Biology

Directional evolution of stockiness coevolves with ecology and locomotion in lizards

Document Type

Article

Abstract

Although studied in many taxa, directional macroevolution remains difficult to detect and quantify. We present an approach for detecting directional evolution in subclades of species when relatively few species are sampled, and apply it to studying the evolution of stockiness in Phrynosomatine lizards. Our approach is more sensitive to detecting the tempo of directional evolution than other available approaches. We use ancestral reconstruction and phylogenetic mapping of morphology to characterize the direction and magnitude of trait evolution. We demonstrate a directional trend toward stockiness in horned lizards, but not their sister groups, finding that stockier species tend to have relatively short and wide bodies, and relatively short heads, tails, and limbs. Ornstein-Uhlenbeck models show that the directional trend in horned lizards is due to a shift in selective regime and stabilizing selection as opposed to directional selection. Bayesian evolutionary correlation analyses indicate that stockier species run more slowly and eat a larger proportion of ants. Furthermore, species with larger horns tend to be slower and more ant-specialized. Directional evolution toward a stocky body shape has evolved in conjunction with changes in a suite of traits, representing a complex example of directional macroevolution. © 2008 The Author(s).

Publication Title

Evolution

Publication Date

2009

Volume

63

Issue

1

First Page

215

Last Page

227

ISSN

0014-3820

DOI

10.1111/j.1558-5646.2008.00534.x

Keywords

Bayesian methods, defensive structures, diet, macroevolution, Phrynosomatinae, sprint speed

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