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1.
The estimation of phylogenetic relationships and divergence times among a group of organisms is a fundamental first step toward understanding its biological diversification. The time of the most recent or last common ancestor (LCA) of extant platyrrhines is one of the most controversial among scholars of primate evolution. Here we use two molecular based approaches to date the initial divergence of the platyrrhine clade, Bayesian estimations under a relaxed-clock model and substitution rate plus generation time and body size, employing the fossil record and genome datasets. We also explore the robustness of our estimations with respect to changes in topology, fossil constraints and substitution rate, and discuss the implications of our findings for understanding the platyrrhine radiation. Our results suggest that fossil constraints, topology and substitution rate have an important influence on our divergence time estimates. Bayesian estimates using conservative but realistic fossil constraints suggest that the LCA of extant platyrrhines existed at ca. 29 Ma, with the 95% confidence limit for the node ranging from 27–31 Ma. The LCA of extant platyrrhine monkeys based on substitution rate corrected by generation time and body size was established between 21–29 Ma. The estimates based on the two approaches used in this study recalibrate the ages of the major platyrrhine clades and corroborate the hypothesis that they constitute very old lineages. These results can help reconcile several controversial points concerning the affinities of key early Miocene fossils that have arisen among paleontologists and molecular systematists. However, they cannot resolve the controversy of whether these fossil species truly belong to the extant lineages or to a stem platyrrhine clade. That question can only be resolved by morphology. Finally, we show that the use of different approaches and well supported fossil information gives a more robust divergence time estimate of a clade.  相似文献   

2.
One of the central topics in evolutionary biology is understanding the processes responsible for phenotypic diversification related to ecological factors. New World monkeys are an excellent reference system to investigate processes of diversification at macroevolutionary scales. Here, we investigate the cranial shape diversification related to body size and ecology during the phylogenetic branching process of platyrrhines. To investigate this diversification, we used geometric morphometric techniques, a molecular phylogenetic tree, ecological data and phylogenetic comparative methods. Our statistical analyses demonstrated that the phylogenetic branching process is the most important dimension to understand cranial shape variation among extant platyrrhines and suggested that the main shape divergence among the four principal platyrrhine clades probably occurred during the initial branching process. The phylogenetic conservatism, which is the retention of ancestral traits over time within the four principal platyrrhine clades, could be the most important characteristic of platyrrhine cranial shape diversification. Different factors might have driven early shape divergence and posterior relative conservatism, including genetic drift, stabilizing selection, genetic constraints owing to pleiotropy, developmental or functional constraint, lack of genetic variation, among others. Understanding the processes driving the diversification among platyrrhines will probably require further palaeontological, phylogenetic and comparative studies.  相似文献   

3.
Several theories predict that rapidly diversifying clades will also rapidly diverge phenotypically; yet, there are also reasons for suspecting that diversification and divergence might not be correlated. In the widely distributed squirrel clade (Sciuridae), we test for correlations between per lineage speciation rates, species richness, disparity, and a time‐invariant measure of disparity that allows for comparing rates when evolutionary modes differ, as they do in squirrels. We find that species richness and speciation rates are not correlated with clade age or with each other. Disparity appears to be positively correlated with clade age because young, rapidly diversifying Nearctic grassland clades are strongly pulled to a single stable optimum but older, slowly diversifying Paleotropical forest clades contain lineages that diverge along multiple ecological and morphological lines. That contrast is likely due to both the environments they inhabit and their phylogenetic community structure. Our results argue against a shared explanation for diversity and disparity in favor of geographically mediated modes of speciation and ecologically mediated modes of phenotypic evolution.  相似文献   

