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1.
Ecol Lett ; 23(1): 160-171, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31698546

RESUMO

Among the local processes that determine species diversity in ecological communities, fluctuation-dependent mechanisms that are mediated by temporal variability in the abundances of species populations have received significant attention. Higher temporal variability in the abundances of species populations can increase the strength of temporal niche partitioning but can also increase the risk of species extinctions, such that the net effect on species coexistence is not clear. We quantified this temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. A fitted mechanistic model showed that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal variability in the abundances of species populations has no clear negative or positive contribution to the latitudinal gradient in tree species richness.


Assuntos
Biodiversidade , Árvores , Biota , Características de Residência
2.
Am J Primatol ; 81(8): e23036, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31338860

RESUMO

According to the sexual selection hypothesis, infanticide during resident male replacement is an adaptive strategy that has evolved because the killing of unweaned offspring sired by previous males shortens the inter-birth intervals of the mothers whose infants are targeted and thereby increases the reproductive fitness of the perpetrator. To test this hypothesis, we describe previously unreported cases of primary male replacement for two gibbon species (Hylobates lar and Nomascus nasutus), and review all other reported cases of primary male replacement in gibbons. Overall, infants were present in nearly half of all cases (16/33, 48%) and of the 18 infants present during replacement, 50% (N = 9) disappeared within 2 months of the event. In four of the five cases where there was sufficient demographic information to identify the likely sire of the subsequent offspring of females that lost infants, the new male was believed to be the sire. Infants were also less likely to die or disappear if the new male and original resident male were possible kin. However, there was no significant difference in the age of infants between those that died or disappeared following replacement and those that survived to weaning (p = .630). Our review of takeover-related infant loss in gibbons confirms that periods of male instability are risky for unweaned infants and that replacing males benefit from infant loss. Nevertheless, variability in the context of infant loss and difficulties related to data collection in the field make it difficult to test competing hypotheses concerning the mechanisms and functions of infanticide in the small apes.

3.
Sci Rep ; 9(1): 10015, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31292478

RESUMO

Recent studies have suggested that defaunation of large-bodied frugivores reduces above-ground carbon storage in tropical forests of South America and Africa, but not, or less so, in Southeast Asian tropical forests. Here we analyze the issue using the seed dispersal network (data of interaction between trees and animal seed dispersers) and forest composition of a 30-ha forest dynamics plot in central Thailand, where an intact fauna of primates, ungulates, bears and birds of all sizes still exists. We simulate the effect of two defaunation scenarios on forest biomass: 1) only primates extirpated (a realistic possibility in near future), and 2) extirpation of all large-bodied frugivores (LBF) including gibbons, macaques, hornbills and terrestrial mammals, the main targets of poachers in this region. For each scenario, we varied the population size reduction of the LBF dispersed tree species from 20% to 100%. We find that tree species dependent on seed dispersal by large-bodied frugivores (LBF) account for nearly one-third of the total carbon biomass on the plot, and that the community turnover following a complete defaunation would result in a carbon reduction of 2.4% to 3.0%, depending on the defaunation scenario and the model assumptions. The reduction was always greater than 1% when the defaunation intensity was at least 40%. These effect sizes are comparable to values reported for Neotropical forests, suggesting that the impact of defaunation on carbon deficit is not necessarily lower in Southeast Asian forests. The problem of defaunation in Asia, and the mutual benefits between biodiversity conservation and climate change mitigation, should therefore not be neglected by global policies to reduce carbon emissions.

4.
PLoS One ; 13(7): e0198960, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30020929

RESUMO

The world's largest terrestrial animals (megafauna) can play profound roles in seed dispersal. Yet, the term 'megafauna' is often used to encompass a diverse range of body sizes and physiologies of, primarily, herbivorous animals. To determine the extent to which these animals varied in their seed dispersal effectiveness (SDE), we compared the contribution of different megafauna for the large-fruited Platymitra macrocarpa (Annonaceae), in a tropical evergreen forest in Thailand. We quantified 'seed dispersal effectiveness' by measuring the quantity and quality contributions of all consumers of P. macrocarpa fruit. Seed dispersal quantity was the proportion of the crop consumed by each species. Quality was defined as the proportion of seeds handled by each animal taxon that survived to produce a 2-month seedling. Megafauna (elephants, sambar deer, bears) dispersed 78% of seeds that produced seedlings, with 21% dispersed by gibbons (a medium-sized frugivore). The main megafaunal consumers displayed different dispersal strategies. Elephants were the most effective dispersers (37% of seedlings) and they achieved this by being high-quality and low-quantity dispersers. Bears displayed a similar strategy but were especially rare visitors to the trees (24% of the total seedlings produced). Sambar were high-quantity dispersers, but most seeds they handled did not survive and they were responsible for only 17% of seedlings. Gibbons displayed a high SDE relative to their body size, but they probably cannot match the role of elephants despite being more regular consumers of the fruit. The low density and poor regeneration of P. macrocarpa in the study site suggest that current dispersal rates by megafauna are insufficient, possibly reflecting reduced or missing megafauna populations. We show that different megafaunal species disperse seeds in different ways and may make unique contributions to the reproductive success of the plant species.


