Global drivers of population density in terrestrial vertebrates

Aim

Although the effects of life history traits on population density have been investigated widely, how spatial environmental variation influences population density for a large range of organisms and at a broad spatial scale is poorly known. Filling this knowledge gap is crucial for global species management and conservation planning and to understand the potential impact of environmental changes on multiple species.

Location

Global.

Time period

Present.

Major taxa studied

Terrestrial amphibians, reptiles, birds and mammals.

Methods

We collected population density estimates for a range of terrestrial vertebrates, including 364 estimates for amphibians, 850 for reptiles, 5,667 for birds and 7,651 for mammals. We contrasted the importance of life history traits and environmental predictors using mixed models and tested different hypotheses to explain the variation in population density for the four groups. We assessed the predictive accuracy of models through cross‐validation and mapped the partial response of vertebrate population density to environmental variables globally.

Results

Amphibians were more abundant in wet areas with high productivity levels, whereas reptiles showed relatively higher densities in arid areas with low productivity and stable temperatures. The density of birds and mammals was typically high in temperate wet areas with intermediate levels of productivity. The models showed good predictive abilities, with pseudo‐R² ranging between 0.68 (birds) and 0.83 (reptiles).

Main conclusions

Traits determine most of the variation in population density across species, whereas environmental conditions explain the intraspecific variation across populations. Species traits, resource availability and climatic stability have a different influence on the population density of the four groups. These models can be used to predict the average species population density over large areas and be used to explore macroecological patterns and inform conservation analyses.     

Fine‐scale quantification of floral and faunal breaks and their geographic correlates,with an example from south‐eastern Australia

Aim We introduce a method to quantify shared breaks in aggregate biotic distributions and their relationships to geographic variables. The method is based on quantification of distributional taxic and abiotic data that can be applied over multiple spatial scales. We aim to show biogeographic breaks and varying transition zones at a fine level of detail (5‐km resolution) and develop an approach to assess existing bioregionalization schemes. Location Global applicability, using an example from New South Wales in south‐eastern Australia. Methods Moving window analyses, rotated in 15° increments through 360°, are used to assess the degree of anisotropic spatial turnover between sets of gridded cells containing georeferenced species observations. Patterns of biotic turnover are compared with equivalent analyses for elevation and lithology. Identified breaks are assessed against an existing bioregionalization scheme (Interim Biogeographic Regionalisation of Australia, IBRA). Results There was fine‐scale concordance between turnover patterns and several IBRA bioregions. Breaks in turnover of flora and fauna corresponded with the boundaries of the Hunter Valley and Sydney Basin regions, particularly the boundary between the Brigalow Belt South and Sydney Basin. Low‐turnover zones were quantified; prominent examples are the Sydney Cataract and Wyong bioregions. Turnover along many boundaries was gradational, confirming that mapped breaks are not abrupt. A previously unidentified break was identified in the South East Corner bioregion. Spatial turnover patterns were similar between biota and were reflected in mean correlation coefficients between turnover in each group: mammals–reptiles (r = 0.70, P << 0.01); mammals–flora (r = 0.56, P << 0.01); and reptiles–flora (r = 0.51, P << 0.01). Generally, patterns of abiotic turnover reflected biotic turnover, although mean turnover correlations were weaker than between biota. Main conclusions Using this method we were able to characterize taxic breaks and overlaps in detail and at a spatially fine resolution. For our study region, we confirm the overall integrity of the IBRA framework, but suggest that it may benefit from revision in some respects.     

Unveiling the environmental drivers of intraspecific body size variation in terrestrial vertebrates

Aim

Whether intraspecific spatial patterns in body size are generalizable across species remains contentious, as well as the mechanisms underlying these patterns. Here we test several hypotheses explaining within-species body size variation in terrestrial vertebrates including the heat balance, seasonality, resource availability and water conservation hypotheses for ectotherms, and the heat conservation, heat dissipation, starvation resistance and resource availability hypotheses for endotherms.

Location

Global.

Time period

1970–2016.

Major taxa studied

Amphibians, reptiles, birds and mammals.

Methods

We collected 235,905 body size records for 2,229 species (amphibians = 36; reptiles = 81; birds = 1,545; mammals = 567) and performed a phylogenetic meta-analysis of intraspecific correlations between body size and environmental variables. We further tested whether correlations differ between migratory and non-migratory bird and mammal species, and between thermoregulating and thermoconforming ectotherms.