4.
Puffins, auks and their allies in the wing‐propelled diving seabird clade Pan‐Alcidae (Charadriiformes) have been proposed to be key pelagic indicators of faunal shifts in Northern Hemisphere oceans. However, most previous phylogenetic analyses of the clade have focused only on the 23 extant alcid species. Here we undertake a combined phylogenetic analysis of all previously published molecular sequence data (~ 12 kb) and morphological data (n = 353 characters) with dense species level sampling that also includes 28 extinct taxa. We present a new estimate of the patterns of diversification in the clade based on divergence time estimates that include a previously vetted set of twelve fossil calibrations. The resultant time trees are also used in the evaluation of previously hypothesized paleoclimatic drivers of pan‐alcid evolution. Our divergence dating results estimate the split of Alcidae from its sister taxon Stercorariidae during the late Eocene (~ 35 Ma), an evolutionary hypothesis for clade origination that agrees with the fossil record and that does not require the inference of extensive ghost lineages. The extant dovekie Alle alle is identified as the sole extant member of a clade including four extinct Miocene species. Furthermore, whereas an Uria + Alle clade has been previously recovered from molecular analyses, the extinct diversity of closely related Miocepphus species yields morphological support for this clade. Our results suggest that extant alcid diversity is a function of Miocene diversification and differential extinction at the Pliocene–Pleistocene boundary. The relative timing of the Middle Miocene climatic optimum and the Pliocene–Pleistocene climatic transition and major diversification and extinction events in Pan‐Alcidae, respectively, are consistent with a potential link between major paleoclimatic events and pan‐alcid cladogenesis.  相似文献   

5.
The fossil record provides a lower bound on the primate divergence time of 54.8 million years ago, but does not provide an explicit estimate for the divergence time itself. We show how the pattern of diversification through the Cenozoic can be combined with a model for speciation to give a distribution for the age of the primates. The primate fossil record, the number of extant primate species, and information about the structure of the primate phylogenetic tree are combined to provide an estimate for the joint distribution of the primate and anthropoid divergence times. To take this information into account, we derive the structure of the birth-and-death process conditioned to have a subtree originate at a particular point in time. This process has a size-biased law and has an immortal line running from the root of the tree to the root of the subtree, with species on the spine having modified offspring and length distributions. We conclude that it is not possible, with this model, to rule out a Cretaceous origin for the primates.  相似文献   

6.
Snake diversity varies by at least two orders of magnitude among extant lineages, with numerous groups containing only one or two species, and several young clades exhibiting exceptional richness (>700 taxa). With a phylogeny containing all known families and subfamilies, we find that these patterns cannot be explained by background rates of speciation and extinction. The majority of diversity appears to derive from a radiation within the superfamily Colubroidea, potentially stemming from the colonization of new areas and the evolution of advanced venom-delivery systems. In contrast, negative relationships between clade age, clade size, and diversification rate suggest the potential for possible bias in estimated diversification rates, interpreted by some recent authors as support for ecologically mediated limits on diversity. However, evidence from the fossil record indicates that numerous lineages were far more diverse in the past, and that extinction has had an important impact on extant diversity patterns. Thus, failure to adequately account for extinction appears to prevent both rate- and diversity-limited models from fully characterizing richness dynamics in snakes. We suggest that clade-level extinction may provide a key mechanism for explaining negative or hump-shaped relationships between clade age and diversity, and the prevalence of ancient, species-poor lineages in numerous groups.  相似文献   

7.
A major goal of research in ecology and evolution is to explain why species richness varies across habitats, regions, and clades. Recent reviews have argued that species richness patterns among regions and clades may be explained by "ecological limits" on diversity over time, which are said to offer an alternative explanation to those invoking speciation and extinction (diversification) and time. Further, it has been proposed that this hypothesis is best supported by failure to find a positive relationship between time (e.g., clade age) and species richness. Here, I critically review the evidence for these claims, and propose how we might better study the ecological and evolutionary origins of species richness patterns. In fact, ecological limits can only influence species richness in clades by influencing speciation and extinction, and so this new "alternative paradigm" is simply one facet of the traditional idea that ecology influences diversification. The only direct evidence for strict ecological limits on richness (i.e., constant diversity over time) is from the fossil record, but many studies cited as supporting this pattern do not, and there is evidence for increasing richness over time. Negative evidence for a relationship between clade age and richness among extant clades is not positive evidence for constant diversity over time, and many recent analyses finding no age-diversity relationship were biased to reach this conclusion. More comprehensive analyses strongly support a positive age-richness relationship. There is abundant evidence that both time and ecological influences on diversification rates are important drivers of both large-scale and small-scale species richness patterns. The major challenge for future studies is to understand the ecological and evolutionary mechanisms underpinning the relationships between time, dispersal, diversification, and species richness patterns.  相似文献   