Assuntos
Annonaceae/crescimento & desenvolvimento , Ecossistema , Dispersão de Sementes/fisiologia , Sementes/crescimento & desenvolvimento , Animais , Conservação dos Recursos Naturais , Cervos/fisiologia , Elefantes/fisiologia , Florestas , Frutas/genética , Frutas/crescimento & desenvolvimento , Herbivoria/fisiologia , Dispersão de Sementes/genética , Tailândia , Árvores , Ursidae/fisiologia
5.
Science ; 360(6391)2018 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-29798853

RESUMO

Hülsmann and Hartig suggest that ecological mechanisms other than specialized natural enemies or intraspecific competition contribute to our estimates of conspecific negative density dependence (CNDD). To address their concern, we show that our results are not the result of a methodological artifact and present a null-model analysis that demonstrates that our original findings-(i) stronger CNDD at tropical relative to temperate latitudes and (ii) a latitudinal shift in the relationship between CNDD and species abundance-persist even after controlling for other processes that might influence spatial relationships between adults and recruits.


Assuntos
Biodiversidade , Árvores , Densidade Demográfica , Plântula
6.
Science ; 360(6391)2018 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-29798855

RESUMO

Chisholm and Fung claim that our method of estimating conspecific negative density dependence (CNDD) in recruitment is systematically biased, and present an alternative method that shows no latitudinal pattern in CNDD. We demonstrate that their approach produces strongly biased estimates of CNDD, explaining why they do not detect a latitudinal pattern. We also address their methodological concerns using an alternative distance-weighted approach, which supports our original findings of a latitudinal gradient in CNDD and a latitudinal shift in the relationship between CNDD and species abundance.


Assuntos
Biodiversidade , Árvores , Ecossistema , Plântula
7.
R Soc Open Sci ; 5(9): 181168, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30839691

RESUMO

The relationship between ß-diversity and latitude still remains to be a core question in ecology because of the lack of consensus between studies. One hypothesis for the lack of consensus between studies is that spatial scale changes the relationship between latitude and ß-diversity. Here, we test this hypothesis using tree data from 15 large-scale forest plots (greater than or equal to 15 ha, diameter at breast height ≥ 1 cm) across a latitudinal gradient (3-30o) in the Asia-Pacific region. We found that the observed ß-diversity decreased with increasing latitude when sampling local tree communities at small spatial scale (grain size ≤0.1 ha), but the observed ß-diversity did not change with latitude when sampling at large spatial scales (greater than or equal to 0.25 ha). Differences in latitudinal ß-diversity gradients across spatial scales were caused by pooled species richness (γ-diversity), which influenced observed ß-diversity values at small spatial scales, but not at large spatial scales. Therefore, spatial scale changes the relationship between ß-diversity, γ-diversity and latitude, and improving sample representativeness avoids the γ-dependence of ß-diversity.

8.
Science ; 356(6345): 1389-1392, 2017 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-28663501

RESUMO

Theory predicts that higher biodiversity in the tropics is maintained by specialized interactions among plants and their natural enemies that result in conspecific negative density dependence (CNDD). By using more than 3000 species and nearly 2.4 million trees across 24 forest plots worldwide, we show that global patterns in tree species diversity reflect not only stronger CNDD at tropical versus temperate latitudes but also a latitudinal shift in the relationship between CNDD and species abundance. CNDD was stronger for rare species at tropical versus temperate latitudes, potentially causing the persistence of greater numbers of rare species in the tropics. Our study reveals fundamental differences in the nature of local-scale biotic interactions that contribute to the maintenance of species diversity across temperate and tropical communities.


