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1.
An evaluation of alternative dispersal functions for trees 总被引：5，自引：5，他引：5
DAVID F. GREENE§ CHARLES D. CANHAM† K. DAVID COATES‡ PHILIP T. LEPAGE§ 《Journal of Ecology》2004,92(5):758-766
2.
Rhett D Harrison Sylvester Tan Joshua B. Plotkin Ferry Slik Matteo Detto Tania Brenes Akira Itoh Stuart J. Davies 《Ecology letters》2013,16(5):687-694
Hunting affects a considerably greater area of the tropical forest biome than deforestation and logging combined. Often even large remote protected areas are depleted of a substantial proportion of their vertebrate fauna. However, understanding of the long‐term ecological consequences of defaunation in tropical forests remains poor. Using tree census data from a large‐scale plot monitored over a 15‐year period since the approximate onset of intense hunting, we provide a comprehensive assessment of the immediate consequences of defaunation for a tropical tree community. Our data strongly suggest that over‐hunting has engendered pervasive changes in tree population spatial structure and dynamics, leading to a consistent decline in local tree diversity over time. However, we do not find any support for suggestions that over‐hunting reduces above‐ground biomass or biomass accumulation rate in this forest. To maintain critical ecosystem processes in tropical forests increased efforts are required to protect and restore wildlife populations. 相似文献
3.
Helene C. Muller-Landau 《Biotropica》2007,39(3):372-384
Hunting can change abundances of vertebrate seed predators and seed dispersers, causing species‐specific changes in seed dispersal and seed predation and altering seedling communities. What are the consequences of these changes for the adult plant community in the next generation and beyond? Here, I derive equations showing how reduced seed dispersal reduces plant reproduction by intensifying kin competition, increasing vulnerability to natural enemies, and reducing the proportion of seeds passing through disperser guts. I parameterize these equations with available empirical data to estimate the likely effects on next‐generation abundances. I then consider the indirect effects and longer‐term feedbacks of changed seed or adult abundances on reproductive rates due to density‐dependent interactions with natural enemies and mutualists, as well as niche differentiation with competitors, and discuss their likely qualitative effects. The factors limiting seed disperser and seed predator populations in natural and hunted forests emerge as critical for determining the long‐term effects of hunting on rates of seed dispersal and seed predation. For example, where seed dispersers are held to a constant abundance by hunters, decreases in the availability of their preferred food plants are expected to lead to increased per‐seed dispersal probabilities, potentially to the point of compensating for the initial disperser decline. I close by discussing the likely reversibility of hunting‐induced changes in tropical forests and key questions and directions for future research. 相似文献
4.
Edu O. Effiom Gabriela Nu?ez-Iturri Henrik G. Smith Ulf Ottosson Ola Olsson 《Proceedings. Biological sciences / The Royal Society》2013,280(1759)
To assess ecological consequences of bushmeat hunting in African lowland rainforests, we compared paired sites, with high and low hunting pressure, in three areas of southeastern Nigeria. In hunted sites, populations of important seed dispersers—both small and large primates (including the Cross River gorilla, Gorilla gorilla diehli)—were drastically reduced. Large rodents were more abundant in hunted sites, even though they are hunted. Hunted and protected sites had similar mature tree communities dominated by primate-dispersed species. In protected sites, seedling communities were similar in composition to the mature trees, but in hunted sites species with other dispersal modes dominated among seedlings. Seedlings emerging 1 year after clearing of all vegetation in experimental plots showed a similar pattern to the standing seedlings. This study thus verifies the transforming effects of bushmeat hunting on plant communities of tropical forests and is one of the first studies to do so for the African continent. 相似文献
5.
6.