8.
Scaridae (parrotfishes) is a prominent clade of 96 species that shape coral reef communities worldwide through their actions as grazing herbivores. Phylogenetically nested within Labridae, the profound ecological impact and high species richness of parrotfishes suggest that their diversification and ecological success may be linked. Here, we ask whether parrotfish evolution is characterized by a significant burst of lineage diversification and whether parrotfish diversity is shaped more strongly by sexual selection or modifications of the feeding mechanism. We first examined scarid diversification within the greater context of labrid diversity. We used a supermatrix approach for 252 species to propose the most extensive phylogenetic hypothesis of Labridae to date, and time-calibrated the phylogeny with fossil and biogeographical data. Using divergence date estimates, we find that several parrotfish clades exhibit the highest diversification rates among all labrid lineages. Furthermore, we pinpoint a rate shift at the shared ancestor of Scarus and Chlorurus, a scarid subclade characterized by territorial behaviour and strong sexual dichromatism, suggesting that sexual selection was a major factor in parrotfish diversification. Modifications of the pharyngeal and oral jaws that happened earlier in parrotfish evolution may have contributed to this diversity by establishing parrotfishes as uniquely capable reef herbivores.  相似文献   

9.
Primates represent one of the most species rich, wide ranging, and ecologically diverse clades of mammals. What major macroevolutionary factors have driven their diversification and contributed to the modern distribution of primate species remains widely debated. We employed phylogenetic comparative methods to examine the role of clade age and evolutionary rate heterogeneity in the modern distribution of species diversity of Primates. Primate diversification has accelerated since its origin, with decreased extinction leading to a shift to even higher evolutionary rates in the most species rich family (Cercopithecidae). Older primate clades tended to be more diverse, however a shift in evolutionary rate was necessary to adequately explain the imbalance in species diversity. Species richness was also poorly explained by geographic distribution, especially once clade age and evolutionary rate shifts were accounted for, and may relate instead to other ecological factors. The global distribution of primate species diversity appears to have been strongly impacted by heterogeneity in evolutionary rates.  相似文献   

10.
Contemporary insights from evolutionary ecology suggest that population divergence in ecologically important traits within predators can generate diversifying ecological selection on local community structure. Many studies acknowledging these effects of intraspecific variation assume that local populations are situated in communities that are unconnected to similar communities within a shared region. Recent work from metacommunity ecology suggests that species dispersal among communities can also influence species diversity and composition but can depend upon the relative importance of the local environment. Here, we study the relative effects of intraspecific phenotypic variation in a fish predator and spatial processes related to plankton species dispersal on multitrophic lake plankton metacommunity structure. Intraspecific diversification in foraging traits and residence time of the planktivorous fish alewife (Alosa pseudoharengus) among coastal lakes yields lake metacommunities supporting three lake types which differ in the phenotype and incidence of alewife: lakes with anadromous, landlocked, or no alewives. In coastal lakes, plankton community composition was attributed to dispersal versus local environmental predictors, including intraspecific variation in alewives. Local and beta diversity of zooplankton and phytoplankton was additionally measured in response to intraspecific variation in alewives. Zooplankton communities were structured by species sorting, with a strong influence of intraspecific variation in A. pseudoharengus. Intraspecific variation altered zooplankton species richness and beta diversity, where lake communities with landlocked alewives exhibited intermediate richness between lakes with anadromous alewives and without alewives, and greater community similarity. Phytoplankton diversity, in contrast, was highest in lakes with landlocked alewives. The results indicate that plankton dispersal in the region supplied a migrant pool that was strongly structured by intraspecific variation in alewives. This is one of the first studies to demonstrate that intraspecific phenotypic variation in a predator can maintain contrasting patterns of multitrophic diversity in metacommunities.  相似文献   

