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Edited by David B. Wake, University of California, Berkeley, CA, and approved November 26, 2014 (received for review October 1, 2014)
Significance
The gecko adhesive system has garnered considerable interest from scientists over the past several decades. Most research has focused on the function and microanatomy of the adhesive system. However, it is currently unclear what impact the secondary loss or simplification of the adhesive system might have on the evolutionary biomechanics of gecko locomotion, which is critical for pinpointing the constraints that accompany such an innovation, and ultimately the release from these constraints. We found that geckos exhibit elevated rates of morphological and kinematic evolution when their adhesive system is lost/simplified, providing evidence that the loss of an innovation can have profound evolutionary impacts on organismal structural and functional divergence
Abstract
Innovations permit the diversification of lineages, but they may also impose functional constraints on behaviors such as locomotion. Thus, it is not surprising that secondary simplification of novel locomotory traits has occurred several times among vertebrates and could potentially lead to exceptional divergence when constraints are relaxed. For example, the gecko adhesive system is a remarkable innovation that permits locomotion on surfaces unavailable to other animals, but has been lost or simplified in species that have reverted to a terrestrial lifestyle. We examined the functional and morphological consequences of this adaptive simplification in the Pachydactylus radiation of geckos, which exhibits multiple unambiguous losses or bouts of simplification of the adhesive system. We found that the rates of morphological and 3D locomotor kinematic evolution are elevated in those species that have simplified or lost adhesive capabilities. This finding suggests that the constraints associated with adhesion have been circumvented, permitting these species to either run faster or burrow. The association between a terrestrial lifestyle and the loss/reduction of adhesion suggests a direct link between morphology, biomechanics, and ecology.
Footnotes
- ↵1To whom correspondence should be addressed. Email: thigham{at}ucr.edu.
Author contributions: T.E.H. and A.P.R. designed research; T.E.H., A.V.B.-J., C.E.C., and A.P.R. performed research; T.E.H., A.V.B.-J., C.E.C., and C.D.H. analyzed data; T.E.H. wrote the paper; and C.D.H. contributed to writing.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1418979112/-/DCSupplemental.
Evolutionary biomechanics of gecko locomotion
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