Assuntos
Biodiversidade , Árvores/classificação , Antibiose , Ecossistema , Florestas , Geografia , Modelos Biológicos , Árvores/fisiologia , Clima Tropical
9.
Am J Phys Anthropol ; 163(4): 716-728, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28726303

RESUMO

OBJECTIVES: The study of related species in contact zones can elucidate what factors mediate species coexistence and geographical distributions. We investigated niche overlap and group interactions of two gibbon species and their hybrids co-occurring in a zone of overlap and hybridization. METHODS: The location, composition and behavior of white-handed, pileated, and mixed-species gibbon groups were studied by following them during 31 consecutive months in a relatively large part of the contact zone. RESULTS: Twenty groups of white-handed gibbon were mapped followed by nine groups of pileated gibbons and five mixed-species groups. White-handed, pileated and mixed-species groups had similar sizes and composition, ate a high proportion of fruits, shared a large number of species in their diets, and presented similar habitat preferences. Group home range sizes did not differ between species and overlapped little with neighboring groups irrespective of species, and intraspecific and interspecific encounter rates were similar. DISCUSSION: Ecological similarities support that competition between the gibbon species exists and takes the form of interspecific territoriality. However, we could not find any clear mechanism of niche partitioning favoring coexistence between species. Our findings suggest that the contact zone is unstable and is maintained by dispersal inward from groups of the parental species. The relatively low numbers of mixed-species groups and hybrids found suggests a high degree of premating reproductive isolation, perhaps mediated by interspecific miscommunication. The existence of hybrids and backcrosses potentially undetectable from phenotypic characters alone raises the possibility of more widespread introgression than has been evident. Hence, while interspecific territoriality should reduce the rate of gene transfer, it would not necessarily present a barrier to introgression into contiguous populations of the opposite species.


Assuntos
Ecossistema , Hylobates/fisiologia , Comportamento Social , Especificidade da Espécie , Animais , Antropologia Física , Evolução Biológica , Ecologia , Feminino , Comportamento de Retorno ao Território Vital , Masculino , Tailândia
10.
Am J Primatol ; 78(2): 192-203, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26456317

RESUMO

Ranging behavior is an important element of how nonhuman primates obtain sufficient resources to ensure biological maintenance and reproductive success. As most primates live in permanent social groups, group members must balance the benefits of group living with the costs of intragroup competition for resources. One way to mitigate the cost of intragroup feeding competition is to increase foraging-related travel, thereby increasing the number of patches visited. As a result we might expect home range size to increase as a function of group size. On the other hand, for perennially territorial species, ranging behavior may be constrained by the ranging requirements of territorial defense or by the location of neighboring territories, which would result in long-term stability in the size and location of a group's home range. In this study, we examined changes in range-use characteristics in one well-habituated group of white-handed gibbons (Hylobates lar) during three study periods over a 10-year span. Group size changed from five members, two adults, two juveniles, and one infant, in 1994, to two adults in 2002, and to three adults and one sub-adult in 2004. Despite inter-annual changes in core area use we found that home range location was highly stable across years. Nevertheless, home range size was larger and daily path length significantly longer in 2002 relative to 1994 when a dependent infant was present in the group. The percentage of time adults spent resting was also significantly greater in 1994 when the infant was present. These findings highlight the importance of considering group composition, in addition to group size, when evaluating the determinants of ranging behavior. We also consider the influence of individual and shared knowledge on home range stability.


Assuntos
Comportamento de Retorno ao Território Vital , Hylobates/fisiologia , Animais , Feminino , Masculino , Parques Recreativos , Reprodução , Estações do Ano , Tailândia
11.
Ecology ; 96(10): 2737-47, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26649394