11.
Birds play an important role in studies addressing the diversity and species richness of tropical ecosystems, but because of the poor avian fossil record in all extant tropical regions, a temporal perspective is mainly provided by divergence dates derived from calibrated molecular analyses. Tropical ecosystems were, however, widespread in the Northern Hemisphere during the early Cenozoic, and the early Eocene German fossil site Messel in particular has yielded a rich avian fossil record. The Messel avifauna is characterized by a considerable number of flightless birds, as well as a high diversity of aerial insectivores and the absence of large arboreal birds. With about 70 currently known species in 42 named genus‐level and at least 39 family‐level taxa, it approaches extant tropical biotas in terms of species richness and taxonomic diversity. With regard to its taxonomic composition and presumed ecological characteristics, the Messel avifauna is more similar to the Neotropics, Madagascar, and New Guinea than to tropical forests in continental Africa and Asia. Because the former regions were geographically isolated during most of the Cenozoic, their characteristics may be due to the absence of biotic factors, especially those related to the diversification of placental mammals, which impacted tropical avifaunas in Africa and Asia. The crown groups of most avian taxa that already existed in early Eocene forests are species‐poor. This does not support the hypothesis that the antiquity of tropical ecosystems is key to the diversity of tropical avifaunas, and suggests that high diversification rates may be of greater significance.  相似文献   

12.
Although there have been many studies of the ecology of primates in communities throughout the world, there have been few attempts to compare community ecology within and among continents. In this study the ecological characteristics of the sympatric primate species at eight localities—two from each of the major biogeographic areas inhabited by primates today—South America, Africa, Madagascar, and Asia—were compared using a multivariate technique (principal components analysis of the correlation matrix) to summarize the ten dimensional ecological niche space. The most striking clustering of species in ecological multivariate space is according to phylogeny with closely related species showing similar ecological features. Likewise, the ecological characteristics of individual communities are determined by phylogenetic groups present at each locality or biogeographic region. As a result, communities within any biogeographical region are more similar ecologically to one another than to communities from other continental areas. In several measures of ecological diversity among the species comprising each community, the neotropical communities show lower overall diversity than do communities from other continents.  相似文献   

13.
Patterns of geographic distribution and composition of fungal communities are still poorly understood. Widespread occurrence in terrestrial ecosystems and the unique richness of interactions of Sebacinales with plants make them a target group to study evolutionary events in the light of nutritional lifestyle. We inferred diversity patterns, phylogenetic structures and divergence times of Sebacinales with respect to their nutritional lifestyles by integrating data from fossil-calibrated phylogenetic analyses. Relaxed molecular clock analyses indicated that Sebacinales originated late Permian within Basidiomycota, and their split into Sebacinaceae and Serendipitaceae nom. prov. likely occurred during the late Jurassic and the early Cretaceous, coinciding with major diversifications of land plants. In Sebacinaceae, diversification of species with ectomycorrhizal lifestyle presumably started during the Paleocene. Lineage radiations of the core group of ericoid and cavendishioid mycorrhizal Sebacinales started probably in the Eocene, coinciding with diversification events of their hosts. The diversification of Sebacinales with jungermannioid interactions started during the Oligocene, and occurred much later than the diversification of their hosts. Sebacinales communities associated either with ectomycorrhizal plants, achlorophyllous orchids, ericoid and cavendishioid Ericaceae or liverworts were phylogenetically clustered and globally distributed. Major Sebacinales lineage diversifications started after the continents had drifted apart. We also briefly discuss dispersal patterns of extant Sebacinales.  相似文献   