Results

For bird species, smaller intraspecific body size was associated with higher mean and maximum temperatures and lower resource seasonality. Size–environment relationships followed a similar pattern in resident and migratory birds, but the effect of resource availability on body size was slightly positive only for non-migratory birds. For mammals, we found that intraspecific body size was smaller with lower resource availability and seasonality, with this pattern being more evident in sedentary than migratory species. No clear size–environment relationships were found for reptiles and amphibians.

Main conclusions

Within-species body size variation across endotherms is explained by disparate underlying mechanisms for birds and mammals. Heat conservation (Bergmann's rule) and heat dissipation are the dominant processes explaining biogeographic intraspecific body size variation in birds, whereas in mammals, body size clines are mostly explained by the starvation resistance and resource availability hypotheses. Our findings contribute to a better understanding of the mechanisms behind species adaptations to the environment across their geographic distributions.     

Estimating hybridization in the presence of coalescence using phylogenetic intraspecific sampling

Background

Recent research has indicated a positive association between rates of molecular evolution and diversification in a number of taxa. However debate continues concerning the universality and cause of this relationship. Here, we present the first systematic investigation of this relationship within the mammals. We use phylogenetically independent sister-pair comparisons to test for a relationship between substitution rates and clade size at a number of taxonomic levels. Total, non-synonymous and synonymous substitution rates were estimated from mitochondrial and nuclear DNA sequences.

Results

We found no evidence for an association between clade size and substitution rates in mammals, for either the nuclear or the mitochondrial sequences. We found significant associations between body size and substitution rates, as previously reported.

Conclusions

Our results present a contrast to previous research, which has reported significant positive associations between substitution rates and diversification for birds, angiosperms and reptiles. There are three possible reasons for the differences between the observed results in mammals versus other clades. First, there may be no link between substitution rates and diversification in mammals. Second, this link may exist, but may be much weaker in mammals than in other clades. Third, the link between substitution rates and diversification may exist in mammals, but may be confounded by other variables.     

The evolution of pepsinogen C genes in vertebrates: duplication, loss and functional diversification

Background

Aspartic proteases comprise a large group of enzymes involved in peptide proteolysis. This collection includes prominent enzymes globally categorized as pepsins, which are derived from pepsinogen precursors. Pepsins are involved in gastric digestion, a hallmark of vertebrate physiology. An important member among the pepsinogens is pepsinogen C (Pgc). A particular aspect of Pgc is its apparent single copy status, which contrasts with the numerous gene copies found for example in pepsinogen A (Pga). Although gene sequences with similarity to Pgc have been described in some vertebrate groups, no exhaustive evolutionary framework has been considered so far.

Methodology/Principal Findings

By combining phylogenetics and genomic analysis, we find an unexpected Pgc diversity in the vertebrate sub-phylum. We were able to reconstruct gene duplication timings relative to the divergence of major vertebrate clades. Before tetrapod divergence, a single Pgc gene tandemly expanded to produce two gene lineages (Pgbc and Pgc2). These have been differentially retained in various classes. Accordingly, we find Pgc2 in sauropsids, amphibians and marsupials, but not in eutherian mammals. Pgbc was retained in amphibians, but duplicated in the ancestor of amniotes giving rise to Pgb and Pgc1. The latter was retained in mammals and probably in reptiles and marsupials but not in birds. Pgb was kept in all of the amniote clade with independent episodes of loss in some mammalian species. Lineage specific expansions of Pgc2 and Pgbc have also occurred in marsupials and amphibians respectively. We find that teleost and tetrapod Pgc genes reside in distinct genomic regions hinting at a possible translocation.

Conclusions

We conclude that the repertoire of Pgc genes is larger than previously reported, and that tandem duplications have modelled the history of Pgc genes. We hypothesize that gene expansion lead to functional divergence in tetrapods, coincident with the invasion of terrestrial habitats.     

Short-wavelength sensitive opsin (SWS1) as a new marker for vertebrate phylogenetics

Background  

Vertebrate SWS1 visual pigments mediate visual transduction in response to light at short wavelengths. Due to their importance in vision, SWS1 genes have been isolated from a surprisingly wide range of vertebrates, including lampreys, teleosts, amphibians, reptiles, birds, and mammals. The SWS1 genes exhibit many of the characteristics of genes typically targeted for phylogenetic analyses. This study investigates both the utility of SWS1 as a marker for inferring vertebrate phylogenetic relationships, and the characteristics of the gene that contribute to its phylogenetic utility.     

