to their parent plant influence the spatial structure and dynamics of plant populations and communities. For animal dispersed species the factors influencing seed shadows are poorly understood. In this paper we test the hypothesis that the daily temporal distribution of disperser behaviours, for example, foraging and movement, influences dispersal outcomes, in particular the shape and scale of dispersal curves. To do this, we describe frugivory and the dispersal curves produced by the southern cassowary, Casuarius casuarius, the only large-bodied disperser in Australia's rainforests. We found C. casuarius consumed fruits of 238 species and of all fleshy-fruit types. In feeding trials, seeds of 11 species were retained on average for 309 min (+/-256 SD). Sampling radio-telemetry data randomly, that is, assuming foraging occurs at random times during the day, gives an estimated average dispersal distance of 239 m (+/-207 SD) for seeds consumed by C. casuarius. Approximately 4% of seeds were dispersed further than 1,000 m. However, observation of wild birds indicated that foraging and movement occur more frequently early and late in the day. Seeds consumed early in the day were estimated to receive dispersal distances 1.4 times the 'random' average estimate, while afternoon consumed seeds received estimated mean dispersal distances of 0.46 times the 'random' estimate. Sampling movement data according to the daily distribution of C. casuarius foraging gives an estimated mean dispersal distance of 337 m (+/-194 SD). Most animals' behaviour has a non-random temporal distribution. Consequently such effects should be common and need to be incorporated into seed shadow estimation. Our results point to dispersal curves being an emergent property of the plant-disperser interaction rather than being a property of a plant or species.
Article
To determine the sources of dispersed seeds I inserted unique tags in fallen Aglaia aff. flavida seeds before dwarf cassowaries (Casuarius bennetti) ate the fruits containing the seeds. Thirty naturally-dispersitd. marked seeds were re-located in cassowary droppings in a 100 ha study area. The distribution of seed dispersal distances did not differ significantly from a normal distribution with a mean dispersal distance of 388 m, SD=196.8. Mean distance of dispersed seeds to nearest mature conspecific tree was 170 m, SD=108.4: dispersed seeds usually landed closer to other conspecifics than their parent. The estimated distribution of all seeds (including many undispersed seeds) was leptokurtic, creating high densities near source trees (>0.035 seeds m(-2) within 100 m of bole) that quickly tapered off (<0.002 seeds m(-2) >100 m from the bole); any density dependent effects are liable to be manifest only near parent trees. Cassowary movement patterns and resting behavior caused non-random dispersal of seeds. Seeds were preferentially moved to level sites uphill from their source trees along routes that did not cross steep terrain, Undispersed seeds generally landed downhill from source trees. This population of Aglaia would probably contract downhill into smaller, fragmented populations in the absence of cassowary-mediated dispersal.
Article
IntroductionFruits of Australia's rainforestsFrugivores of Australia's rainforestsIs Australia different?Seed dispersal in Australia's rainforestsSummaryReferences
Article
This book provides information on the historical and theoretical perspectives of biodiversity and ecology in tropical forests, plant and animal behaviour towards seed dispersal and plant-animal interactions within forest communities, consequences of seed dispersal, and conservation, biodiversity and management.
Article
Casuarius casuarius inhabits the rainforests of northeastern Australia and some of the islands to the north. It depends on fruit which has fallen from the middle and upper forest canopy. During the two-year study period diaspores of 78 plant species were found in cassowary dung. Although the germination percentage of seeds in dung were variable, some germination was observed for 70 species. The passage of most diaspores through a cassowary does not appear to greatly affect seed germination characteristics. These birds are the only extant frugivores large enough to effectively disperse many of the plant species found in the rainforests of this region.
