Scaling of species diversity and body mass in mammals: Cope’s rule and the evolutionary cost of large size

Abstract

Equations are constructed describing the inverse correlation of species diversity and body mass in extant and Cenozoic mammals. Cope’s rule, the tendency for many mammal clades to increase in body size through time, through phyletic change in single lineages or turnover within species groups, is interpreted as a probability function reducing diversity potential as a tradeoff for ecological/evolutionary gains. The inverse rule predicts that large species in clades will be less diverse than smaller species and, unless origination rates remain high among smaller clade members, clades conforming to Cope’s rule will decline in diversity, moving towards extinction. This proposition is evaluated in the Cenozoic histories of five North American mammal clades; cotton rats, felids, canids, hyaenodontids, and equids. Diversity potential of different size classes within the 3.75 million year phyletic history of the muskrat, Ondatra zibethicus, is also examined. A corollary prediction of the inverse rule, that large species should have longer durations (species lifespans) than small species, is unresolved. Successful clades maintain small size or a significant number of smaller species relative to clade average size. The potential loss of unique extant large mammal species justifies the conservation effort to protect them. The similarity of scaling exponents of species diversity to mass around a slope of -1.0 suggests that species diversity is correlated with home range size, the latter related to the probability of population fragmentation.     

Genome Size and Species Diversification

Theoretically, there are reasons to believe that large genome size should favour speciation. Several major factors contributing to genome size, such as duplications and transposable element activity have been proposed to facilitate the formation of new species. However, it is also possible that small genome size promotes speciation. For example, selection for genome reduction may be resolved in different ways in incipient species, leading to incompatibilities. Mutations and chromosomal rearrangements may also be more stably inherited in smaller genomes. Here I review the following lines of empirical evidence bearing on this question: (i) Correlations between genome size and species richness of taxa are often negative. (ii) Fossil evidence in lungfish shows that the accumulation of DNA in the genomes of this group coincided with a reduction in species diversity. (iii) Estimates of speciation interval in mammals correlate positively with genome size. (iv) Genome reductions are inferred at the base of particular species radiations and genome expansions at the base of others. (v) Insect clades that have been increasing in diversity up to the present have smaller genomes than clades that have remained stable or have decreased in diversity. The general pattern emerging from these observations is that higher diversification rates are generally found in small-genome taxa. Since diversification rates are the net effect of speciation and extinction, large genomes may thus either constrain speciation rate, increase extinction rate, or both. I argue that some of the cited examples are unlikely to be explained by extinction alone.     

Mass extinctions do not explain skew in interspecific body size distributions

In several higher animal taxa, such as mammals and birds, the distribution of species body sizes is heavily skewed towards small size. Previous studies have suggested that small‐bodied organisms are less prone to extinction than large‐bodied species. If small body size is favourable during mass extinction events, a post mass extinction excess of small‐bodied species may proliferate and maintain skewed body size distributions sometime after. Here, we modelled mass extinctions and found that even unrealistically strong body mass selection has little effect on the skew of interspecific body size distributions. Moreover, selection against large body size may, counter intuitively, skew size distributions towards large body size. In any case, subsequent evolutionary diversification rapidly erases these rather small effects mass extinctions may have on size distributions. Next, we used body masses of extant species and phylogenetic methods to investigate possible changes in body size distributions across the Cretaceous–Paleogene (K‐Pg) mass extinction. Body size distributions of extant clades that originated during the Cretaceous are on average more skewed than their subclades that originated during the Paleogene, but the difference is only minor in mammals, and in birds, it can be explained by a positive relationship between species richness and skewness that is also present in clades that originated after the transition. Hence, we cannot infer from extant species whether the K‐Pg mass extinctions were size‐selective, but they are not the reason why most extant bird and mammal species are small‐bodied.     