An exploration of differences in the scaling of life history traits with body mass within reptiles and between amniotes

Allometric relationships linking species characteristics to body size or mass (scaling) are important in biology. However, studies on the scaling of life history traits in the reptiles (the nonavian Reptilia) are rather scarce, especially for the clades Crocodilia, Testudines, and Rhynchocephalia (single extant species, the tuatara). Previous studies on the scaling of reptilian life history traits indicated that they differ from those seen in the other amniotes (mammals and birds), but so far most comparative studies used small species samples and also not phylogenetically informed analyses. Here, we analyzed the scaling of nine life history traits with adult body mass for crocodiles (n = 22), squamates (n = 294), turtles (n = 52), and reptiles (n = 369). We used for the first time a phylogenetically informed approach for crocodiles, turtles, and the whole group of reptiles. We explored differences in scaling relationships between the reptilian clades Crocodilia, Squamata, and Testudines as well as differences between reptiles, mammals, and birds. Finally, we applied our scaling relationships, in order to gain new insights into the degree of the exceptionality of the tuatara's life history within reptiles. We observed for none of the life history traits studied any difference in their scaling with body mass between squamates, crocodiles, and turtles, except for clutch size and egg weight showing small differences between these groups. Compared to birds and mammals, scaling relationships of reptiles were similar for time‐related traits, but they differed for reproductive traits. The tuatara's life history is more similar to that of a similar‐sized turtle or crocodile than to a squamate.     

Potential effects of future climate change on global reptile distributions and diversity

Aim

Until recently, complete information on global reptile distributions has not been widely available. Here, we provide the first comprehensive climate impact assessment for reptiles on a global scale.

Location

Global, excluding Antarctica.

Time period

1995, 2050 and 2080.

Major taxa studied

Reptiles.

Methods

We modelled the distribution of 6296 reptile species and assessed potential global and realm-specific changes in species richness, the change in global species richness across climate space, and species-specific changes in range extent, overlap and position under future climate change. To assess the future climatic impact on 3768 range-restricted species, which could not be modelled, we compared the future change in climatic conditions between both modelled and non-modelled species.

Results

Reptile richness was projected to decline significantly over time, globally but also for most zoogeographical realms, with the greatest decreases in Brazil, Australia and South Africa. Species richness was highest in warm and moist regions, with these regions being projected to shift further towards climate extremes in the future. Range extents were projected to decline considerably in the future, with a low overlap between current and future ranges. Shifts in range centroids differed among realms and taxa, with a dominant global poleward shift. Non-modelled species were significantly stronger affected by projected climatic changes than modelled species.

Main conclusions

With ongoing future climate change, reptile richness is likely to decrease significantly across most parts of the world. This effect, in addition to considerable impacts on species range extent, overlap and position, was visible across lizards, snakes and turtles alike. Together with other anthropogenic impacts, such as habitat loss and harvesting of species, this is a cause for concern. Given the historical lack of global reptile distributions, this calls for a re-assessment of global reptile conservation efforts, with a specific focus on anticipated future climate change.     

Deconstructing the dimensions of alpha diversity in squamate reptiles (Reptilia: Squamata) across the Americas

Aim

Our aim is to document the dimensions of current squamate reptile biodiversity in the Americas by integrating taxonomic, phylogenetic and functional data, and assessing how this may vary across phylogenetic scales. We also explore the potential underlying mechanisms that may be responsible for the observed geographical diversity patterns.

Location

The Americas.

Time period

Present.

Major taxa

Squamate reptiles.

Methods

We used published data on the distribution, phylogeny, and body size of squamate reptiles to document the current dimensions of their alpha diversity in the Americas. We overlapped species ranges to estimate taxonomic diversity (TD) and calculated phylogenetic diversity (PD) using mean pairwise phylogenetic distance (MPD), speciation rate (DivRate) and Faith's phylogenetic index (PD). We estimated functional diversity (FD) as trait dispersion in the multivariate space using body size and leg development data. We implemented a deconstructive macroecological approach to understand how spatial mismatches between the three facets of diversity vary across phylogenetic scales, and the potential eco-evolutionary mechanisms driving these patterns across space.

Results

We found a strong latitudinal gradient of TD with a large accumulation in tropical regions. PD and FD patterns were largely similar likely due to the high phylogenetic signal in the traits used, and higher values tended to be concentrated in harsh and/or heterogeneous environments. We found differences between major clades within Squamata that display contrasting geographical patterns. Several regions across the continent shared the same spatial mismatches between dimensions across clades, suggesting that similar eco-evolutionary processes are shaping these regional reptile assemblages. However, we also found evidence that non-mutually exclusive processes can operate differently across clades.