Felipe P. L. Melo Bernal Rodriguez-Herrera Robin L. Chazdon Rodrigo A. Medellin Gerardo G. Ceballos 《Biotropica》2009,41(6):737-743
In Neotropical regions, fruit bats are among the most important components of the remaining fauna in disturbed landscapes. These relatively small-bodied bats are well-known dispersal agents for many small-seeded plant species, but are assumed to play a negligible role in the dispersal of large-seeded plants. We investigated the importance of the small tent-roosting bat Artibeus watsoni for dispersal of large seeds in the Sarapiquí Basin, Costa Rica. We registered at least 43 seed species > 8 mm beneath bat roosts, but a species accumulation curve suggests that this number would increase with further sampling. Samples collected beneath bat feeding roosts had, on average, 10 times more seeds and species than samples collected 5 m away from bat feeding roosts. This difference was generally smaller in small, disturbed forest patches. Species-specific abundance of seeds found beneath bat roosts was positively correlated with abundance of seedlings, suggesting that bat dispersal may influence seedling recruitment. Our study demonstrates a greater role of small frugivorous bats as dispersers of large seeds than previously thought, particularly in regions where populations of large-bodied seed dispersers have been reduced or extirpated by hunting. 相似文献
7.
Hunting and habitat loss represent an increasingly common anthropogenic impact. Available evidence suggests that defaunation is typically differential: medium/large mammals are most affected while small rodents are less affected, or even favored. In heavily impacted areas, such as Los Tuxtlas, the residual mammalian fauna is dominated by small rodents. We tested the expectation that if small rodents will preferentially attack small-seeded species, large-seeded species may escape predation in the absence of medium/large seed predators and that this may affect germination and, possibly, recruitment. Experiments with caged rodents ( Heteromys desmarestianus ) under laboratory conditions showed a preference for smaller seeds. A field experiment involving seeds of contrasting size showed that small, unprotected seeds experienced a predation risk 30-times larger than protected seeds, while the effect of protection was not significant for large seeds. These patterns of predation led to significant differences in germination: protected small-seeded species had a fourfold greater germination than unprotected small-seeded species, while germination was not significantly different between exposed and protected large seeds. The observed contrasts in germination suggest that under heavy defaunation, small-seeded species are likely to be penalized by the overabundance of small rodents, while large-seeded species escape predation. Our results are consistent with the observation of dense seedling carpets dominated by large-seeded species in the understory of Los Tuxtlas. We speculate that the patterns we uncovered may explain, at least partly, the impoverished diversity of the understory vegetation that characterizes heavily defaunated understories and that this has the potential to affect forest regeneration. 相似文献
8.
Following defaunation, the loss of interactions with mutualists such as pollinators or seed dispersers may be compensated through increased interactions with remaining mutualists, ameliorating the negative cascading impacts on biodiversity. Alternatively, remaining mutualists may respond to altered competition by reducing the breadth or intensity of their interactions, exacerbating negative impacts on biodiversity. Despite the importance of these responses for our understanding of the dynamics of mutualistic networks and their response to global change, the mechanism and magnitude of interaction compensation within real mutualistic networks remains largely unknown. We examined differences in mutualistic interactions between frugivores and fruiting plants in two island ecosystems possessing an intact or disrupted seed dispersal network. We determined how changes in the abundance and behavior of remaining seed dispersers either increased mutualistic interactions (contributing to “interaction compensation”) or decreased interactions (causing an “interaction deficit”) in the disrupted network. We found a “rich‐get‐richer” response in the disrupted network, where remaining frugivores favored the plant species with highest interaction frequency, a dynamic that worsened the interaction deficit among plant species with low interaction frequency. Only one of five plant species experienced compensation and the other four had significant interaction deficits, with interaction frequencies 56–95% lower in the disrupted network. These results do not provide support for the strong compensating mechanisms assumed in theoretical network models, suggesting that existing network models underestimate the prevalence of cascading mutualism disruption after defaunation. This work supports a mutualist biodiversity‐ecosystem functioning relationship, highlighting the importance of mutualist diversity for sustaining diverse and resilient ecosystems. 相似文献
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10.