Article
Many studies of post-dispersal seed predation have focused on density and distance dependent mortality, while relatively few have examined the fates of isolated seeds. Yet, scatter-dispersed seeds (sensu Howe) are commonly deposited singly or in small groups. Furthermore, even in species with highly aggregated seed distributions, the fates of the most widely dispersed individuals may be critical for recruitment. We compared predation rates on single, isolated seeds, among 40 species of trees in lowland tropical rain forest at Gunung Palung, West Kalimantan, Indonesia. Seeds were placed along four replicate transects and monitored for damage by predators, removal and germination in four trials, each lasting at least 30 days. Tethering of seeds did not affect removal rates, indicating that removals were attributable to seed predators and not merely to physical disturbance by animals or abiotic factors. After 30 days, mortality due to seed predation, averaged over species, was more than 50%; among species, predation losses ranged from 0 to 100%. Over the range of seed sizes we examined (0.1 g to 11.6 g fresh weight) predation rates were negatively associated with seed size and with the thickness and hardness of the seed coat. Lower predation on larger seeds is contrary to theoretical predictions and some prior empirical findings, and may be partially explained by the scarcity of predators capable of penetrating the physical defenses of large seeds with hard seed coats. Large, soft seeds with low predation rates may have poor nutrition or may be protected by chemical defenses. Species differed greatly in 30-day germination rates, ranging from 0 to 47%. Some species with low predation rates also had low germination rates; the implications for the overall risk of predation during the seed stage are discussed. Predation rates were not associated with species' natural dispersal mode (clumped vs scatter-dispersed), contrary to theoretical predictions. Spiny rats (Maxomys spp.) were the most abundant seed eating rodent. Caged spiny rats avoided large, hard seeds and preferred soft, medium sized seeds. The substantial rates of post dispersal predation on isolated seeds that we measured may be sufficient to influence strongly the population dynamics and life history evolution of trees in this rain forest community.
Article
We measured the response of seed predators to variation in seed density and distance between seed sources of palms in North Queensland, Australia. Adult palm trees occurred at a density of 20/ha. Their distribution was highly clumped and more than half the immature plants occurred within 3 m of an adult. Adult palms were also arranged in lines down the slope, apparently reflecting patterns of seed carriage by overland water flow. Seed dispersal is also affected by cassowaries, a ratite which ranges over many hundreds of ha and deposits seeds in clusters. Small mammals which range over a few ha may deposit seeds as single entities (singletons). Many seeds remain undispersed beneath the female parent with heavy predation. In this study seeds were placed beneath adult trees at two densities and were dispersed over varying distances as clusters of ten seeds and as singletons. Pigs and earwigs were the principal predators but they did not destroy all the seeds in any treatment. However, the germination percentage of the remaining seeds was greatly depressed indicating that one or both predators were disproportionately selecting potential germinants. Pigs were responsive to both density of seeds beneath a tree and the distance between seed sources; they did not damage dispersed seeds to a great extent. Earwigs also destroyed seeds more heavily beneath adult trees, but they were more efficient than pigs at locating dispersed seeds. Rodent predation was light and not responsive to seed density or dispersal.
Article
A survey is presented of the plant families and genera recorded in the diet of frugivorous birds in the four main tropical forest regions (tropical America, Africa, southeast Asia, Australasia), a distinction being drawn between fruits eaten by specialized frugivores and those eaten by unspecialized, opportunist frugivores. The characteristics of fruits eaten by the two classes of frugivores are discussed, and available data on their size, composition, and nutritive content are tabulated. Fruits eaten by specialized frugivores are generally large, and have relatively large seeds and high nutritive quality. Of the plant families which have coevolved with frugivorous birds to produce fruits of this kind, three (Lauraceae, Burseraceae, and Palmae) are of outstanding importance. By comparison with the American tropics and Australasia, the forest flora of Africa is poor in plants of these families, and the number of specialized frugivores is also small. The possibility that there was formerly a richer assemblage of specialized frugivores in Africa, now extinct, is briefly discussed.
Article
There are simple standard tests for the comparison of samples assumed to arise from exponential distributions, but the properties of these tests are known to depend severely on the assumption of exponential form. However, the observations can sometimes usefully be ranked, and then replaced by the corresponding expected values of order statistics in sampling the unit exponential distribution, before calculating the appropriate test statistic. Some special tests of this type are examined. The procedure is analogous to the use of Fisher and Yates's scores in normal theory. Savage (1956) gave the test of this type for comparing two samples, in the course of a general study of rank tests for the two‐sample problem.
Chapter
This book provides information on the historical and theoretical perspectives of biodiversity and ecology in tropical forests, plant and animal behaviour towards seed dispersal and plant-animal interactions within forest communities, consequences of seed dispersal, and conservation, biodiversity and management.