Defaunation and fragmentation erode small mammal diversity dimensions in tropical forests

Forest fragmentation and defaunation are considered the main drivers of biodiversity loss, yet the synergistic effects of landscape changes and biotic interactions on assemblage structure have been poorly investigated. Here, we use an extensive dataset of 283 assemblages and 105 species of small mammals to understand how defaunation of medium and large mammals and forest fragmentation change the community composition and diversity of rodents and marsupials in tropical forests of South America. We used structured equation models to investigate the relationship between small mammal species, functional and phylogenetic diversity with forest size, forest cover and the occurrence of medium and large mammals. The best‐fit model showed that defaunation reduced functional diversity, and that species diversity of small mammals increased with forest patch size. Forest cover did not affect functional and phylogenetic diversity. Our results indicate that occurrence of medium and large sized mammals (probably acting as predators, or competitors of small mammals) and forest patch size help to retain species and functional diversity in small mammal communities. Further, the number of species in a small mammal community was critical to the maintenance of phylogenetic diversity, and may have a pronounced influence on the ecological functions played by small mammals. Identifying how phylogenetic and functional diversity change in function of human pressures allows us to better understand the contribution of extant lineages to ecosystem functioning in tropical forests.     

Termites, Large Herbivores, and Herbaceous Plant Dominance Structure Small Mammal Communities in Savannahs

Large herbivores and termites are important functional groups in African savannahs. Both groups affect small mammals, which are also important determinants for savannah structure and function. Because vegetation on Macrotermes mounds are preferentially grazed by large herbivores, and mounds represent resource-rich distinct habitat patches for small mammals in relatively resource-poor savannahs, termite mounds are ideal sites for studies of how grazing by large mammals and productivity affect communities of small mammals. We conducted an experiment in Lake Mburo National Park, Uganda, with four treatments: large vegetated Macrotermes mounds (with and without large herbivores) and adjacent savannah areas (with and without large herbivores). We replicated the treatment blocks nine times and trapped small mammals regularly over a period of almost 2 years. Small mammal species assemblages differed considerably between mounds and savannah areas. Grazing had a substantial effect on small mammal species assemblages in the resource-poor savannah, but not in the relatively resource-rich termitaria. Small mammal species abundance, biomass, and richness were higher on termite mounds than adjacent savannah areas. Excluding large herbivores caused a major increase in species abundance, biomass, and richness both on savannah and termitaria. Herbaceous plant species evenness was an important determinant of the small mammal community. Small mammal biomass increased with high plant dominance, indicating that a few dominant plant species are important for biomass production of small mammals. Small mammal diversity was not related to any of the treatments, but increased with plant species evenness as well as richness. Fencing increased species dominance in the small mammal community on both savannah and termitaria, probably because competitive patterns shift from inter-guild (that is, between large and small mammals) to intra-guild (that is, between small mammals) when large mammals are excluded. The study highlights the complex interactions among large herbivores, termites, herbaceous plants, and small mammals in African savannahs. When studying the structure and function of small mammal communities it is therefore important to consider several coexisting functional groups.     

Minimal effects of latitude on present-day speciation rates in New World birds

The tropics contain far greater numbers of species than temperate regions, suggesting that rates of species formation might differ systematically between tropical and non-tropical areas. We tested this hypothesis by reconstructing the history of speciation in New World (NW) land birds using BAMM, a Bayesian framework for modelling complex evolutionary dynamics on phylogenetic trees. We estimated marginal distributions of present-day speciation rates for each of 2571 species of birds. The present-day rate of speciation varies approximately 30-fold across NW birds, but there is no difference in the rate distributions for tropical and temperate taxa. Using macroevolutionary cohort analysis, we demonstrate that clades with high tropical membership do not produce species more rapidly than temperate clades. For nearly any value of present-day speciation rate, there are far more species in the tropics than the temperate zone. Any effects of latitude on speciation rate are marginal in comparison to the dramatic variation in rates among clades.     

Detecting shifts in diversity limits from molecular phylogenies: what can we know?

Large complete species-level molecular phylogenies can provide the most direct information about the macroevolutionary history of clades having poor fossil records. However, extinction will ultimately erode evidence of pulses of rapid speciation in the deep past. Assessment of how well, and for how long, phylogenies retain the signature of such pulses has hitherto been based on a--probably untenable--model of ongoing diversity-independent diversification. Here, we develop two new tests for changes in diversification 'rules' and evaluate their power to detect sudden increases in equilibrium diversity in clades simulated with diversity-dependent speciation and extinction rates. Pulses of diversification are only detected easily if they occurred recently and if the rate of species turnover at equilibrium is low; rates reported for fossil mammals suggest that the power to detect a doubling of species diversity falls to 50 per cent after less than 50 Myr even with a perfect phylogeny of extant species. Extinction does eventually draw a veil over past dynamics, suggesting that some questions are beyond the limits of inference, but sudden clade-wide pulses of speciation can be detected after many millions of years, even when overall diversity is constrained. Applying our methods to existing phylogenies of mammals and angiosperms identifies intervals of elevated diversification in each.     

