Ecological traits influence the phylogenetic structure of bird species co‐occurrences worldwide

The extent to which species’ ecological and phylogenetic relatedness shape their co‐occurrence patterns at large spatial scales remains poorly understood. By quantifying phylogenetic assemblage structure within geographic ranges of >8000 bird species, we show that global co‐occurrence patterns are linked – after accounting for regional effects – to key ecological traits reflecting diet, mobility, body size and climatic preference. We found that co‐occurrences of carnivorous, migratory and cold‐climate species are phylogenetically clustered, whereas nectarivores, herbivores, frugivores and invertebrate eaters tend to be more phylogenetically overdispersed. Preference for open or forested habitats appeared to be independent from the level of phylogenetic clustering. Our results advocate for an extension of the tropical niche conservatism hypothesis to incorporate ecological and life‐history traits beyond the climatic niche. They further offer a novel species‐oriented perspective on how biogeographic and evolutionary legacies interact with ecological traits to shape global patterns of species coexistence in birds.     

Is high species richness at intermediate disturbance level valuable for phylogenetic conservation? A test on bird species in South‐East Botswana

The intermediate disturbance hypothesis (IDH) is one of the most debated theories in ecology. However, even when evidence is provided to support the hypothesis, its relevance for phylogenetic conservation has rarely been tested. Here, we investigated this question on birds in the South‐East district of Botswana along a disturbance gradient across three types of landscapes. We first reconstructed the phylogeny for all species recorded. Next, we assessed the relationship between dissimilarity measures and habitat types using the permutational MANOVA. Finally, we tested the IDH by fitting a generalized linear mixed effect model to account for errors due to spatial pseudo‐replications of our collection design. We found that, although species richness and phylogenetic diversity (PD) follow the prediction of the IDH, the evolutionary component of PD (i.e. PSV, phylogenetic species variability) contributes little to the prediction, suggesting that the correlation between PD and disturbance level is driven by the richness component of PD (i.e. PSR, phylogenetic species richness). However, the increased richness at the intermediate disturbance level does not result in phylogenetically diverse bird communities, indicating that the IDH contributes little to phylogenetic diversity. Our study adds to the body of literature questioning the relevance of IDH in ecology.     

Thermal performance of squamate embryos with respect to climate,adult life history,and phylogeny

Reptiles are important model systems for examining the effect of temperature during development on the phenotype of individuals after hatching or birth. To assess whether squamate embryos exhibit adaptive variation in thermal biology, we derived three parameters: an index of developmental rate (DRI), the upper thermal limit for successful incubation, and the lower thermal limit for development for 28 species of lizard and 12 species of snake. The associations between developmental parameters and climatic and life‐history variables were examined using both conventional statistics and phylogenetically controlled analyses. Residual DRI (i.e. DRI corrected for stage at oviposition and hatchling mass) was strongly associated with phylogenetic relationship. By contrast, the upper limit for development was negatively related to the amount of precipitation during the warmest quarter of the year, and the lower thermal limit for development was positively related to temperature during the warmest quarter of the year and the activity body temperatures of adults. These latter observations indicate that embryonic thermal physiology is adapted to large‐scale environmental patterns, and that global climate change will impact embryonic development directly through impacts on nest temperature per se, as well as indirectly through impacts on the ability of gravid females to select suitable nest sites. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Evolutionary constraints on regional faunas: whom, but not how many

The latitudinal diversity gradient has been hypothesized to reflect past evolutionary dynamics driven by climatic niche conservation during cladogenesis, i.e. the tropical conservatism hypothesis. Here we show that the species diversity of treefrogs (Hylidae) across the western hemisphere is actually independent of evolutionary niche dynamics. We evaluated three key predictions of the tropical conservatism hypothesis that relate to the relationships between climate, species richness and the phylogenetic structure of regional treefrog faunas across the continental Americas. Species composition was dependent on the inability of some lineages to evolve cold tolerance, but the actual number of species in a region was strongly predicted by precipitation, not temperature. Moreover, phylogenetic structure was independent of precipitation. Thus, species in low-richness areas were no more closely related than species in highly diverse regions. These results provide no support for the tropical conservatism hypothesis. Instead, they show that regional species composition and richness are constrained by different climatic components, demonstrating that global biodiversity gradients can be independent of niche stasis during cladogenesis.     