Article
Germination percentage was increased and emergence was accelerated when two or more subterranean clover (Trifolium subterraneum L.) seeds were planted in close physical proximity instead of singly. The effect was enhanced when a nutrient solution was supplied. However, raising the ambient temperature from 10 to 15C and from 15 to 20C either reduced the effects of seed aggregation and nutrient availability or caused the effects to be evidenced during a shorter time interval. As the influence of close seed spacing and improved nutrient availability were more pronounced at cool temperatures, they therefore could be of importance to stand establishment from new seedings in the California annual range when rainfall adequate to permit germination occurs later than normal. Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © . .
Article
The effect of poultry manure on yield and growth of corn was studied on an Elkton sandy loam, typic ochraquults clayey mixed mesic, in southern Delaware. Plots with six levels of manure 0, 22, 56, 90, 168, and 224 metric tons/ha and a fertilizer treatment 224 5 186 kg/ha (N P K) and 22 metric tons/ha manure plus 224 5 186 kg/ha (N P K) were laid out in a randomized block design with four replications in 1971. Germination and yield of corn (Zea mays L.) were reduced by higher rates of poultry manure. Leaf mineral nutrition, the nitrogen fraction, organic acids, total ethanol soluble sugars, leaf water potential, leaf area index, soil salinity, and soil test data were determined to find the factors that contributed most to the yield reduction. Excessive soil salinity was considered to be the most important cause of the yield reduction following the application of high rates of poultry manure.
Article
The timing and levels of flowering and fruiting were studied in a premontane rain forest in western Colombia. Flower production is less seasonal than fruit production, and periods of peak fruiting do not always closely follow the periods of higher flowering activity. Fruit production is more equitably distributed through the year than in seasonal tropical environments, but there are two small fruiting peaks that center on the wetter portions of the year. Proportionally fewer canopy species than understory species produce bird-dispersed fruits, and almost all understory trees produce this type of fruit. Species of Miconia fruit sequentially through the year, but the total number of individuals in fruit varies seasonally. This variation is apparently offset by an increase in fruiting activity of other trees as there is no marked seasonal depression in the availability of fruit for birds.
Article
The role of white-tailed rats (Uromys caudimaculatus) as dispersers of seeds of the Australian tropical rain forest tree Beilschmiedia bancroftii, (Lauraceae) was investigated by following the fates of seeds and seedlings over 2 y. Fruits of this tree are too large to be consumed by any avian frugivore except the southern cassowary (Casuarius casuarius), and the only other native mammal capable of dispersing the seeds is the musky rat kangaroo (Hypsiprimnodon moschatus). However, neither of these species has been documented to disperse the seeds of this tree. During a mast year, white-tailed rats cached seeds an average of 13 m from parent trees in a variety of microsites. Although none of the 61 cached seeds followed in this study survived to germination, comparison of seed, cache and seedling distributions suggested that most seedlings arose from rat-cached seeds. White-tailed rats cached seeds in both mast and non-mast years, but the time seeds remained on the forest floor and in caches was significantly shorter in non-mast years, suggesting that synchronous seed production increases the probability that some caches survive to germination. Because white-tailed rats are the most common and widespread native mammal capable of dispersing large-seeds, this study suggests that they may play an important role in the seed and seedling dynamics of large-seeded tree species in Australian tropical rain forests.
Article
Abstract While density dependence is a central issue in much of plant ecology, it is often overlooked during the crucial seed germination period of the plant life-cycle. Here, patterns of germination in relation to initial seed density for 12 phylogenetically-diverse perennial plant species are described from laboratory experiments. When each of the 12 species was analysed individually, seeds of Alysicarpus rugosus, Callistemon citrinus, Eragrostis curvula and Panicum miliaceum showed a significant decrease in the proportion of seeds germinating at high densities of conspecifics. A meta-analysis carried out by grouping 11 of the 12 species together revealed an overall significant effect for a decrease in the proportion of seeds germinating at high conspecific densities compared with low con-specific densities. Significant decreases in the proportion of seeds germinating are interpreted as risk reappraisal by seeds through dormancy in response to potentially hazardous conditions imposed by high density clusters of seeds all germinating at once. The four species that responded significantly to high densities individually were each treated at low densities with a leachate solution obtained from high density conspecifics. For Alysicarpus rugosus and Panicum miliaceum, this resulted in a significant decrease in the proportion of seeds germinating at simulated high densities implicating the leachate as a causative agent. Heterospecific effects were investigated similarly for A. rugosus and E. curvula by the addition of leachate from high density clusters of seeds of one species upon the other. Only A. rugosus decreased germination significantly through the addition of leachate. These results demonstrate the ability of seeds to predict environmental conditions of the habitat into which they will emerge in terms of potential competitive interactions from neighbouring seedlings.