Exploring the phylogenetic history of mammal species richness

Aim At broad geographical scales, species richness is a product of three basic processes: speciation, extinction and migration. However, determining which of these processes predominates is a major challenge. Whilst palaeontological studies can provide information on speciation and extinction rates, data are frequently lacking. Here we use a recent dated phylogenetic tree of mammals to explore the relative importance of these three processes in structuring present‐day richness gradients. Location The global terrestrial biosphere. Methods We combine macroecological data with phylogenetic methods more typically used in community ecology to describe the phylogenetic history of regional faunas. Using simulations, we explore two simple phylogenetic metrics, the mean and variance in the pairwise distances between taxa, and describe their relationship to phylogenetic tree topology. We then use these two metrics to characterize the evolutionary relationships among mammal species assemblages across the terrestrial biome. Results We show that the mean and variance in the pairwise distances describe phylogenetic tree topology well, but are less sensitive to phylogenetic uncertainty than more direct measures of tree shape. We find the phylogeny for South American mammals is imbalanced and ‘stemmy’ (long branches towards the root), consistent with recent diversification within evolutionarily disparate lineages. In contrast, the phylogeny for African mammals is balanced and ‘tippy’ (long branches towards the tips), more consistent with the slow accumulation of diversity over long times, reflecting the Old World origin of many mammal clades. Main conclusions We show that phylogeny can accurately capture biogeographical processes operating at broad spatial scales and over long time periods. Our results support inferences from the fossil record – that the New World tropics are a diversity cradle whereas the Old World tropics are a museum of old diversity.     

Rapid allopatric speciation in logperch darters (Percidae: Percina)

Theory predicts that clades diversifying via sympatric speciation will exhibit high diversification rates. However, the expected rate of diversification in clades characterized by allopatric speciation is less clear. Previous studies have documented significantly higher speciation rates in freshwater fish clades diversifying via sympatric versus allopatric modes, leading to suggestions that the geographic pattern of speciation can be inferred solely from knowledge of the diversification rate. We tested this prediction using an example from darters, a clade of approximately 200 species of freshwater fishes endemic to eastern North America. A resolved phylogeny was generated using mitochondrial DNA gene sequences for logperches, a monophyletic group of darters composed of 10 recognized species. Divergence times among logperch species were estimated using a fossil calibrated molecular clock in centrarchid fishes, and diversification rates in logperches were estimated using several methods. Speciation events in logperches are recent, extending from 4.20 +/- 1.06 million years ago (mya) to 0.42 +/- 0.22 mya, with most speciation events occurring in the Pleistocene. Diversification rates are high in logperches, at some nodes exceeding rates reported for well-studied adaptive radiations such as Hawaiian silverswords. The geographic pattern of speciation in logperches was investigated by examining the relationship between degree of sympatry and the absolute age of the contrast, with the result that diversification in logperches appears allopatric. The very high diversification rate observed in the logperch phylogeny is more similar to freshwater fish clades thought to represent examples of sympatric speciation than to clades representing allopatric speciation. These results demonstrate that the geographic mode of speciation for a clade cannot be inferred from the diversification rate. The empirical observation of high diversification rates in logperches demonstrates that allopatric speciation can occur rapidly.     

Niche width impacts vertebrate diversification

Aim The size of the climatic niche of a species is a major factor determining its distribution and evolution. In particular, it has been proposed that niche width should be associated with the rate of species diversification. Here, we test whether species niche width affects the speciation and extinction rates of three main clades of vertebrates: amphibians, mammals and birds. Location Global. Methods We obtained the time‐calibrated phylogenies, IUCN conservation status, species distribution maps and climatic data for 2340 species of amphibians, 4563 species of mammals and 9823 species of birds. We computed the niche width for each species as the mean annual temperature across the species range. We estimated speciation, extinction and transition rates associated with lineages with either narrow (specialist) or wide (generalist) niches using phylogeny‐based birth–death models. We also tested if current conservation status was correlated with the niche width of species. Results We found higher net diversification rates in specialist species than in generalist species. This result was explained by both higher speciation rates (for the three taxonomic groups) and lower extinction rates (for mammals and birds only) in specialist than in generalist species. In contrast, current specialist species tended to be more threatened than generalist species. Main conclusions Our diversification analysis shows that the width of the climatic niche is strongly associated with diversification rates and may thus be a crucial factor for understanding the emergence of diversity patterns in vertebrates. The striking difference between our diversification results and current conservation status suggests that the current extinction process may be different from extinction rates estimated from the whole history of the group.     