Disentangling the effects of intraspecies variability,phylogeny, space,and climate on the evolution of shell morphology in endemic Greek land snails of the genus Codringtonia

Extensive variation in land snail shell morphology has been widely documented, although few studies have attempted to investigate the ecological and evolutionary drivers of this variation. Within a comparative phylogenetic framework, we investigated the temporal and spatial evolution of the shell morphology of the Greek endemic land snail genus Codringtonia. The contribution of both inter‐ and intraspecies shell differentiation in the overall shell variability is assessed. The effect of climate, space, and evolutionary history on the shell variability was inferred using a variance partitioning framework. For Codringtonia species, intraspecies divergence of shell traits contributes substantially to the overall shell variability. By decomposing this variability, it was shown that the overall shell size of Codringtonia clades is phylogenetically constrained, related to early speciation events, and strongly affected by large‐scale spatial variability (latitudinal gradient). The effect of climate on shell size cannot be disentangled from phylogeny and space. Shell and, to a larger extent, aperture shape are not phylogenetically constrained, and appear to be mostly related to conspecific populations divergence events. Shell shape is substantially explained by both climate and space that greatly overlap. Aperture shape is mainly interpreted by medium to small‐scale spatial variables. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 796–813.     

The evolution of waving displays in fiddler crabs (Uca spp., Crustacea: Ocypodidae)

Male fiddler crabs are commonly recognized by the presence of a single massive claw used in a variety of contexts, including territorial defence, agonistic interactions, and courtship behaviour. The most common behavioural context involving these enlarged chelipeds is their use in waving displays, which are remarkably diverse among species. Although the waving display is one of the most obvious behavioural features of male fiddler crabs, little is known about their main evolutionary trends during the diversification of the genus. The present study employed phylogenetic comparative methods to investigate the evolution of waving behaviour in a sample of 19 species of Uca from Central and North America. Digital recordings were used to quantify the temporal dynamics of waving behaviour in each species. Multivariate ordination methods were used to assess whether different elements of the display showed distinct evolutionary dynamics, particularly with respect to body size and the environment where species are most commonly found. Most of the interspecific variation in displays involves differences in the overall waving velocity, with no correspondence to their local environments, nor their body size. Interestingly, despite the strong concentration of variance in the first two ordination axes, there was no statistically significant evidence for phylogenetic signals in their respective scores. These results suggest that the overall structure of waving displays is evolutionarily labile, at the same time as being concentrated in a few particular axes of variation, possibly indicating evolution along lines of least resistance. The approach employed in the present study highlights the utility of phylogenetic comparative methods for elucidating the evolution of complex behavioural characteristics, such as the waving display in male fiddler crabs. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 307–315.     

Altitudinal biodiversity patterns of seed plants along Gongga Mountain in the southeastern Qinghai–Tibetan Plateau

The mechanisms underlying elevation patterns in species and phylogenetic diversity remain a central issue in ecology and are vital for effective biodiversity conservation in the mountains. Gongga Mountain, located in the southeastern Qinghai–Tibetan Plateau, represents one of the longest elevational gradients (ca. 6,500 m, from ca. 1,000 to 7,556 m) in the world for studying species diversity patterns. However, the elevational gradient and conservation of plant species diversity and phylogenetic diversity in this mountain remain poorly studied. Here, we compiled the elevational distributions of 2,667 native seed plant species occurring in Gongga Mountain, and estimated the species diversity, phylogenetic diversity, species density, and phylogenetic relatedness across ten elevation belts and five vegetation zones. The results indicated that species diversity and phylogenetic diversity of all seed plants showed a hump‐shaped pattern, peaking at 1,800–2,200 m. Species diversity was significantly correlated with phylogenetic diversity and species density. The floras in temperate coniferous broad‐leaved mixed forests, subalpine coniferous forests, and alpine shrublands and meadows were significantly phylogenetically clustered, whereas the floras in evergreen broad‐leaved forests had phylogenetically random structure. Both climate and human pressure had strong correlation with species diversity, phylogenetic diversity, and phylogenetic structure of seed plants. Our results suggest that the evergreen broad‐leaved forests and coniferous broad‐leaved mixed forests at low to mid elevations deserve more conservation efforts. This study improves our understanding on the elevational gradients of species and phylogenetic diversity and their determinants and provides support for improvement of seed plant conservation in Gongga Mountain.     