RESUMO

The largest fruits found in tropical forests may depend on complementary seed dispersal strategies. These fruits are dispersed most effectively by megafauna, but populations can persist where megafauna are absent or erratic visitors. Smaller animals often consume these large fruits, but their capacity to disperse these seeds effectively has rarely been assessed. We evaluated the contributions of gibbons (Hylobates lar) and other frugivores in the seed dispersal of the megafaunal fruit Garcinia benthamii, using the SDE (seed dispersal effectiveness) landscape. Gibbons preferentially consumed G. benthamii fruits and were the main seed disperser that we observed. However, gibbons became satiated when availability was high, with 57% of fruits falling to the ground unhandled. Recruitment of seedlings from gibbon-dispersed seeds was also very low. Elephants consumed G. benthamii fruit, but occurred at low density and were rare visitors to the trees. We suggest that gibbons might complement the seed dispersal role of elephants for G. benthamii, allowing limited recruitment in areas (such as the study site) where elephants occur at low density. Fruit availability varied between years; when availability was low, gibbons reliably consumed most of the crop and dispersed some seeds that established seedlings, albeit at low numbers (2.5 seedlings per crop). When fruit availability was high, the fruit supply overwhelmed the gibbons and other arboreal frugivores, ensuring a large abundance of fruit available to terrestrial seed dispersers. Although gibbons effectively dispersed more seeds at these times (20.7 seedlings per crop), there was the potential for elephants to move many more seeds. Complementary seed dispersal strategies may be important for megafaunal fruit, because they ensure that very large fruits are able to benefit from megafaunal dispersal but also persist where this dispersal becomes erratic. However, our data suggest that smaller seed dispersers might not be capable of replacing large dispersers, leading to potential changes in landscape-scale dispersal patterns where megafauna are absent.


Assuntos
Garcinia/fisiologia , Hylobates/fisiologia , Sementes , Animais , Besouros , Demografia , Dieta , Florestas , Frutas , Macaca , Sciuridae , Fatores de Tempo
12.
Am J Primatol ; 77(5): 492-501, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25597291

RESUMO

We summarize the results from a long-term gibbon reintroduction project in Phuket, Thailand, and evaluate its benefits to conservation. Between October 2002 and November 2012, eight breeding families of white-handed gibbons (Hylobates lar) were returned to the wild in Khao Phra Thaew non-hunting area (KPT). Wild gibbons were extirpated from Phuket Island by the early 1980s, but the illegal wildlife trade has continued to bring young gibbons from elsewhere to the island's popular tourist areas as pets and photo props. The Gibbon Rehabilitation Project (GRP) has rescued and rehabilitated confiscated and donated captive gibbons since 1992 and aims to repopulate the island's last sizable forest area. Following unsuccessful early attempts at translocation in the 1990s, GRP has now developed specific methods for gibbon reintroduction that have led to the establishment of a small independent, reproducing population of captive-raised and wild-born gibbons on Phuket. Eleven infants have been born wild within the reintroduced population, including a second generation wild-born gibbon in September 2012. Benefits of the GRP project include restoration of the gibbon population on Phuket, rescue of illegally kept gibbons, public education, training of personnel in gibbon conservation work, and gaining experience which may prove useful in saving more severely threatened species. It is unlikely that gibbon (and other large primate) translocations will make a significant contribution to conservation of the species as a whole, and primate translocation projects should not be judged solely by this criterion.


Assuntos
Conservação dos Recursos Naturais , Hylobates , Reprodução , Animais , Feminino , Masculino , Dinâmica Populacional , Tailândia
13.
Glob Chang Biol ; 21(2): 528-49, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25258024

RESUMO

Global change is impacting forests worldwide, threatening biodiversity and ecosystem services including climate regulation. Understanding how forests respond is critical to forest conservation and climate protection. This review describes an international network of 59 long-term forest dynamics research sites (CTFS-ForestGEO) useful for characterizing forest responses to global change. Within very large plots (median size 25 ha), all stems ≥ 1 cm diameter are identified to species, mapped, and regularly recensused according to standardized protocols. CTFS-ForestGEO spans 25 °S-61 °N latitude, is generally representative of the range of bioclimatic, edaphic, and topographic conditions experienced by forests worldwide, and is the only forest monitoring network that applies a standardized protocol to each of the world's major forest biomes. Supplementary standardized measurements at subsets of the sites provide additional information on plants, animals, and ecosystem and environmental variables. CTFS-ForestGEO sites are experiencing multifaceted anthropogenic global change pressures including warming (average 0.61 °C), changes in precipitation (up to ± 30% change), atmospheric deposition of nitrogen and sulfur compounds (up to 3.8 g N m(-2) yr(-1) and 3.1 g S m(-2) yr(-1)), and forest fragmentation in the surrounding landscape (up to 88% reduced tree cover within 5 km). The broad suite of measurements made at CTFS-ForestGEO sites makes it possible to investigate the complex ways in which global change is impacting forest dynamics. Ongoing research across the CTFS-ForestGEO network is yielding insights into how and why the forests are changing, and continued monitoring will provide vital contributions to understanding worldwide forest diversity and dynamics in an era of global change.