Habitat preferences and biomasses of small mammals in Swaziland

This paper describes the distribution and abundance of small mammals in Swaziland in relation to quantified habitat features. Eighteen habitat sites were sampled at seven different locations in all four geographical regions of Swaziland. Small mammal diversity (as described by the Shannon diversity index) was positively correlated with vegetation density. A total of twelve species of rodents and seven species of shrews were captured; however, only six species were caught at more than three sites. Small mammal biomasses and densities were highest at the highveld and middleveld sites. Tall grassland at all elevations supported a high diversity of small mammals. Highveld montane forest supported a high biomass and diversity of species, while no species were captured in moist forest in the Lubombo mountains.     

Effects of roads on small mammal diversity and abundance in the northern Serengeti,Tanzania

The high biodiversity of small mammal species in the Serengeti ecosystem provides this ecosystem with important conservation value. However, whether the extensive development of roads has negative impacts on the small mammal population has not been tested. Small mammal population diversity and abundance were examined in this study using live trapping at sites close to (experimental) and away (control) from the main gravel road during the short rainy seasons in November and December 2011 and 2012. A total of 138 individuals from three orders representing six families and fourteen species were collected over 4,860 trap nights. There were no significant differences in the species richness, diversity or abundance of small mammals between the control and experimental sites (p > 0.05), suggesting that the current gravel road does not have a significant impact on the small mammal population. These findings were ascribed to the availability of favourable habitats at both distances as a result of little road usage due to poor conditions. Should the road be improved, the control of anthropogenic activities in the area should be given high priority. Continuous monitoring of the small mammal populations in the area is recommended.     

Species-range size distributions in Britain

The detailed forms of species-range size distributions in Britain are determined and contrasted for ten taxonomic assemblages (liverworts, vascular plants, molluscs [aquatic and terrestrial], dragonflies, macro-moths. butterflies, birds [breeding and wintering], mammals). All are strongly right-skewed when range sizes are untransformed. A logarithmic transformation fails to normalise the distribution for all but one group, and the distributions for several groups are not readily normalised at all. Taxa with larger median range sizes have species-range size distributions that are less strongly right-skewed. The median observed range sizes of species in each of the taxonomic groups fall, in terms of decreasing range size, in the sequence wintering birds < breeding birds < mammals < butterflies < terrestrial molluscs < dragonflies < aquatic molluscs < vascular plants < moths < liverworts. Despite the difficulties in deriving a simple and sensible mechanistic model for range size distributions, this is likely to be the most important next step towards understanding their forms.     

SPECIES DIVERSITY AND COMMUNITY STRUCTURE OF SUCKING LICE IN YUNNAN, CHINA

Abstract  On the basis of investigating 9 counties (towns) in Yunnan Province of China, the species diversity and community structure of sucking lice on the body surface of small mammal hosts are studied in the paper. Species richness ( S ) is used to stand for the species diversity. The calculation of community diversity index and evenness are based on Shannon-Wiener's method. 2 745 small mammals captured from the investigated sites belong to 10 families, 25 genera and 41 species in 5 orders (Rodentia, Insectivora, Scandentia, Logomorpha and Carnivora) while 18165 individuals of sucking lice collected from the body surface of the small mammal hosts are identified into 4 families, 6 genera and 22 species. The species of sucking lice are much less than the species of their hosts. Most species of small mammals have their fixed sucking lice on their body surface. One species of small mammals usually have few species of sucking lice (1 to 4 species). The close species of the hosts in the taxonomy are found to have the same or similar dominant species of sucking lice on their body surface. The results reveal that the species diversity of sucking lice on small mammals is very low with a very simple community structure. The results also imply there may be a close co-evolution relationship between the lice and the hosts.     