Andrew P. Nield Neal J. Enright Philip G. Ladd George L. W. Perry 《Population Ecology》2019,61(3):333-348
Disruption of seed dispersal processes may affect plant population spatial structure. We used a spatial simulation model and an empirical case study to assess the conditions under which the loss of seed dispersers has a detectable effect on a species' spatial pattern. Our simulation experiments suggested that detecting spatial change following disperser loss will be difficult, except when rates of fruit removal are initially high and then completely disappear. To contextualize the simulation modeling, we used spatial point pattern analyses to characterize the spatial pattern of two large-seeded species (Leucopogon nutans, a fire-killed seeder shrub and Macrozamia riedlei, a long-lived, resprouting cycad) in the jarrah (Eucalyptus marginata) forests of southwestern Australia. The plant species' primary disperser, the emu (Dromaius novaehollandiae), was absent from one of the sites we considered, but present at the other two. There was no detectable difference for either plant species in the strength of aggregation between sites with and without emu. However, even if disperser loss may not greatly affect local spatial structure for most plant species, it is likely to be important for long distance dispersal and genetic structuring of populations, so accurate characterization of the dispersal kernel is critical, especially in terms of plant emigration. 相似文献
11.
In Neotropical forests, large fruit-eating primates play important ecological roles as dispersal agents of large seeds. Bushmeat hunting threatens to disrupt populations of primates and large-seeded trees. We test the hypothesis that otherwise intact Neotropical forests with depressed populations of large primates experience decline in recruitment of large-seeded trees. We quantify the proportion of small juveniles (> 0.5 m tall–1 cm diameter at breast height, DBH) of large primate-dispersed tree species found underneath heterospecifc trees that are also dispersed by large primates at two protected sites in Manu National Park and one hunted site outside Manu N.P. in southeastern Peru. The forests are comparable in edaphic and climatic qualities, successional stage, and adult tree species composition. We found that hunting locally exterminates populations of large primates, and reduced primates of intermediate body size (hereafter \"medium primates\") by 80 percent. Moreover, tree species richness was 55 percent lower and density of species dispersed by large and medium-bodied primates 60 percent lower in hunted than in protected sites. In addition, richness and density of abiotically dispersed species and plants dispersed by non-game animals are greater in hunted sites. Overhunting threatens to disrupt the ecological interactions between primates and the plants that rely on them for seed dispersal and recruitment. Sustainable wildlife management plans are urgently needed, because protected areas are at risk of becoming \"island\" parks if buffer zones become empty of animals and have impoverished flora. 相似文献
12.
Diaspore (e.g. seeds, fruits) dispersal is pivotal for plant communities and often involves several steps and different dispersing agents. Most studies focusing on diaspore dispersal by animals have highlighted the role of vertebrates, neglecting the role of ants in the diaspore dispersal of non-myrmecochorous plants. Diaspore dispersal by ants is especially relevant in the current scenario of declining of vertebrate populations and, consequently, collapse of the dispersal system of large-seeded plants. Although ants can never compensate for the dispersal service provided by vertebrates, they can mitigate the impact of vertebrate decline via removal of diaspores deposited on the ground. We have used a meta-analytical approach to investigate the contribution of ants in the removal of non-myrmecochorous diaspores (through vertebrate exclusion experiments). We considered the number of diaspore removal as effect size and factors such as plant growth forms, diaspore and ant size, habitat type as moderators. In addition, we investigated the role of such factors on the diaspore removal distance by ants. Ants played complementary role to non-myrmecochorous diaspore removal services provided by vertebrates (mean Hedges’ g of −0.30). The ant diaspore removal was 69% higher for diaspores from shrubs than that of tree diaspores and removal of small-sized diaspores were 69% and 70% higher in comparison to medium- and large-sized diaspores, respectively. Regarding the diaspore removal distance by ants, those of tree species were removed 32% farther than those of shrub species, and diaspores were removed three- times farther in the savanna than in rainforest ecosystems. Our results highlight the shrubs and small-sized diaspores. Regarding the diaspore removal distance, the ants can be crucial for the dispersal of tree diaspores and in the savanna ecosystems. Finally, considering the biodiversity crisis, the ants may play an even more important role than appreciated in diaspores dispersal. 相似文献
13.