Assuntos
Mudança Climática , Conservação dos Recursos Naturais , Monitoramento Ambiental , Florestas
14.
Primates ; 53(1): 97-108, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22127502

RESUMO

We investigated the ecology and interspecific interactions of the two gibbon species (Hylobates lar and H. pileatus) that overlap in distribution within a narrow zone of contact in the headwaters of the Takhong River at Khao Yai National Park in central Thailand. The zone is about 10-km wide, with phenotypic hybrids comprising 6.5% of the adult population. We compared species with respect to diet, territory size, intra- and interspecific group encounters, and territory quality. The two gibbon species exploited the same types of resources within their territories despite variation in the relative abundance of food-plant species between territories. The gibbons were interspecifically territorial, and males of both species displayed aggressive behaviors at both intraspecific and interspecific territorial boundaries. There was no marked difference in the amount of overlap between territories of conspecific and heterospecific pairs of groups. Although the habitat was not homogeneous, territory quality did not vary significantly between species. The species have not diverged in habitat preference or in diet. Neither species dominated in interspecific encounters, and both were reproducing well in the contact zone. We analyzed the potential consequences of several types of interspecific interactions on individual dispersal options and on the structure of the contact zone. Interference competition through interspecific territoriality affects the dispersal of individuals into the range of the other species. In general, territorial competition coupled with limited hybridization leads to predictions of a narrow contact zone or parapatry between species; thus, behavioral and ecological interactions between species need to be considered as potential factors in explaining range borders of primate species.


Assuntos
Dieta/veterinária , Hylobates/fisiologia , Territorialidade , Agressão , Animais , Evolução Biológica , Meio Ambiente , Feminino , Hibridização Genética , Hylobates/genética , Masculino , Dinâmica Populacional , Comportamento Social , Especificidade da Espécie , Tailândia
15.
Ecology ; 92(7): 1492-502, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21870623

RESUMO

Plant species with generalized dispersal mutualisms are considered to be robust to local frugivore extinctions because of redundancy between dispersal agents. However, real redundancy can only occur if frugivores have similar foraging and ranging patterns and if fruit is a limiting resource. We evaluated the quantitative and qualitative contributions of seed dispersers for an endochorus mast-fruiting species, Prunus javanica (Rosaceae) in Khao Yai National Park, Thailand, to evaluate the potential redundancy of dispersers. Data were collected from tree watches, seed/fruit traps, and seed transects under and away from fruiting trees, feeding and seed deposition by gibbons (Hylobates lar), and evaluations of seed and first-year seedling survival. We identified three clusters of dispersers within the network. Most (>80%) frugivore species observed were small birds and squirrels that were not functional dispersers, dropping most seeds under or very near the tree crown, where seedling survival was ultimately nil. Monkeys (Macaca leonina) were low-quality, short-range dispersers, but they dispersed large numbers of seeds and were responsible for 67% of surviving first-year seedlings. Gibbons and Oriental Pied Hornbills (Anthracoceros albirostris) handled few fruits, but they provided the highest quality service by carrying most seeds away from the canopy to medium and long distances, respectively. Although there was overlap in the deposition patterns of the functional dispersers, they displayed complementary, rather than redundant, roles in seed dispersal. Satiation of all functional dispersers further limited their capacity to "replace" one another. Redundancy must be evaluated at the community level because each type of disperser may shift to different species in the non-masting years of P. javanica. Our results underscore the need for research on broader spatial and temporal scales, which combines studies of dispersal and plant recruitment, to better understand mechanisms that maintain network stability.


Assuntos
Ecossistema , Árvores , Clima Tropical , Animais , Demografia
16.
Anim Cogn ; 14(3): 395-405, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21221693

RESUMO

Remembering locations of food resources is critical for animal survival. Gibbons are territorial primates which regularly travel through small and stable home ranges in search of preferred, limited and patchily distributed resources (primarily ripe fruit). They are predicted to profit from an ability to memorize the spatial characteristics of their home range and may increase their foraging efficiency by using a 'cognitive map' either with Euclidean or with topological properties. We collected ranging and feeding data from 11 gibbon groups (Hylobates lar) to test their navigation skills and to better understand gibbons' 'spatial intelligence'. We calculated the locations at which significant travel direction changes occurred using the change-point direction test and found that these locations primarily coincided with preferred fruit sources. Within the limits of biologically realistic visibility distances observed, gibbon travel paths were more efficient in detecting known preferred food sources than a heuristic travel model based on straight travel paths in random directions. Because consecutive travel change-points were far from the gibbons' sight, planned movement between preferred food sources was the most parsimonious explanation for the observed travel patterns. Gibbon travel appears to connect preferred food sources as expected under the assumption of a good mental representation of the most relevant sources in a large-scale space.