Macroevolution and climate change influence phylogenetic community assembly of North American hoofed mammals

Animal richness, community composition, and phylogenetic community structure (PCS) vary across the modern landscape. Animal communities vary from phylogenetically clustered (i.e. higher relatedness amongst co‐occurring species than is expected by chance) to phylogenetically even (i.e. co‐occurring taxa are more distantly related than expected by chance), which is explained by abiotic or climatic filtering and competitive exclusion, respectively. Under this model, the contribution of historical origination and extinction events to modern animal PCS remains relatively unknown. Because origination and extinction determine the make‐up of the terrestrial community, the study of historical changes in animal PCS is tantamount to understanding formation of modern communities. In the present study, we test the effects of macroevolution and climate changes on ‘hoofed mammals’ (i.e. perissodactyl and artiodactyl) PCS from the late Cenozoic of North America because they experience large, phylogenetically dispersed extinctions of browsing species and phylogenetically dispersed originations of grazing species associated with the evolution of grassland ecosystems during the late Miocene. We show that the loss of numerically dominant nonhypsodont (putatively browsing and mixed feeding) clades and phylogenetically dispersed origination of less speciose clades following the mid Miocene climatic optimum led to an increase in phylogenetic evenness at the regional scale that is well explained by global climate changes. Phylogenetic evenness and a reduced richness during the late Cenozoic may have facilitated reduced niche overlap among co‐occurring hoofed mammal species as global climates cooled. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 485–494.     

Inferring the evolutionary history of divergence despite gene flow in a lizard species,Scincella lateralis (Scincidae), composed of cryptic lineages

Although recent radiations are fruitful for studying the process of speciation, they are difficult to characterize and require the use of multiple loci and analytical methods that account for processes such as gene flow and genetic drift. Using multilocus sequence data, we combine hierarchical cluster analysis, coalescent species tree inference, and isolation‐with‐migration analysis to investigate evolutionary relationships among cryptic lineages of North American ground skinks. We also estimate the extent that gene flow has accompanied or followed diversification, and also attempt to account for and minimize the influence of gene flow when reconstructing relationships. The data best support seven largely parapatric populations that are broadly concordant with mitochondrial (mt)DNA phylogeography throughout most of the species range, although they fail to fully represent extensive mtDNA divergence along the Gulf Coast. Relationships within and among three broad geographical groups are well supported, despite evidence of gene flow among them. Rejection of an allopatric divergence model partially depends on the inclusion of samples from near parapatric boundaries in the analyses, suggesting that allopatric divergence followed by recent migration may best explain migration rate estimates. Accounting for geographical variation in patterns of gene flow can improve estimates of migration–divergence parameters and minimize the influence of contemporary gene flow on phylogenetic inference. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Long‐distance call evolution in the Felidae: effects of body weight,habitat, and phylogeny

Long‐distance calls used for mate attraction and territorial spacing are distinctive signals in the felid vocal repertoire. Their evolution is subject to natural and sexual selection, as well as various constraints. Body size is an important morphological constraint, with the scaling of the spectral characteristics of a species' vocalizations with its body size being established for several vertebrate groups. Alternatively, the structure of long‐distance calls may have been optimized for transmission in species' habitats (acoustic adaptation hypothesis). The present study assessed whether the mean dominant frequency of long‐distance calls in the Felidae (approximately 70% of all species incorporated) is influenced by the species' body size and/or conforms to the acoustic adaptation hypothesis. After controlling for phylogenetic relationships, we found a significant correlation between mean dominant frequency of a taxon's long‐distance calls and conditions for sound transmission in its habitat type (‘open/heterogeneous’ versus ‘dense’), although no significant influence of body size. Taxa living in more open habitat types have long‐distance calls with significantly lower mean dominant frequencies than those living in dense habitats. The result obtained in the present analysis is fairly robust against random removal of single or few taxa from the data, and also against the use of different branch‐length transformation models in phylogenetic regression. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 487–500.     