14.
Traditional contributions of the insect fossil record are listed. Fossil material indicates the earliest occurrence of a group, which in turn is useful for inferring clade divergence dates and net diversification rates. Fossil material provides complementary information on the dynamics of taxonomic diversity. Geographical occurrences outside the extant range of a taxon can be used to infer climatic macro‐fluctuations. In short, the fossil record of insects is essential for pointing out the major factors responsible for the mega‐diversity of the group, and of some of its internal lineages. Reliable taxonomic assignments and phylogenetic hypotheses underpin broader generalizations. In that respect, a problem is the inadequate integration of data from fossil and extant insect taxa in phylogenetic investigations. Stumbling blocks lie at various systematic levels. Unreliability of specimen‐based data, of species delimitation, and of homology assumptions, might have been responsible for a disdain by some entomologists for palaeoentomological literature. Idiosyncratic (and in cases flawed) methods aimed at investigating phylogenetic relationships used by a fraction of the palaeoentomological community might also have contributed to this situation. Concurrently, the traditional nomenclatural procedure might prevent effective communication between neo‐ and palaeoentomologists. Augmenting the available information on the wing venation of extant taxa would significantly advance palaeoentomology, and provide a relevant broad‐scale character system. Furthermore, the entomological community should contribute to experimentations of various nomenclatural procedures, with the aim of developing an optimal approach in terms of communication and information retrieval.  相似文献   

15.
Allopatric or sympatric speciation influence the degree to which closely related species coexist in different manners, altering the patterns of phylogenetic structure and turnover among and between communities. The objective of this study was to examine whether phylogenetic community structure and turnover in the Brazilian Atlantic Forest permit conclusions about the dominant process for the formation of extant angiosperm richness of tree species. Therefore, we analyzed phylogenetic community structure (MPD, MNTD) as well as taxonomic (Jaccard similarity) and phylogenetic turnover (betaMPD, betaMNTD) among and between 49 tree communities distributed among three different habitat types. Mean annual precipitation and mean annual temperature in each survey area were estimated. Phylogenetic community structure does not differ between habitat types, although MPD reduces with mean annual temperature. Jaccard similarity decreases and betaMNTD increases with spatial distance and environmental differences between study sites. Spatial distance explains the largest portions of variance in the data, indicating dispersal limitation and the spatial aggregation of recently formed taxa, as betaMNTD is related to more recent evolutionary events. betaMPD, that is related to deep evolutionary splits, shows no spatial or environmental pattern, indicating that older clades are equally distributed across the Brazilian Atlantic Forest. While similarity pattern indicates dispersal limitations, the spatial turnover of betaMNTD is consistent with a high degree of sympatric speciation generating extant diversity and endemism in the Brazilian Atlantic Forest. More comprehensive approaches are necessary to reduce spatial sampling bias, uncertainties regarding angiosperm diversification patterns and confirm sympatric speciation as the dominant generator for the formation of extant species diversity in the Brazilian Atlantic Forest.  相似文献   

16.
刘瑞雪  林小龙  陈龙清 《生态学报》2023,43(11):4700-4711
群落谱系结构将物种系统发育信息整合到群落中,给生物多样性研究提供了全新视角。为探讨水淹干扰下水库水滨带植物群落物种多样性维持机制,以丹江口水库水滨带为研究区域,以南水北调中线一期工程运行前的原有水滨带植被为研究对象,分析不同水淹干扰强度下群落谱系结构和物种多样性及其与环境因素的关系。结果表明:(1)随着水淹干扰强度增加,群落物种丰富度、物种多样性和谱系多样性显著降低。谱系结构指数虽无显著差异,但随着水淹干扰强度增加呈现由发散到聚集的变化趋势。表明水滨带植物群落物种多样性维持机制是生境过滤和生态位分化共同驱动的结果,并且随着水淹干扰强度增加呈现生境过滤作用增加、物种间竞争排斥作用减弱的生态过程影响规律。(2)坡度、土壤质地、速效氮和全氮含量对整个水滨带植物群落物种丰富度、物种多样性和谱系多样性影响显著。此外,土层厚度和速效磷对物种丰富度和土层厚度对谱系多样性也影响显著。而仅有速效氮含量对谱系结构指数影响显著;轻度水淹干扰下坡向、速效磷含量与多样性指数显著相关;中度水淹干扰下坡度、土层厚度、土壤质地、土壤总氮含量与多样性指数显著相关,土壤pH、全氮和全磷含量与谱系结构指数显著相关;重度水淹...  相似文献   

