Developmental processes underlying the evolution of a derived foot morphology in salamanders
- Museum of Vertebrate Zoology and Department of Integrative Biology, University of California, Berkeley, CA 94720-3160
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Contributed by David B. Wake, October 26, 2007 (received for review October 3, 2007)
Abstract
Interdigital webbing has evolved repeatedly in tropical salamanders (bolitoglossines). This derived foot morphology is only one of many homoplastic traits in this diverse amphibian clade. Indeed, few if any morphological traits sort lineages within this clade. We investigate the processes underlying the homoplastic evolution of morphological characters in these salamanders by analyzing selective and developmental processes that generate interdigital webbing. We show that a pedomorphic developmental change generates the new foot morphology and that pedomorphosis affects a number of morphological traits, thus creating a developmental correlation among them. This correlation among traits is maintained across most species, thus facilitating the repeated evolution of traits. Although we find evidence that the changes in foot morphology are adaptive in one species, the evolution of webbing in all other species does not carry an adaptive signature. The new foot morphology therefore evolves repeatedly, even in the apparent absence of a direct selective advantage.
Footnotes
- †To whom correspondence may be sent at the present address: Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom. E-mail: mj279{at}cam.ac.uk
- ‡To whom correspondence may be addressed. E-mail: wakelab{at}berkeley.edu
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Author contributions: M.J. and D.B.W. designed research; M.J. performed research; M.J. analyzed data; and M.J. and D.B.W. wrote the paper.
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The authors declare no conflict of interest.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0710216105/DC1.
- © 2007 by The National Academy of Sciences of the USA
