Recurrent evolution of herbivory in small, cold-climate lizards: Breaking the ecophysiological rules of reptilian herbivory
- †Department of Biology, California State University, Northridge, CA 91330-8303; §Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794-5245; and ¶Ecology, Evolution, and Conservation Biology and Biological Resources Research Center, MS 314, University of Nevada, Reno, NV 89557
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Edited by David B. Wake, University of California, Berkeley, CA, and approved October 2, 2004 (received for review February 23, 2004)
Abstract
Herbivory has evolved in many groups of vertebrates, but it is rare among both extinct and extant nonavian reptiles. Among squamate reptiles, (lizards, snakes, and their relatives), <2% of the >7,800 species are considered to be herbivorous, and herbivory is restricted to lizards. Here, we show that within a group of South American lizards (Liolaemidae, ≈170 species), herbivory has evolved more frequently than in all other squamates combined and at a rate estimated to be >65 times faster. Furthermore, in contrast to other herbivorous lizards and to existing theory, most herbivorous liolaemids are small bodied and live in cool climates. Herbivory is generally thought to evolve only in reptile species that are large bodied, live in warm climates, and maintain high body temperatures. These three well known “rules” of herbivory are considered to form the bases of physiological constraints that explain the paucity of herbivorous reptile species. We suggest that the recurrent and paradoxical evolution of herbivory in liolaemids is explained by a combination of environmental conditions (promoting independent origins of herbivory in isolated cool-climate regions), ecophysiological constraints (requiring small body size in cool climates, yet high body temperatures for herbivores), and phylogenetic history. More generally, our study demonstrates how integrating information from ecophysiology and phylogeny can help to explain macroevolutionary trends.
Footnotes
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↵ ‡ To whom correspondence should be addressed. E-mail: robert.e.espinoza{at}csun.edu.
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Author contributions: R.E.E., J.J.W., and C.R.T. designed research; R.E.E. and J.J.W. performed research; R.E.E. and J.J.W. analyzed data; and R.E.E., J.J.W., and C.R.T. wrote the paper.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: ND2, NADH dehydrogenase subunit II; SVL, snout–vent length.
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Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AY661892–AY661908 and AY662050–AY662079).
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See Commentary on page 16713.
- Copyright © 2004, The National Academy of Sciences
