SICB 2015: Use it or Lose it: A Study of Dewlap Size Plasticity in Green Anoles

Anolis carolinensis dewlapping. Photo by Cowenby available on Wikipedia.

Anolis carolinensis dewlapping. Photo by Cowenby available on Wikipedia.

On Sunday, Simon Lailvaux of the University of New Orleans gave one of the first anole talks of the SICB meeting, on his work examining the mechanisms underlying seasonal fluctuations in dewlap size. Simon began the talk by describing observations from field and lab studies (Irschick et al. 2006) that revealed that during the summer breeding season, when male anoles extend the dewlap frequently during behavioral displays, male dewlaps are much larger than during the winter nonbreeding season when the dewlap is used rarely. Simon and his lab then conducted a dietary-restriction study to test the hypothesis that this seasonal plasticity is due to resource availability, but found that diet was not associated with dewlap size (Lailvaux et al. 2012).  So, the search for the mechanism underlying this change in dewlap size was on.

Along with several colleagues from Trinity University – Jack Leifer (a materials engineer) and anolologists Bonnie Kircher and Michele Johnson (full disclosure – that’s yours truly), Simon and colleagues then conducted a laboratory experiment to determine whether reduced dewlap size related to less use in the nonbreeding season. To conduct the experiment, the researchers prevented dewlap extension in one set of male green anoles by tying dental floss loosely around their throats, and compared the dewlap size and skin elasticity of those lizards to an unrestrained control group that could dewlap at will. They found that dewlap size in the restrained group continually decreased over time, as compared to unrestrained lizards that, again, exhibited larger dewlaps in the breeding season. Together, these results suggest that use of the dewlap is directly related to its size. Then, the researchers measured the elasticity of dewlap and non-dewlap (belly) skin, and found that the dewlap is more elastic than belly skin, and that both types of skin samples were more elastic in the summer breeding season than in the winter. Because skin is a dynamic tissue whose mechanical properties are altered by sex steroid hormones, Simon suggested that dewlap size plasticity may be the result of seasonal endocrine fluctuations, combined with behavioral use of the structure.

These results suggest so many next steps.  Look for the upcoming manuscript describing this work in more detail!

References

Irschick, D.J., Ramos, M., Buckley, C., Elstrott, J., Carlisle, E.,Lailvaux, S.P., Bloch, N., Herrel, A. and Vanhooydonck, B. 2006. Are morphology -> performance relationships invariant across different seasons? A test with the green anole lizard (Anolis carolinensis). Oikos 114: 49-59.

Lailvaux, S.P., Gilbert, R.L. and Edwards, J.R. 2012. A performance-based cost to honest signaling in male green anole lizards (Anolis carolinensis). Proceedings of the Royal Society of London B: Biological Sciences 279: 2841-2848

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