Kathryn E. Stoner Pablo Riba-Hernández Kevina Vulinec Joanna E. Lambert 《Biotropica》2007,39(3):316-327
Mammal populations are increasingly hunted, yet the consequences of their disappearance from tropical forests have only recently been explored. Here, we summarize current research on the role of mammals in seed dispersal and postdispersal processes, such as seed predation and secondary dispersal, in different tropical regions. We evaluate how mammal features influence seedshadows and ultimately forest regeneration. Finally, we discuss the potential effect of changes in seedshadows caused by the elimination of many medium- and large-sized mammals. The complex role that mammals play in creating and modifying seedshadows in tropical forests cannot be easily quantified, and in this review we emphasize the variation that exists both within and among mammal taxa and across continents. To bridge this gap in information, we suggest that more studies should evaluate the relative importance of the disappearance of both seed dispersers and seed predators for particular plant species so that we may begin to understand the balance between these two influences. We also suggest that future studies identify ecological redundancy in nonhunted vertebrates within any particular community to evaluate compensatory behavior that may help ameliorate some of the negative effects of hunting of large and medium mammals. 相似文献
14.
Forest rehabilitation activities have been initiated on degraded peatland at several sites in Southeast Asia. In order to achieve rehabilitation efficiently and on the largest possible scale, cost‐effective, transferable methods need to be established. One potential method, which has previously proven successful in both temperate and neotropical forest ecosystems, is the construction of artificial bird perches outside the forest edge. These provide resting perches for frugivorous birds, encouraging them to fly out of the forest, thus increasing seed dispersal and subsequent seedling recruitment into the degraded area. This method was trialled for the first time in degraded tropical peat swamp forest in Indonesia. The results show that the perches were used by frugivorous birds, leading to a significant increase in seed dispersal; however, seedling recruitment was not increased. The frugivorous birds using the perches were degraded zone species and dispersed mainly tree species from the degraded area. Furthermore, while some seeds of forest‐area tree species were dispersed, largely only the degraded area tree species survived to seedling stage. Neither seasonality nor distance from forest edge proved to be significant factors influencing seed dispersal or seedling recruitment, the latter highlighting that seeds were principally being dispersed from within the degraded area rather than from the forest. Although artificial perches did increase seed dispersal, their use as an actual restoration tool in the process of forest regeneration on degraded tropical peatland is limited. Furthermore, when the cost‐ and effort‐to‐area factors are considered, this method is shown to be inefficient. 相似文献
15.
We characterized the dispersal spectra and phenology of 298 vascular plant species of the sandstone plateaus of Colombian Amazonia. Dispersal modes were determined by the morphology of dispersion units, personal observations on fruit consumption, and an extensive literature review. We obtained the number of species per dispersal mode for the sandstone plateaus and for two recognized vegetation types: open‐herbaceous vegetation and low forest‐shrub vegetation. Dispersal modes were assigned to 295 plant species. Animals dispersed the highest percentage of species (46.6%), while the percentage of autochorous and anemochorous species was 29.4 and 23 percent, respectively. The dispersal spectrum of the low forest‐shrub vegetation type, based on the coverage of every species, showed that percentages of anemochorous (40.2%) and zoochorous species (37.8%) were similar. Autochory was the most important seed dispersal mode of the open‐herbaceous vegetation (60%). Birds were the principal group of potential dispersers (58.9%) of zoochorous species and reptiles the least important. We found two marked fruiting peaks, one from the end of the dry season to the beginning of the wet season and the second one from the beginning to the middle of the dry season. Our results showed that besides the differences in the vegetation structure and floristic composition between the sandstone plateaus and the adjacent tall forest, there also exist differences in the dispersal spectra and the fruiting rhythms. 相似文献
16.