Main conclusions

The deconstructive approach implemented here is based on a solid macroecological framework. We can extend this to other taxonomic groups to establish whether there are particularities about how different eco-evolutionary mechanisms shape biodiversity facets in a spatially explicit context.     

Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii : comparison of evolution of these toxins in land snakes, sea kraits and sea snakes

Background  

Snake venom composition varies widely both among closely related species and within the same species, based on ecological variables. In terrestrial snakes, such variation has been proposed to be due to snakes' diet. Land snakes target various prey species including insects (arthropods), lizards (reptiles), frogs and toads (amphibians), birds (aves), and rodents (mammals), whereas sea snakes target a single vertebrate class (fishes) and often specialize on specific types of fish. It is therefore interesting to examine the evolution of toxins in sea snake venoms compared to that of land snakes.     

中国大中型陆栖哺乳动物地理区边界探测及其驱动因素

地理隔离是驱动物种空间分布格局形成的主要原因之一。利用我国大中型陆栖哺乳动物的地理分布数据,基于信息地图生物区(Infomap Bioregions)方法探测生物地理区域,提取对大中型陆栖哺乳动物类群的分布扩散产生阻隔效应的主要界线。从温度、降水和地形的梯度变化角度入手,应用空间自回归模型确定与生物地理区边界相关的主要驱动因子,构建地理加权逻辑回归(GWLR)模型分析各驱动因子重要性的空间非平稳性特征。结果表明,研究区域划分为3个主要的生物地理区,除年降水量变异系数与边界联系不明显外,其余变量均在10%及以下的显著性水平与生物地理区边界呈正相关,反映出生物地理区边界与气候突变、地形障碍和人类活动的协同作用有关。生物地理区1与生物地理区3的边界线的主导影响因子是人类足迹指数,生物地理区1和生物地理区2的边界线的主导影响因子是气温季节性变动系数变异系数,生物地理区2和生物地理区3边界线在祁连山脉一带的主导影响因子主要是气温季节性变动系数变异系数,其余地区为地形障碍。多类群物种对隔离屏障的响应模式难以统一,研究从大中型动物入手,通过识别以不同物种组合为特征的生物地理区域,揭示物种在空间上的分组方式,为探讨各动物类群的隔离机制提供空间模式和框架。     

Evolutionary diversification of the vertebrate transferrin multi-gene family

In a phylogenetic analysis of vertebrate transferrins (TFs), six major clades (subfamilies) were identified: (a) S, the mammalian serotransferrins; (b) ICA, the mammalian inhibitor of carbonic anhydrase (ICA) homologs; (c) L, the mammalian lactoferrins; (d) O, the ovotransferrins of birds and reptiles; (e) M, the melanotransferrins of bony fishes, amphibians, reptiles, birds, and mammals; and (f) M-like, a newly identified TF subfamily found in bony fishes, amphibians, reptiles, and birds. A phylogenetic tree based on the joint alignment of N-lobes and C-lobes supported the hypothesis that three separate events of internal duplication occurred in vertebrate TFs: (a) in the common ancestor of the M subfamily, (b) in the common ancestor of the M-like subfamily, and (c) in the common ancestor of other vertebrate TFs. The S, ICA, and L subfamilies were found only in placental mammals, and the phylogenetic analysis supported the hypothesis that these three subfamilies arose by gene duplication after the divergence of placental mammals from marsupials. The M-like subfamily was unusual in several respects, including the presence of a uniquely high proportion of clade-specific conserved residues, including distinctive but conserved residues in the sites homologous to those functioning in carbonate binding of human serotransferrin. The M-like family also showed an unusually high proportion of cationic residues in the positively charged region corresponding to human lactoferrampin, suggesting a distinctive role of this region in the M-like subfamily, perhaps in antimicrobial defense.     

Data uncertainty and the selectivity of extinction risk in freshwater invertebrates

Aim

To investigate the impact of different treatments of the IUCN Data Deficient (DD) category on taxonomic and geographical patterns of extinction risk in crayfish, freshwater crabs and dragonflies.

Location

Global.

Methods

We used contingency tables to evaluate taxonomic and geographical selectivity of data deficiency and extinction risk for three invertebrate taxonomic groups (crayfish, dragonflies and damselflies, and freshwater crabs) based on their IUCN Red List status. We investigated differences in patterns of data deficiency and extinction risk among taxonomic families, geographical realms and taxonomic families within geographical realms for each of the three groups. At each level, we evaluated the impact of uncertainty conferred by the conservation status of DD species on extinction risk patterns exhibited by that group. We evaluated three scenarios: excluding DD species, treating all DD species as non‐threatened and treating all DD species as threatened.