COMPARATIVE METHODS FOR THE ANALYSIS OF CONTINUOUS VARIABLES: GEOMETRIC INTERPRETATIONS

Abstract This study is concerned with statistical methods used for the analysis of comparative data (in which observations are not expected to be independent because they are sampled across phylogenetically related species). The phylogenetically independent contrasts (PIC), phylogenetic generalized least‐squares (PGLS), and phylogenetic autocorrelation (PA) methods are compared. Although the independent contrasts are not orthogonal, they are independent if the data conform to the Brownian motion model of evolution on which they are based. It is shown that uncentered correlations and regressions through the origin using the PIC method are identical to those obtained using PGLS with an intercept included in the model. The PIC method is a special case of PGLS. Corrected standard errors are given for estimates of the ancestral states based on the PGLS approach. The treatment of trees with hard polytomies is discussed and is shown to be an algorithmic rather than a statistical problem. Some of the relationships among the methods are shown graphically using the multivariate space in which variables are represented as vectors with respect to OTUs used as coordinate axes. The maximum‐likelihood estimate of the autoregressive parameter, ρ, has not been computed correctly in previous studies (an appendix with MATLAB code provides a corrected algorithm). The importance of the eigenvalues and eigenvectors of the connection matrix, W, for the distribution of ρ is discussed. The PA method is shown to have several problems that limit its usefulness in comparative studies. Although the PA method is a generalized least‐squares procedure, it cannot be made equivalent to the PGLS method using a phylogenetic model.     

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.     

Patterns of sexual size dimorphism in Chelonia

Macroevolutionary patterns of sexual size dimorphism (SSD) indicate how sexual selection, natural selection, and genetic and developmental constraints mold sex differences in body size. One putative pattern, known as Rensch's rule, posits that, among species with female‐larger SSD, the relative degree of SSD declines with species' body size, whereas, among male‐larger SSD species, relative SSD increases with size. Using a dataset of 196 chelonian species from all fourteen families, we investigated the correlation in body size evolution between male and female Chelonia and the validity of Rensch's rule for the taxon and within its major clades. We conclude that male–female correlations in body size evolution are high, although these correlations differ among chelonian families. Overall, SSD scales isometrically with body size; Rensch's rule is valid for only one family, Testudinidae (tortoises). Because macroevolutionary patterns of SSD can vary markedly among clades, even in a taxon as morphologically conservative as Testudines, one must guard against inappropriately pooling clades in comparative studies of SSD. The results of the present study also indicate that regression models that assume the x‐variable (e.g. male body size) is measured without statistical error, although frequently reported, will result in erroneous conclusions about phylogenetic trends in sexual size dimorphism. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 396–413.     

Ecological and evolutionary components of body size: geographic variation of venomous snakes at the global scale

Biogeographical patterns of animal body size and the environmental and evolutionary mechanisms that may be driving them have been broadly investigated in macroecology, although just barely in ectotherms. We separately studied two snake clades, Viperidae and Elapidae, and used phylogenetic eigenvector regression and ordinary least squares multiple regression methods to perform a global grid-based analysis of the extent at which the patterns of body size (measured for each species as its log₁₀-transformed maximum body length) of these groups are phylogenetically structured or driven by current environment trends. Phylogenetic relatedness explained 20% of the across-species size variation in Viperidae, and 59% of that of Elapidae, which is a more recent clade. Conversely, when we analysed spatial trends in mean body size values (calculated for each grid-cell as the average size of its extant species), an environmental model including temperature, precipitation, primary productivity (as indicated by the global vegetation index) and topography (range in elevation) explained 37.6% of the variation of Viperidae, but only 4.5% of that of Elapidae. These contrasted responses of body size patterns to current environment gradients are discussed, taking into consideration the dissimilar evolutionary histories of these closely-related groups. Additionally, the results obtained emphasize the importance of the need to start adopting deconstructive approaches in macroecology.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 94–109.     