Article
1. Many studies have examined the effects of frugivores on the germination of seeds of fleshy fruited plants. However, three key issues are rarely addressed: the need to measure germination of seeds in intact fruits; the effect of germination conditions on results; and the distinction between dead vs dormant seeds. 2. A literature review including 51 plant species from 28 families found that the often-measured scarification effect (germination of bird-defecated vs hand-cleaned seeds) is significantly smaller than the rarely-measured deinhibition effect (germination of hand-cleaned seeds vs those in intact fruits). 3. Both the literature review and new experimental data show that germination condi-tions affect germination. In particular, seeds in intact fruits have much lower germination percentages in Petri dishes than in the field. Poor germination from intact fruits in Petri dishes may be an artefact. 4. A field experiment with three New Zealand species showed variable effects of non-removal of the fruit pericarp. The retention of the pericarp had no effect on germina-tion in Nestegis cunninghamii ; increased the proportion of seeds entering dormancy in Melicytus lanceolatus ; and greatly increased seed mortality in Pennantia corymbosa . 5. Germination experiments must be designed carefully to evaluate accurately the risks for plants of frugivory mutualism failures.
Article
We investigated the diet of the southern cassowary (Casuarius casuarius) by identifying the seeds and fruits in fecal droppings encountered on a set of transects over 2 yr in upland rain forest in the wet tropics of North Queensland. A total of 198 droppings containing 56 plant species were found. We surveyed fleshy fruit availability over the subsequent 68 mo on transects in the same area to ascertain fruiting patterns in the study area. The number of droppings found each month did not correspond to the pattern of available fruit biomass. There was no relationship between the fruit traits of moisture content, flesh to seed mass ratio, color, or crop size to contribution of a species to the diet. During the lean fruiting season (May–July) cassowaries relied more on species that fruited continuously throughout the year as they were significantly over-represented in droppings, while annual fruiting species were under-represented. During months of high fruit availability (October–December), continuously fruiting species were still over-represented in the diet but became less important while annual and biennial species became more important. Significantly more species with large fruit and large seeds appeared in the diet than expected and we confirm that the cassowary contributes to the continued dispersal of these species over long distances and in large quantities.
Article
People have hunted mammals in tropical Asian forests for at least 40,000 yr. This period has seen one confirmed global extinction (the giant pangolin, Manis palaeojavanica) and range restrictions for several large mammals, but there is no strong evidence for unsustainable hunting pressure until the last 2000–3000 yr, when elephants, rhinoceroses, and several other species were progressively eliminated from the large parts of their ranges. Regional declines in most species have occurred largely within the last 50 yr. Recent subsistence hunting has typically focused on pigs and deer (hunted with dogs and spears or with snares), monkeys and other arboreal mammals (often caught with blowpipes), and porcupines and other rodents (smoked or dug out of burrows). Over the last 50 yr, the importance of hunting for subsistence has been increasingly outweighed by hunting for the market. The hunted biomass is dominated by the same species as before, sold mostly for local consumption, but numerous additional species are targeted for the colossal regional trade in wild animals and their parts for food, medicines, raw materials, and pets. Many populations of mammalian dispersers of large seeds and understory browsers have been depleted or eliminated, while seed predators have had a more variable fate. Most of this hunting is now illegal, but the law enforcement is generally weak. However, examples of successful enforcement show that hunting impacts can be greatly reduced where there is sufficient political will. Ending the trade in wild animals and their parts should have the highest regional conservation priority.
Article
Disperser effectiveness is the contribution a disperser makes to the future reproduction of a plant. Although it is a key notion in studies of seed dispersal by animals, we know little about what determines the effectiveness of a disperser. The role of the present paper is to review the available information and construct a hierarchical framework for viewing the components of disperser effectiveness.Effectiveness has both quantitative and qualitative components. The quantity of seed dispersal depends on (A) the number of visits made to the plant by a disperser and (B) the number of seeds dispersed per visit. The quality of seed dispersal depends on (A) the quality of treatment given a seed in the mouth and in the gut and (B) the quality of seed deposition as determined by the probability that a deposited seed will survive and become an adult. In this paper I review the ways disperser behavior, morphology and physiology can influence these major components of disperser effectiveness, and when data permit present preliminary analyses of relationships among components.