Results

At the global scale, DD species were taxonomically non‐randomly distributed in freshwater crabs and dragonflies, and geographically non‐randomly distributed in all three taxonomic groups. Although the presence of under‐ or over‐threatened families and biogeographical realms was generally unchanging across scenarios, the strength of taxonomic and geographical selectivity of extinction risk varied. There was little consistent evidence for taxonomic selectivity of extinction risk at sub‐global scales in freshwater crabs and dragonflies, either among biogeographical realms or among scenarios.

Main conclusions

Global patterns of taxonomic selectivity and geographical selectivity were generally consistent with one another and robust to different treatments of DD species. However, sub‐global scale conservation prioritization from these types of data sets will require increased investment to make accurate decisions. Given the current levels of data uncertainty, the relative importance of biological characteristics and threatening processes in driving extinctions in freshwater invertebrates cannot be easily determined. We recommend that DD species should be given high research priority to determine their true status.     

Evolutionary and ecological success is decoupled in mammals

Aim

To identify which factors distinguish ecologically successful mammalian clades (i.e., clades with a large combined range size) from less successful ones.

Location

Global.

Methods

We estimated the total range sizes for each individual mammalian subfamily and used phylogenetic regressions to identify the relative importance of factors related to colonization ability (body size and niche width) and adaptability (rate of evolution of body size and rate of evolution of climatic preference) in determining these ranges. We then estimated the importance of the same factors on the variation in diversification rate within mammals.

Results

We found strong support for a link between total range size and traits related to colonization ability. In particular, we found larger total range sizes among clades containing larger bodied species and clades with wider climatic niche width, while we did not find support for any predictors related to adaptability being linked to total range size. We also found that traits related to increased range size were associated with reduced diversification rate.

Main Conclusions

Range size for mammalian clades is mainly predicted by colonization ability, suggesting that most clades are limited by dispersal rather than their ability to adapt to new environments. The most ecologically successful (i.e., most widespread) mammalian clades tend to possess traits that reduce geographical isolation among populations, but the same traits tend to decrease diversification rates. Our results unveil a decoupling between evolutionary and ecological success in mammals.

     

Biogeographic patterns of the East African coastal forest vertebrate fauna

The archipelago-like coastal forest of East Africa is one of the highest priority ecosystems for biodiversity conservation worldwide. Here we investigate patterns of species richness and biogeographic distribution among birds, mammals and reptiles of these forests, using distribution data obtained from recently published reviews and information collated by the WWF Eastern Africa Coastal Forest Ecoregion Programme. Birds and mammals species were divided into forest specialists and generalists, and forest specialist reptiles into ‘coastal’ and ‘forest’ endemics. The species richness of birds and generalist mammals increased with area, and is probably a result of area-dependent extinction. Only in birds, however, species richness increased with decreasing isolation, suggesting possible isolation-dependent colonization. Forest diversity, associated to altitudinal range, is important for specialist birds and mammals, whose species richness increased with wider altitudinal range. The number of relict coastal endemic and forest endemic reptiles was higher in forests with wider altitudinal ranges and on relatively higher altitude, respectively. Such forests have probably provided a suitable (and perhaps stable) environment for these species through time, thus increasing their persistence. Parsimony analysis of distributions (PAD) and cluster analyses showed geographical distance and general ecological similarity among forests as a determinant factor in bird distribution patterns, with compositional similarity decreasing with increasing inter-forest distance. Compositional similarity patterns of mammals among the forests did not show a strong geographical correspondence or a significant correlation with inter-forest distance, and those of reptiles were not resolved, with very low similarity levels among forest faunas. Our results suggest that the relative importance (and causal relationship) of forest attributes affecting the distribution of the East African coastal forest vertebrate fauna varies depending on life history traits such as dispersal ability and forest specialization. The groupings in PAD are partly congruent with some of the previous classifications of areas of endemism for this region, supporting the ‘naturalness’ of these regions.     

