Ammon Corl1,2, Alison R. Davis3, Shawn R. Kuchta4, and Barry Sinervo
-Author Affiliations
Department of Ecology and Evolutionary Biology, EMS A316, University of California, Santa Cruz, CA 95064
↵2Present address: Department of Evolutionary Biology, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden.
↵3Present address: Museum of Vertebrate Zoology, University of California, Berkeley, 3101 Valley Life Sciences Building, Berkeley, CA 94720.
↵4Present address: Dartmouth College, Department of Biological Sciences, Gilman Hall, Hanover, NH 03755.
Edited by David B. Wake, University of California, Berkeley, CA, and approved January 11, 2010 (received for review August 21, 2009)
Abstract
Polymorphism may play an important role in speciation because new species could originate from the distinctive morphs observed in polymorphic populations. However, much remains to be understood about the process by which morphs found new species. To detail the steps of this mode of speciation, we studied the geographic variation and evolutionary history of a throat color polymorphism that distinguishes the “rock-paper-scissors” mating strategies of the side-blotched lizard, Uta stansburiana. We found that the polymorphism is geographically widespread and has been maintained for millions of years. However, there are many populations with reduced numbers of throat color morphs. Phylogenetic reconstruction showed that the polymorphism is ancestral, but it has been independently lost eight times, often giving rise to morphologically distinct subspecies/species. Changes to the polymorphism likely involved selection because the allele for one particular male strategy, the “sneaker” morph, has been lost in all cases. Polymorphism loss was associated with accelerated evolution of male size, female size, and sexual dimorphism, which suggests that polymorphism loss can promote rapid divergence among populations and aid species formation.
lizard morph phylogeny rock-paper-scissors Uta stansburiana
Footnotes
1To whom correspondence should be addressed. E-mail:corl@biology.ucsc.edu.
Author contributions: A.C. and B.S. designed research; A.C., A.R.D., S.R.K., and B.S. performed research; A.C. analyzed data; and A.C. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0909480107/DCSupplemental.
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