Many of the mammals undergoing drastic declines in tropical forests worldwide are important seed dispersers and seed predators, and thus changes in mammal communities due to hunting will affect plant recruitment. It has been hypothesized that larger-seeded species will suffer greater reductions in seed removal and thus greater increases in predispersal seed predation than smaller-seeded species. We compared primary and secondary seed removal and predispersal seed predation of two tree species between hunted and nonhunted sites in Central Panama. Seeds of Oenocarpus mapora (Arecaceae) are 16-times greater in size than those of Cordia bicolor (Boraginaceae). We quantified primary seed removal and predispersal seed predation using seed traps, and we assessed secondary seed removal using seed removal plots. Primary removal of C. bicolor was 43 percent lower in the hunted sites, while primary removal of O. mapora was not significantly different. Secondary removal of unprotected O. mapora seeds on the ground was 59 percent lower in hunted sites, while secondary removal of C. bicolor was not significantly different. Predispersal seed predation of O. mapora by mammals was significantly lower in hunted sites, while predispersal seed predation by insects was not significantly different in either species. In combination with other studies, our results suggest that seed size is not a reliable predictor of the impacts of hunting. Mammal defaunation differentially affects stages and modes of seed dispersal and seed predation of different plant species, suggesting that these influences are complex and related to multiple plant traits. 相似文献
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18.
森林种子雨研究进展与展望 总被引：5，自引：0，他引：5
种子雨阶段是植物更新的关键环节,它连接着繁殖生产与植物后续生活史阶段,对群落结构有着重要的影响.虽然早在19世纪中叶达尔文就认识到种子扩散的重要性,然而对种子雨的广泛研究于20世纪80年代初才开始.本文聚焦于森林木本植物种子雨研究,首先介绍了种子雨监测方法,包括收集器的布置,种子雨的收集、分离和鉴定.然后综述了种子雨的4个主要研究方向:种子产量的时间和空间变化格局(包括季节变化、年际变化和空间变化)、增补限制及其在物种多样性维持中的作用、验证负密度效应假说、种子雨与其他生活史阶段(土壤种子库、幼苗、幼树及母树)的比较.未来还需要加强对种子雨的长期监测,开展增补限制的跨纬度比较研究,探讨植物早期更新阶段负密度效应沿纬度梯度的变化规律,加强数学模型以及分子标记和稳定同位素技术等新手段的运用. 相似文献
19.
Mauro Galetti Roger Guevara Lígia A. Galbiati Carolina L. Neves Raisa R. Rodarte Calebe P. Mendes 《Biotropica》2015,47(5):521-525
Rodents are known to perform post‐dispersal seed predation in tropical rain forest, but there is little information on the identity of these seed predators and how they select their seeds. Using cafeteria experiments, we found that seed mass, rodent body mass, and the ratio of seed/rodent mass were determinants of seed consumption. 相似文献
20.
Javier Valverde Carolina da Silva Carvalho Pedro Jordano Mauro Galetti 《Biotropica》2021,53(1):286-295
Large mammalian herbivores play an important role in shaping the diversity of tropical forests by affecting the survival of seedlings and saplings beneath parent plants. The white‐lipped peccary (Tayassu pecari) accounts for the largest herbivore biomass that controls seed and seedling survival in Neotropical ecosystems. However, hunting and habitat loss has driven peccaries to local extinction for most of their original distribution, so it is likely that their absence will affect plant recruitment dynamics. We tested the effects of peccary local extinction on the density and spatial distribution of the hyperdominant palm Euterpe edulis by performing a fine‐scale characterization of its spatial recruitment in six forest sites in the Brazilian Atlantic forest. We compared the age structure and the spatial patterns of seedlings, saplings, and adults as well as the relationship between them. We found that while under the presence of peccaries there was a decrease in recruitment rates under adults, the local extinction of these large mammals led to a more clumped process of spatial recruitment. Despite such contrasting spatial patterns of recruitment dynamics, neither age structure nor the random spatial distribution of adults was affected by the presence or absence of peccaries, indicating that their early effects on these palm populations are mitigated as recruitment advances. Our findings highlight the role of large‐bodied forest‐dwelling herbivores in regulating the fine‐scale spatial recruitment of plants and advance our understanding on the effects of defaunation in tropical forests. Abstract in Portuguese is available with online material. 相似文献