Post-Eocene climate change, niche conservatism, and the latitudinal diversity gradient of New World birds

Aim The aim of this study was to test a variant of the evolutionary time hypothesis for the bird latitudinal diversity gradient derived from the effects of niche conservatism in the face of global climate change over evolutionary time. Location The Western Hemisphere. Methods We used digitized range maps of breeding birds to estimate the species richness at two grain sizes, 756 and 12,100 km². We then used molecular phylogenies resolved to family to quantify the root distance (RD) of each species as a measure of its level of evolutionary development. Birds were classified as ‘basal’ or ‘derived’ based on the RD of their family, and richness patterns were contrasted for the most basal and most derived 30% of species. We also generated temperature estimates for the Palaeogene across the Western Hemisphere to examine how spatial covariation between past and present climates might make it difficult to distinguish between ecological and evolutionary hypotheses for the current richness gradient. Results The warm, wet tropics support many species from basal bird clades, whereas the northern temperate zone and cool or dry tropics are dominated by species from more recent, evolutionarily derived clades. Furthermore, crucial to evaluating how niche conservatism among birds may drive the hemispherical richness gradient, the spatial structure of the richness gradient for basal groups is statistically indistinguishable from the overall gradient, whereas the richness gradient for derived groups is much shallower than the overall gradient. Finally, modern temperatures and the pattern of climate cooling since the Eocene are indistinguishable as predictors of bird species richness. Main conclusions Differences in the richness gradients of basal vs. derived clades suggest that the hemispherical gradient has been strongly influenced by the differential extirpation of species in older, warm‐adapted clades from parts of the world that have become cooler in the present. We propose that niche conservatism and global‐scale climate change over evolutionary time provide a parsimonious explanation for the contemporary bird latitudinal diversity gradient in the New World, although dispersal limitation of some highly derived clades probably plays a secondary role.     

Phylogenetic structure and phylogenetic diversity of angiosperm assemblages in forests along an elevational gradient in Changbaishan,China

Aims Understanding what drives the variation in species composition and diversity among local communities can provide insights into the mechanisms of community assembly. Because ecological traits are often thought to be phylogenetically conserved, there should be patterns in phylogenetic structure and phylogenetic diversity in local communities along ecological gradients. We investigate potential patterns in angiosperm assemblages along an elevational gradient with a steep ecological gradient in Changbaishan, China.Methods We used 13 angiosperm assemblages in forest plots (32×32 m) distributed along an elevational gradient from 720 to 1900 m above sea level. We used Faith's phylogenetic diversity metric to quantify the phylogenetic alpha diversity of each forest plot, used the net relatedness index to quantify the degree of phylogenetic relatedness among angiosperm species within each forest plot and used a phylogenetic dissimilarity index to quantify phylogenetic beta diversity among forest plots. We related the measures of phylogenetic structure and phylogenetic diversity to environmental (climatic and edaphic) factors.Important findings Our study showed that angiosperm assemblages tended to be more phylogenetically clustered at higher elevations in Changbaishan. This finding is consistent with the prediction of the phylogenetic niche conservatism hypothesis, which highlights the role of niche constraints in governing the phylogenetic structure of assemblages. Our study also showed that woody assemblages differ from herbaceous assemblages in several major aspects. First, phylogenetic clustering dominated in woody assemblages, whereas phylogenetic overdispersion dominated in herbaceous assemblages; second, patterns in phylogenetic relatedness along the elevational and temperature gradients of Changbaishan were stronger for woody assemblages than for herbaceous assemblages; third, environmental variables explained much more variations in phylogenetic relatedness, phylogenetic alpha diversity and phylogenetic beta diversity for woody assemblages than for herbaceous assemblages.     