Maintenance of small mammals using post-harvest woody debris structures on clearcuts: linear configuration of piles is comparable to windrows

Management of post-harvest woody debris structures (e.g., piles and windrows) may help conserve mammal diversity in commercial forest landscapes. A windrow (continuous woody debris) provides a linear habitat to connect patches and reserves of uncut forest and riparian areas to maintain forest-floor small mammals and allow some of their avian and mammalian predators to access and traverse clearcut openings. However, most post-harvest residues are arranged in independent piles of woody debris (separated by 20–30 m, on average) and we asked if a linear configuration of piles would provide similar habitat conditions for small mammals as that achieved by a windrow of continuous woody debris. We tested two hypotheses (H) that piles of woody debris arranged in a linear configuration, on newly clearcut sites, would (H₁) enhance (a) abundance of the major small mammal species (Myodes gapperi and Microtus spp.), and (b) total abundance, species richness, and species diversity of the forest-floor small mammal community; compared with dispersed (conventional) treatment of woody debris. H₂ predicted that, because of the continuity of habitat, responses of small mammals in windrows would be greater than those in piles of woody debris. Three study areas were monitored in southern British Columbia, Canada, and each had three treatments of woody debris: dispersed, in a linear set of piles, and as a windrow. Forest-floor small mammals were sampled by live-trapping in spring and fall periods from 2010 to 2012. Woody debris in a linear configuration of piles and in windrows enhanced mean abundance of the southern red-backed vole (M. gapperi), total voles, and total abundance of small mammals compared with the dispersed treatment. Small mammal responses were variable between spring and fall periods, but overall mean values ± 95% CIs indicated that abundance of M. gapperi, total voles, and total small mammals were reasonably similar in piles and windrows.     

中国云南吸虱昆虫物种多样性及群落结构研究(英文)

在对云南省9个县(市)抽样调查的基础上,本文对境内小型哺乳动物(小兽)体表吸虱昆虫物种多样性及群落结构进行了研究。物种多样性用物种丰富度表示,多样性指数及均匀度计算采用Shannon-Wiener方法。所捕获的2745只小兽经分类鉴定隶属啮齿目、食虫目、攀目、兔形目和食肉目5个目中的10科、25属、41种。从各种小兽宿主体表共采集到吸虱昆虫18165只,经分类鉴定隶属4科、6属、22种,其种类明显少于宿主种类。几乎每种小兽宿主体表都有固定的吸虱种类寄生,但吸虱种类数很少(1-4种)。动物分类上接近的宿主,其体表的优势吸虱种类基本相同。研究结果表明,小型哺乳动物体表吸虱昆虫的物种多样性很低,群落结构十分简单。研究同时提示,吸虱昆虫与小兽宿主之间可能存在高度一致的协同进化关系。     

Ecological Interactions in Dinosaur Communities: Influences of Small Offspring and Complex Ontogenetic Life Histories

Because egg-laying meant that even the largest dinosaurs gave birth to very small offspring, they had to pass through multiple ontogenetic life stages to adulthood. Dinosaurs’ successors as the dominant terrestrial vertebrate life form, the mammals, give birth to live young, and have much larger offspring and less complex ontogenetic histories. The larger number of juveniles in dinosaur as compared to mammal ecosystems represents both a greater diversity of food available to predators, and competitors for similar-sized individuals of sympatric species. Models of population abundances across different-sized species of dinosaurs and mammals, based on simulated ecological life tables, are employed to investigate how differences in predation and competition pressure influenced dinosaur communities. Higher small- to medium-sized prey availability leads to a normal body mass-species richness (M-S) distribution of carnivorous dinosaurs (as found in the theropod fossil record), in contrast to the right-skewed M-S distribution of carnivorous mammals (as found living members of the order Carnivora). Higher levels of interspecific competition leads to a left-skewed M-S distribution in herbivorous dinosaurs (as found in sauropods and ornithopods), in contrast to the normal M-S distribution of large herbivorous mammals. Thus, our models suggest that differences in reproductive strategy, and consequently ontogeny, explain observed differences in community structure between dinosaur and mammal faunas. Models also show that the largest dinosaurian predators could have subsisted on similar-sized prey by including younger life stages of the largest herbivore species, but that large predators likely avoided prey much smaller than themselves because, despite predicted higher abundances of smaller than larger-bodied prey, contributions of small prey to biomass intake would be insufficient to satisfy meat requirements. A lack of large carnivores feeding on small prey exists in mammals larger than 21.5 kg, and it seems a similar minimum prey-size threshold could have affected dinosaurs as well.     

