Base molecular e funcional de convergência fenotípica em lagartos brancos de White Sands

Molecular and functional basis of phenotypic convergence in white lizards at White Sands

Erica Bree Rosenblum a,1, Holger Römpler b,c, Torsten Schöneberg b, and Hopi E. Hoekstra c

-Author Affiliations

aDepartment of Biological Sciences, University of Idaho, Moscow, ID 83843;

bInstitute of Biochemistry, Medical Faculty, University of Leipzig, Leipzig 04103, Germany; and

cDepartment of Organismic and Evolutionary Biology and the Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138

Edited by David M. Hillis, The University of Texas at Austin, Austin, TX, and approved November 23, 2009 (received for review September 24, 2009)

Abstract

There are many striking examples of phenotypic convergence in nature, in some cases associated with changes in the same genes. But even mutations in the same gene may have different biochemical properties and thus different evolutionary consequences. Here we dissect the molecular mechanism of convergent evolution in three lizard species with blanched coloration on the gypsum dunes of White Sands, New Mexico. These White Sands forms have rapidly evolved cryptic coloration in the last few thousand years, presumably to avoid predation. We use cell-based assays to demonstrate that independent mutations in the same gene underlie the convergent blanched phenotypes in two of the three species. Although the same gene contributes to light phenotypes in these White Sands populations, the specific molecular mechanisms leading to reduced melanin production are different. In one case, mutations affect receptor signaling and in the other, the ability of the receptor to integrate into the melanocyte membrane. These functional differences have important ramifications at the organismal level. Derived alleles in the two species show opposite dominance patterns, which in turn affect their visibility to selection and the spatial distribution of alleles across habitats. Our results demonstrate that even when the same gene is responsible for phenotypic convergence, differences in molecular mechanism can have dramatic consequences on trait expression and ultimately the adaptive trajectory.

adaptation    genetics    lizard    Mc1r    speciation

Footnotes

1To whom correspondence should be addressed. E-mail:rosenblum@uidaho.edu.

Author contributions: E.B.R. and H.E.H. designed research; E.B.R. and H.R. performed research; E.B.R. and H.R. analyzed data; and E.B.R., H.R., T.S., and H.E.H. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

See Commentary on page 1815.

This article contains supporting information online at www.pnas.org/cgi/content/full/0911042107/DCSupplemental.

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