Host abundance,durability, basidiome form and phylogenetic isolation determine fungivore species richness

Species with close associations to a specific host species, such as parasites and phytophages, make immense contributions to biodiversity. Hence, factors determining the variation in species richness among hosts are a main focus of ecological research. Investigations of determining factors of fungivorous species among host species are still scarce. Based on ecological patterns of parasites and phytophages, we hypothesized that the species richness of tree‐fungus beetles of the family Ciidae (Coleoptera) would increase with increasing basidiome size, niche diversity of the growth form, durability, increasing abundance and decreasing phylogenetic isolation of the host fungus. Our generalized least‐squares model, controlled by host phylogeny, revealed that Ciidae species richness increases with host abundance, but decreases with host phylogenetic isolation. In contrast with our prediction, Ciidae species richness was higher in annual basidiomes than in perennials. Pileate basidiomes revealed higher species richness than resupinate and stipitate basidiomes, which may be interpreted as being a result of their higher host niche diversity. The importance of host abundance, measured on the landscape scale, corroborates that fungivore species richness among macrofungal hosts is determined by factors similar to those that determine parasite and phytophage species richness among their hosts. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 699–708.     

Global pattern of phylogenetic species composition of shark and its conservation priority

The diversity of marine communities is in striking contrast with the diversity of terrestrial communities. In all oceans, species richness is low in tropical areas and high at latitudes between 20 and 40°. While species richness is a primary metric used in conservation and management strategies, it is important to take into account the complex phylogenetic patterns of species compositions within communities. We measured the phylogenetic skew and diversity of shark communities throughout the world. We found that shark communities in tropical seas were highly phylogenetically skewed, whereas temperate sea communities had phylogenetically diversified species compositions. Interestingly, although geographically distant from one another, tropical sea communities were all highly skewed toward requiem sharks (Carcharhinidae), hammerhead sharks (Sphyrnidae), and whale sharks (Rhincodon typus). Worldwide, the greatest phylogenetic evenness in terms of clades was found in the North Sea and coastal regions of countries in temperate zones, such as the United Kingdom, Ireland, southern Australia, and Chile. This study is the first to examine patterns of phylogenetic diversity of shark communities on a global scale. Our findings suggest that when establishing conservation activities, it is important to take full account of phylogenetic patterns of species composition and not solely use species richness as a target. Protecting areas of high phylogenetic diversity in sharks, which were identified in this study, could form a broader strategy for protecting other threatened marine species.     

Macroecological explanations for differences in species richness gradients: a canonical analysis of South American birds

Aim To evaluate how spatial variation of species richness in different bird orders responds to environmental gradients and determine which order level trait best predicts these relationships. Location South America. Methods A canonical correlation analysis was performed between the species richness in each of 17 bird orders and eight environmental variables in 374, 220 × 220 km cells. Loadings associated with the first two canonical variables were regressed against six order‐level predictors, including diversification level (number of species in each order), body size, median geographical range size and characteristics included in the model to control Type I error rates (the phylogenetic relationship among orders and levels of local‐scale spatial autocorrelation). Results Richness patterns of 14 bird orders were highly correlated with the first canonical axis, indicating that most orders respond similarly to energy‐water gradients (primarily actual evapotranspiration, minimum temperature and potential evapotranspiration). In contrast, species richness within Trochiliformes, Apodiformes and Galliformes were also correlated with the second canonical variable, representing measures of mesoscale climatic variation (range in elevation within cells, minimum temperature, and the interaction term between them) and landcover (habitat diversity). We also found that total diversification within orders was the best predictor of the loadings associated with the first canonical axis, whereas body size of each order best predicted loadings on the second axis. Conclusion Our results broadly support climatic‐related hypotheses as explanations for spatial variation in species richness of different orders. However, both historical (order‐specific variation in speciation rates) and ecological (dispersal of species that evolved by independent processes into areas amenable to birds) processes can explain the relationship between order level traits, such as body size and diversification level, and magnitude of response to current environment, furnishing then guidelines for a further and deeper understanding of broad‐scale diversity gradients.