Large-scale phylogenetic analyses reveal the causes of high tropical amphibian diversity

Many groups show higher species richness in tropical regions but the underlying causes remain unclear. Despite many competing hypotheses to explain latitudinal diversity gradients, only three processes can directly change species richness across regions: speciation, extinction and dispersal. These processes can be addressed most powerfully using large-scale phylogenetic approaches, but most previous studies have focused on small groups and recent time scales, or did not separate speciation and extinction rates. We investigate the origins of high tropical diversity in amphibians, applying new phylogenetic comparative methods to a tree of 2871 species. Our results show that high tropical diversity is explained by higher speciation in the tropics, higher extinction in temperate regions and limited dispersal out of the tropics compared with colonization of the tropics from temperate regions. These patterns are strongly associated with climate-related variables such as temperature, precipitation and ecosystem energy. Results from models of diversity dependence in speciation rate suggest that temperate clades may have lower carrying capacities and may be more saturated (closer to carrying capacity) than tropical clades. Furthermore, we estimate strikingly low tropical extinction rates over geological time scales, in stark contrast to the dramatic losses of diversity occurring in tropical regions presently.     

Life on high: the diversity of small mammals at high altitude in South Africa

The Great Escarpment is the major mountain system in South Africa, yet very few biological surveys have been conducted outside of the well-known Drakensberg section. This is surprising given the important role that mountains play in local and global biodiversity patterns. In this study, small mammal diversity and community composition were estimated at three high altitude (>1,700?m) sites within the Sneeuberg Mountain Complex (SMC) of the Great Escarpment, South Africa from June 2009 to May 2010. The influences of selected environmental variables on diversity were also tested. Of 423 live-captures, a total of 292 unique individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were identified during 5,280 trap nights. No single environmental variable could account for the variation observed in diversity measurements but vegetation height appeared to be the most important factor to influence the number of individuals captured. It is hypothesised that the high species richness and diversity of small mammals observed in the SMC compared to other parts of the Great Escarpment is due to the SMC being located in a transition zone of the Grassland and Nama-Karoo biomes. Our results suggest that the SMC could be important in conserving small mammal species from western and eastern assemblages across South Africa.     

四川黑竹沟地区非飞行小型兽类物种多样性与群落组成

四川黑竹沟国家级自然保护区位于生物多样性丰富的凉山山系, 在保护和维持区域生物多样性方面具有极其重要的地位, 然而对该自然保护区兽类群落的研究却极为缺乏。为了了解该自然保护区及周边的小型兽类群落,本文作者在2018年4-10月调查了该区域的非飞行小型兽类物种多样性及其群落组成。在海拔1,537-3,830 m间共设置样方184个, 布设鼠夹9,016铗日, 捕获小型兽类536只, 隶属4目7科13属21种。包括滇攀鼠(Vernaya fulva)和等齿鼩鼹(Uropsilus aequodonenia)两个稀有物种在内的共计9个物种为该地区首次报道, 丰富了物种分布记录。结合历史资料, 黑竹沟地区共记录小型兽类43种, 隶属4目9科28属。在43种小型兽类中, 东洋界物种37种, 占绝对优势(86%), 分布型以喜马拉雅-横断山型占优, 为18种(占东洋界48.6%)。本次调查捕获的21种小型兽类中, 群落优势种为中华姬鼠(Apodemus draco, 33.2%)、北社鼠(Niviventer confucianus, 21.3%)和中华绒鼠(Eothenomys chinensis, 12.7%)。随着海拔上升, 群落优势种组成发生变化, 由北社鼠 + 中华姬鼠 + 针毛鼠(Niviventer fulvescens) + 短尾鼩(Anourosorex squamipes)群落, 转变为中华绒鼠 + 中华姬鼠 + 凉山沟牙田鼠(Proedromys liangshanensis) + 西南绒鼠(Eothenomys custos)群落。群落物种区系的分布型组成随着海拔升高而发生变化, 喜马拉雅-横断山型物种随海拔升高所占比例增大; 分布于喜马拉雅-横断山的特有种分布的下限、中点和上限平均海拔都高于非特有种, 且特有种和非特有种的中点和下限平均海拔差异显著(n = 21, df = 19, P = 0.013; n = 21, df = 19, P < 0.01), 说明该区域物种具有明显的东洋界特征, 中高海拔主要由特有种构成。本研究丰富了黑竹沟地区小型兽类及群落多样性的数据资料, 有利于该地区物种多样性的研究和保护。