Assuntos
Metas , Hylobates/psicologia , Movimento , Animais , Meio Ambiente , Comportamento Alimentar , Feminino , Masculino , Comportamento Espacial
17.
Ecol Appl ; 19(4): 854-63, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19544729

RESUMO

Myriad tropical vertebrates are threatened by overharvest. Whether this harvest has indirect effects on nonhunted organisms that interact with the game species is a critical question. Many tropical birds and mammals disperse seeds. Their overhunting in forests can cause zoochorous trees to suffer from reduced seed dispersal. Yet how these reductions in seed dispersal influence tree abundance and population dynamics remains unclear. Reproductive parameters in long-lived organisms often have very low elasticities; indeed the demographic importance of seed dispersal is an open question. We asked how variation in hunting pressure across four national parks with seasonal forest in northern Thailand influenced the relative abundance of gibbons, muntjac deer, and sambar deer, the sole dispersers of seeds of the canopy tree Choerospondias axillaris. We quantified how variation in disperser numbers affected C. axillaris seed dispersal and seedling abundance across the four parks. We then used these data in a structured population model based on vital rates measured in Khao Yai National Park (where poaching pressure is minimal) to explore how variation in illegal hunting pressure might influence C. axillaris population growth and persistence. Densities of the mammals varied strongly across the parks, from relatively high in Khao Yai to essentially zero in Doi Suthep-Pui. Levels of C. axillaris seed dispersal and seedling abundance positively tracked mammal density. If hunting in Khao Yai were to increase to the levels seen in the other parks, C. axillaris population growth rate would decline, but only slightly. Extinction of C. axillaris is a real possibility, but may take many decades. Recent and ongoing extirpations of vertebrates in many tropical forests could be creating an extinction debt for zoochorous trees whose vulnerability is belied by their current abundance.


Assuntos
Anacardiaceae , Ecossistema , Hylobates , Cervo Muntjac , Sementes , Animais , Comportamento Alimentar , Hylobates/fisiologia , Modelos Biológicos , Cervo Muntjac/fisiologia , Densidade Demográfica , Crescimento Demográfico , Tailândia
18.
Ecology ; 90(3): 688-98, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19341139

RESUMO

Many plants interact with groups of mutualist pollinators and seed dispersers. A key issue for both basic ecology and conservation is whether the different species within these guilds of mutualist animals are functionally equivalent. Comparing the relative effects of sympatric mutualists is important for understanding the evolution of multispecies mutualisms and for predicting mutualism stability in the face of anthropogenic change. However, empirical comparisons of the population-level impacts of mutualist animals on their host plant are rare, particularly for seed dispersal mutualisms in species-rich ecosystems. We compared the influence of three seed-dispersing tropical mammals, lar gibbons (Hylobates lar), sambar deer (Rusa unicolor), and red muntjac deer (Muntiacus muntjak), on the demography of a shared host tree in Thailand, Choerospondias axillaris (Anacardiaceae). Sambar and muntjac dispersed far more C. axillaris seeds than did gibbons. While sambar deposited many seeds under female tree canopies, muntjac were the only disperser to move seeds to open microhabitats, where C. axillaris seed germination, seedling survival, and initial growth are enhanced. Using stage-based population models, we assessed how disperser-specific seed dispersal, variation in the frequency of canopy gap formation, and their interaction influenced the potential population growth of C. axillaris. Large differences in dispersal quantity and small differences in dispersal quality among sambar and gibbons resulted in similar and negligible impacts on the tree's population dynamics. Muntjac, by taking some of the seeds to open microhabitats, are projected to have a greater positive impact on C. axillaris demography than either sambar or gibbons. Model comparisons of population-level species impacts may allow us to predict which ecological interactions are at risk from loss of critical species.


Assuntos
Anacardiaceae/crescimento & desenvolvimento , Cervos/fisiologia , Ecossistema , Comportamento Alimentar/fisiologia , Hylobates/fisiologia , Anacardiaceae/fisiologia , Animais , Conservação dos Recursos Naturais , Demografia , Feminino , Masculino , Dinâmica Populacional
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