17.
We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change.  相似文献   

18.
Understanding the processes underlying morphological diversification is a central goal in ecology and evolutionary biology and requires the integration of information about phylogenetic divergence and ecological niche diversity. In the present study, we use geometric morphometrics and comparative methods to investigate morphological diversification in Neotropical spiny rats of the family Echimyidae. Morphological diversification is studied as shape variation in the skull, comprising a structure composed of four distinct units: vault, base, orognathofacial complex, and mandible. We demonstrate association among patterns of variation in shape in different cranial units, levels of phylogenetic divergence, and ecological niche diversification. At the lower level of phylogenetic divergence, there is significant and positive concordance between patterns of phylogenetic divergence and cranial shape variation in all cranial units. This concordance may be attributable to the phylogenetic and shape distances being calculated between species that occupy the same niche. At higher phylogenetic levels of divergence and with ecological niche diversity, there is significant concordance between shape variation in all four cranial units and the ecological niches. In particular, the orognathofacial complex revealed the most significant association between shape variation and ecological niche diversity. This association may be explained by the great functional importance of the orognathofacial complex.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 646–660.  相似文献   

19.
THE MACROEVOLUTIONARY CONSEQUENCES OF ECOLOGICAL DIFFERENCES AMONG SPECIES   总被引:2,自引:0,他引:2  
Abstract:  In this paper, I examine the dynamics of species richness in a model system in which multiple species compete in a metacommunity (multiple patches linked by dispersal). Patches lie along an environmental gradient, and new species are introduced into the system by speciation of existing species. This model is used to explore how the ecological similarity of species influences the patterns in community structure that result and to determine whether patterns in fossil and systematics data may be signatures for different types of community structure. Making species more similar overall along the entire gradient or making new species that have more similar optimal positions along the gradient to their progenitor both increase the time required to drive species extinction. As a result, making species more similar ecologically to one another increases overall species richness because of an increased frequency of transient species in the system. Having more transient species in systems shifted the longevity distributions of species in the fossil record towards having a greater frequency of shorter duration species, and the age distribution of extant species that would be estimated from molecular phylogenies also had a higher frequency of younger aged species. Comparisons of these results with species longevity distributions extracted from two data sets and with species ages derived from species-level molecular phylogenies strongly suggest that transient species are an important component of real biological communities.  相似文献   

20.
Aim Our goals are: (1) to examine the relative degree of phylogenetic overdispersion or clustering of species in communities relative to the entire species pool, (2) to test for across‐continent differences in community phylogenetic structure, and (3) to examine the relationship between species richness and community phylogenetic structure. Location Africa, Madagascar, Asia, and the Neotropics. Methods We collected species composition and phylogenetic data for over 100 primate communities. For each community, we calculated two measures of phylogenetic structure: (1) the net relatedness index (NRI), which provides a measure of the mean pairwise phylogenetic distance among all species in the community; and (2) the nearest taxon index (NTI), which measures the relative phylogenetic distance among the closest related species in a community. Both measures are relative to the phylogeny of the species in the entire species pool. The phylocom package uses a randomization procedure to test whether the NRI and NTI values are higher or lower than expected by chance alone. In addition, we used a Kruskal–Wallis test to examine differences in NRI and NTI across continents, and linear regressions to examine the relationship between species richness and NRI/NTI. Results We found that the majority of individual primate communities in Africa, Asia and the Neotropics consist of member species that are neither more nor less closely related than expected by chance alone. Yet 37% of Malagasy communities contain species that are more distantly related to each other compared with random species assemblages. Also, we found that the average degree of relatedness among species in communities differed significantly across continents, with African and Malagasy communities consisting of more distantly related taxa compared with communities in Asia and the Neotropics. Finally, we found a significant negative relationship between species richness and phylogenetic distance among species in African, Asian and Malagasy communities. The average relatedness among species in communities decreased as community size increased. Main conclusions The majority of individual primate communities exhibit a phylogenetic structure no different from random. Yet there are across‐continent differences in the phylogenetic structure of primate communities that probably result from the unique ecological and evolutionary characteristics exhibited by the endemic species found on each continent. In particular, the recent extinctions of numerous primates on Madagascar are likely responsible for the low levels of evolutionary relatedness among species in Malagasy communities.  相似文献   

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