Exceptional among-lineage variation in diversification rates during the radiation of Australia's most diverse vertebrate clade

The disparity in species richness among groups of organisms is one of the most pervasive features of life on earth. A number of studies have addressed this pattern across higher taxa (e.g. ‘beetles’), but we know much less about the generality and causal basis of the variation in diversity within evolutionary radiations at lower taxonomic scales. Here, we address the causes of variation in species richness among major lineages of Australia's most diverse vertebrate radiation, a clade of at least 232 species of scincid lizards. We use new mitochondrial and nuclear intron DNA sequences to test the extent of diversification rate variation in this group. We present an improved likelihood-based method for estimating per-lineage diversification rates from combined phylogenetic and taxonomic (species richness) data, and use the method in a hypothesis-testing framework to localize diversification rate shifts on phylogenetic trees. We soundly reject homogeneity of diversification rates among members of this radiation, and find evidence for a dramatic rate increase in the common ancestor of the genera Ctenotus and Lerista. Our results suggest that the evolution of traits associated with climate tolerance may have had a role in shaping patterns of diversity in this group

Data from: Species interactions mediate phylogenetic community structure in a hyper-diverse lizard assemblage from arid Australia

Evolutionary history can exert a profound influence on ecological communities, but few generalities have emerged concerning the relationships among phylogeny, community membership, and niche evolution. We compared phylogenetic community structure and niche evolution in three lizard clades (Ctenotus skinks, agamids, diplodactyline geckos) from arid Australia. We surveyed lizard communities at 32 sites in the northwestern Great Victoria Desert and generated complete species-level molecular phylogenies for regional representatives of the three clades. We document a striking pattern of phylogenetic evenness within local communities for all groups: pairwise correlations in species abundance across sites are negatively related to phylogenetic similarity. By modeling site suitability based on species' habitat preferences, we demonstrate that phylogenetic evenness generally persists even after controlling for habitat filtering among species. This phylogenetic evenness is coupled with evolutionary lability of habitat-associated traits, to the extent that closely related species are more divergent in habitat use than distantly related species. In contrast, lizard diets are phylogenetically conserved and pairwise dietary overlap between species is negatively related to phylogenetic distance in two of three clades. Our results suggest that contemporary and historical species interactions have led to similar patterns of community structure across multiple clades in one of the world's most diverse lizard communities

Data from: Species interactions mediate phylogenetic community structure in a hyper-diverse lizard assemblage from arid Australia

Evolutionary history can exert a profound influence on ecological communities, but few generalities have emerged concerning the relationships among phylogeny, community membership, and niche evolution. We compared phylogenetic community structure and niche evolution in three lizard clades (Ctenotus skinks, agamids, diplodactyline geckos) from arid Australia. We surveyed lizard communities at 32 sites in the northwestern Great Victoria Desert and generated complete species-level molecular phylogenies for regional representatives of the three clades. We document a striking pattern of phylogenetic evenness within local communities for all groups: pairwise correlations in species abundance across sites are negatively related to phylogenetic similarity. By modeling site suitability based on species' habitat preferences, we demonstrate that phylogenetic evenness generally persists even after controlling for habitat filtering among species. This phylogenetic evenness is coupled with evolutionary lability of habitat-associated traits, to the extent that closely related species are more divergent in habitat use than distantly related species. In contrast, lizard diets are phylogenetically conserved and pairwise dietary overlap between species is negatively related to phylogenetic distance in two of three clades. Our results suggest that contemporary and historical species interactions have led to similar patterns of community structure across multiple clades in one of the world's most diverse lizard communities

Data from: Species interactions mediate phylogenetic community structure in a hyper-diverse lizard assemblage from arid Australia

Evolutionary history can exert a profound influence on ecological communities, but few generalities have emerged concerning the relationships among phylogeny, community membership, and niche evolution. We compared phylogenetic community structure and niche evolution in three lizard clades (Ctenotus skinks, agamids, diplodactyline geckos) from arid Australia. We surveyed lizard communities at 32 sites in the northwestern Great Victoria Desert and generated complete species-level molecular phylogenies for regional representatives of the three clades. We document a striking pattern of phylogenetic evenness within local communities for all groups: pairwise correlations in species abundance across sites are negatively related to phylogenetic similarity. By modeling site suitability based on species' habitat preferences, we demonstrate that phylogenetic evenness generally persists even after controlling for habitat filtering among species. This phylogenetic evenness is coupled with evolutionary lability of habitat-associated traits, to the extent that closely related species are more divergent in habitat use than distantly related species. In contrast, lizard diets are phylogenetically conserved and pairwise dietary overlap between species is negatively related to phylogenetic distance in two of three clades. Our results suggest that contemporary and historical species interactions have led to similar patterns of community structure across multiple clades in one of the world's most diverse lizard communities

LG_phylogenies

LG_phylogenie

Disease Risk in Temperate Amphibian Populations Is Higher at Closed-Canopy Sites

<div><p>Habitat loss and chytridiomycosis (a disease caused by the chytrid fungus <em>Batrachochytrium dendrobatidis</em> - <em>Bd</em>) are major drivers of amphibian declines worldwide. Habitat loss regulates host-pathogen interactions by altering biotic and abiotic factors directly linked to both host and pathogen fitness. Therefore, studies investigating the links between natural vegetation and chytridiomycosis require integrative approaches to control for the multitude of possible interactions of biological and environmental variables in spatial epidemiology. In this study, we quantified <em>Bd</em> infection dynamics across a gradient of natural vegetation and microclimates, looking for causal associations between vegetation cover, multiple microclimatic variables, and pathogen prevalence and infection intensity. To minimize the effects of host diversity in our analyses, we sampled amphibian populations in the Adirondack Mountains of New York State, a region with relatively high single-host dominance. We sampled permanent ponds for anurans, focusing on populations of the habitat generalist frog <em>Lithobates clamitans</em>, and recorded various biotic and abiotic factors that potentially affect host-pathogen interactions: natural vegetation, canopy density, water temperature, and host population and community attributes. We screened for important explanatory variables of <em>Bd</em> infections and used path analyses to statistically test for the strength of cascading effects linking vegetation cover, microclimate, and <em>Bd</em> parameters. We found that canopy density, natural vegetation, and daily average water temperature were the best predictors of <em>Bd</em>. High canopy density resulted in lower water temperature, which in turn predicted higher <em>Bd</em> prevalence and infection intensity. Our results confirm that microclimatic shifts arising from changes in natural vegetation play an important role in <em>Bd</em> spatial epidemiology, with areas of closed canopy favoring <em>Bd</em>. Given increasing rates of anthropogenic habitat modification and the resulting declines in temperate and tropical frogs, understanding how vegetation cover and disease interact is critical for predicting <em>Bd</em> spread and developing appropriate management tools for wild populations.</p> </div

Conditional autoregressive models (CAR) simultaneously testing the effects of natural vegetation, canopy density, and water temperature on <i>Bd</i> prevalence and infection intensity in amphibian populations from the Adirondack region, New York, USA.

<p>Whole-model tests: prevalence: (F = 7.418, n = 10, r² = 0.481, P = 0.026); infection intensity: (F = 38.376, n = 10, r² = 0.950, P<0.001). Std. coeff. stands for standard coefficient. Final models chosen based on Akaike Information Criterion (AICc).</p

Alternative path models, including both direct and indirect effects of canopy density on <i>Bd</i>.

<p>(A) <i>Bd</i> prevalence; (B) <i>Bd</i> infection intensity. The relative strength of each effect is indicated by line width. Grey lines stand for non-significant effects. Numbers are standardized path coefficients (*P<0.05).</p