Habitat use affects morphological diversification in dragon lizards.

D C Collar,J. A. SCHULTE,J A Schulte,J B Losos,B C O'Meara

doi:10.1111/j.1420-9101.2010.01971.x

Abstract

Habitat use may lead to variation in diversity among evolutionary lineages because habitats differ in the variety of ways they allow for species to make a living. Here, we show that structural habitats contribute to differential diversification of limb and body form in dragon lizards (Agamidae). Based on phylogenetic analysis and ancestral state reconstructions for 90 species, we find that multiple lineages have independently adopted each of four habitat use types: rock-dwelling, terrestriality, semi-arboreality and arboreality. Given these reconstructions, we fit models of evolution to species’ morphological trait values and find that rock-dwelling and arboreality limit diversification relative to terrestriality and semi-arboreality. Models preferred by Akaike information criterion infer slower rates of size and shape evolution in lineages inferred to occupy rocks and trees, and model-averaged rate estimates are slowest for these habitat types. These results suggest that ground-dwelling facilitates ecomorphological differentiation and that use of trees or rocks impedes diversification.

Highlights

One of the great questions in evolutionary biology concerns the causes of differences in diversity among clades
We focused on dragon lizards (Agamidae), an ecologically and morphologically diverse radiation of iguanian lizards comprising roughly 400 species distributed throughout the Old World
Bayesian phylogenetic analysis yielded a set of 1000 ultrametric trees that are generally consistent with previous phylogenetic hypotheses involving agamid lizards (Macey et al, 2000; McGuire & Kiew, 2001; Melville et al, 2001; Schulte et al, 2004a; Hugall et al, 2008)

Summary

Introduction

One of the great questions in evolutionary biology concerns the causes of differences in diversity among clades. Ecological factors are often implicated to explain this pattern because the ecological circumstances available to the members of a lineage contribute to the mode of natural selection they experience and shape ecological divergence, morphological adaptation and the evolution of new species. Other habitats may impose stringent functional constraints that lead to strong selection resisting ecological and phenotypic divergence away from an adaptive peak (Butler & King, 2004; Collar et al, 2009). Habitat types may contribute differently to diversification because they vary in the number and type of species interactions they present, such as the presence or absence of predators (McPeek & Brown, 2000). Some habitats may provide opportunities if they are variable across space in the strength of species interactions (McPeek, 1996) or in their functional demands

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