Biogeographical network analysis of plant species distribution in the Mediterranean region

The delimitation of bioregions helps to understand historical and ecological drivers of species distribution. In this work, we performed a network analysis of the spatial distribution patterns of plants in south of France (Languedoc‐Roussillon and Provence‐Alpes‐Côte d'Azur) to analyze the biogeographical structure of the French Mediterranean flora at different scales. We used a network approach to identify and characterize biogeographical regions, based on a large database containing 2.5 million of geolocalized plant records corresponding to more than 3,500 plant species. This methodology is performed following five steps, from the biogeographical bipartite network construction to the identification of biogeographical regions under the form of spatial network communities, the analysis of their interactions, and the identification of clusters of plant species based on the species contribution to the biogeographical regions. First, we identified two sub‐networks that distinguish Mediterranean and temperate biota. Then, we separated eight statistically significant bioregions that present a complex spatial structure. Some of them are spatially well delimited and match with particular geological entities. On the other hand, fuzzy transitions arise between adjacent bioregions that share a common geological setting, but are spread along a climatic gradient. The proposed network approach illustrates the biogeographical structure of the flora in southern France and provides precise insights into the relationships between bioregions. This approach sheds light on ecological drivers shaping the distribution of Mediterranean biota: The interplay between a climatic gradient and geological substrate shapes biodiversity patterns. Finally, this work exemplifies why fragmented distributions are common in the Mediterranean region, isolating groups of species that share a similar eco‐evolutionary history.     

Conservation biogeography of the Antarctic

Aim

To present a synthesis of past biogeographic analyses and a new approach based on spatially explicit biodiversity information for the Antarctic region to identify biologically distinct areas in need of representation in a protected area network.

Location

Antarctica and the sub‐Antarctic.

Methods

We reviewed and summarized published biogeographic studies of the Antarctic. We then developed a biogeographic classification for terrestrial conservation planning in Antarctica by combining the most comprehensive source of Antarctic biodiversity data available with three spatial frameworks: (1) a 200‐km grid, (2) a set of areas based on physical parameters known as the environmental domains of Antarctica and (3) expert‐defined bioregions. We used these frameworks, or combinations thereof, together with multivariate techniques to identify biologically distinct areas.

Results

Early studies of continental Antarctica typically described broad bioregions, with the Antarctic Peninsula usually identified as biologically distinct from continental Antarctica; later studies suggested a more complex biogeography. Increasing complexity also characterizes the sub‐Antarctic and marine realms, with differences among studies often attributable to the focal taxa. Using the most comprehensive terrestrial data available and by combining the groups formed by the environmental domains and expert‐defined bioregions, we were able to identify 15 biologically distinct, ice‐free, Antarctic Conservation Biogeographic Regions (ACBRs), encompassing the continent and close lying islands.

Main conclusions

Ice‐free terrestrial Antarctica comprises several distinct bioregions that are not fully represented in the current Antarctic Specially Protected Area network. Biosecurity measures between these ACBRs should also be developed to prevent biotic homogenization in the region.     

Historical and contemporary processes drive global phylogenetic structure across geographical scales: Insights from bat communities

Aim

Patterns of evolutionary relatedness among co-occurring species are driven by scale-dependent contemporary and historical processes. Yet, we still lack a detailed understanding of how these drivers impact the phylogenetic structure of biological communities. Here, we focused on bats (one of the most species-rich and vagile groups of mammals) and tested the predictions of three general biogeographical hypotheses that are particularly relevant to understanding how palaeoclimatic stability, local diversification rates and geographical scales shaped their present-day phylogenetic community structure.

Location

World-wide, across restrictive geographical extents: global, east–west hemispheres, biogeographical realms, tectonic plates, biomes and ecoregions.

Time period

Last Glacial Maximum (~22,000 years ago) to the present.

Major taxa studied

Bats (Chiroptera).

Methods

We estimated bat phylogenetic community structure across restrictive geographical extents and modelled it as a function of palaeoclimatic stability and in situ net diversification rates.

Results

Limiting geographical extents from larger to smaller scales greatly changed the phylogenetic structure of bat communities. The magnitude of these effects is less noticeable in the western hemisphere, where frequent among-realm biota interchange could have been maintained through the adaptive traits of bats. Bat communities with high phylogenetic relatedness are generally more common in regions that have changed less in climate since the Last Glacial Maximum, supporting the expectation that stable climates allow for increased phylogenetic clustering. Finally, increased in situ net diversification rates are associated with greater phylogenetic clustering in bat communities.

Main conclusions

We show that the world-wide phylogenetic structure of bat assemblages varies as a function of geographical extents, dispersal barriers, palaeoclimatic stability and in situ diversification. The integrative framework used in our study, which can be applied to other taxonomic groups, has not only proved useful to explain the evolutionary dynamics of community assembly, but could also help to tackle questions related to scale dependence in community ecology and biogeography.