Article
Dispersal is a significant determinant of the pattern and process of invasions; however, weed dispersal distances are rarely described and descriptions of dispersal kernels are completely lacking for vertebrate-dispersed weeds. Here, we describe dispersal kernels generated by a native disperser, the endangered southern cassowary (Casuarius casuarius, L.) for an invasive, tropical rainforest plant, pond apple (Annona glabra, L.). Pond apple is primarily water-dispersed and is managed as such. We consider whether cassowary dispersal, as a numerically subordinate dispersal mode, provides an additional dispersal service that may modify the invasion process. In infested areas, pond apple seed was common in cassowary dung. Gut passage had no effect on the probability of single seed germination but deposition in clumps or as whole fruits reduced the probability of germination below that of single seeds. Gut passage times ranged from 65 to 1675 min. Combined with cassowary movement data, this resulted in estimated dispersal distances of 12.5-5212 m, with a median distance of 387 m (quartile range 112-787 m). Native frugivores can be effective dispersers of weeds in rainforest and even terrestrial dispersers can provide long-distance dispersal. Importantly, though pond apple might be expected to be almost entirely dispersed downstream and along the margins of aquatic and marine habitats, cassowaries provide dispersal upstream and between drainages, leading to novel dispersal outcomes. Even through the provision of small quantities of novel dispersal outcomes, subordinate dispersal modes can play a significant role in determining invasion pattern and influence the ultimate success of control programs by providing dispersal to locations unattainable via the primary mode.
Article
Growing interest in spatial ecology is promoting new approaches to the study of seed dispersal, one of the key processes determining the spatial structure of plant populations. Seed-dispersion patterns vary among plant species, populations and individuals, at different distances from parents, different microsites and different times. Recent field studies have made progress in elucidating the mechanisms behind these patterns and the implications of these patterns for recruitment success. Together with the development and refinement of mathematical models, this promises a deeper, more mechanistic understanding of dispersal processes and their consequences.
Article
A laboratory experiment was conducted to study the effect of different concentrations (0%, 5%, 10%, 15%, 20%, 25%, 50%, 75% and 100%) of distillery effluent (raw spent wash) on seed germination (%), speed of germination, peak value and germination value in some vegetable crops: tomato, chilli, bottle gourd, cucumber and onion. The distillery effluent did not show any inhibitory effect on seed germination at low concentration except in tomato, but in onion the germination was significantly higher (84%) at 10% concentration as against 63% in the control. Irrespective of the crop species, at highest concentrations (75% and 100%), complete failure of germination was observed. The speed of germination, peak value and germination value also followed a similar trend. We found that a concentration of 5% was critical for seed germination in tomato and bottle gourd, and 25% in the rest of the crops. Based on the tolerance to distillery effluent, the crops studied have been arranged in the following order: cucumber > chilli > onion > bottle gourd > tomato. We conclude that the effect of the distillery effluent is crop-specific and due care should be taken before using the distillery effluent for pre-sowing irrigation purposes.
Article
A distribution-free two-sample test is proporesearch-articlesed that is an extension of the Wilcoxon test to samples with arbitrary censoring on the right. The test is conditional on the pattern of observations. The null hypothesis is H0: F1(t) = F2(t) (t ≤ T) against either H1: F1(t) <F2 (t ≤ T) or H2: F1(t) < F2(t) or F1(t) > F2(t) (t ≤ T), where F1, F2 are cumulative distributions (discrete or continuous) of the observations and T is their upper limit. The test is shown to be asymptotically normal and consistent against one-sided alternatives F1(t) < F2(t) (t ≤ T) and against two-sided alternatives where either F1(t) < F2(t) or F2(t) > F2(t) (t≤T). The asymptotic efficiency of the test relative to the efficient parametric test when the distributions are exponential is at least 0.75 and increases with degree of censoring. When H0 is true, the test not seriously affected by real differences in the percentage censored in the two groups. Some comparisons are made for five cases of varying degrees of censoring and tying between probabilities from the exact test and those from the proposed test and these suggest the test is appropriate under certain conditions when the sample size is five in each group. A worked example is presented and some discussion is given to further problems.