Evolutionary variation in the mechanics of fiddler crab claws

BMC Evolutionary Biology

John H Christy¹  Stuart P Anderson²  Matthew N George²  Brook O Swanson² 

[1] Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Balboa, Ancon, Republic of Panama;Department of Biology, Gonzaga University, 502 E Boone Ave, Spokane WA 99258, USA

关键词: Trade-off;    Signal efficiency;    Structural damage;    Cuticle damage;    Closing force;   

Others  :  1086807
DOI  :  10.1186/1471-2148-13-137

 received in 2012-10-05, accepted in 2013-06-04,  发布年份 2013

【 摘 要 】

Background

Fiddler crabs, genus Uca, are classic examples of how intense sexual selection can produce exaggerated male traits. Throughout the genus the enlarged “major” cheliped (claw) of the male fiddler crab is used both as a signal for attracting females and as a weapon for combat with other males. However, the morphology of the major claw is highly variable across the approximately 100 species within the genus. Here we address variation, scaling, and correlated evolution in the mechanics of the major claw by analyzing the morphology and mechanical properties of the claws of 21 species of fiddler crabs from the Pacific, Gulf and Atlantic coasts of the Americas.

Results

We find that the mechanics that produce claw closing forces, the sizes of claws and the mechanical strength of the cuticle of claws are all highly variable across the genus. Most variables scale isometrically with body size across species but claw force production scales allometrically with body size. Using phylogenetically independent contrasts, we find that the force that a claw can potentially produce is positively correlated with the strength of the cuticle on the claw where forces are delivered in a fight. There is also a negative correlation between the force that a claw can potentially produce and the size of the claw corrected for the mass of the claw.

Conclusions

These relationships suggest that there has been correlated evolution between force production and armoring, and that there is a tradeoff between claw mechanics for signaling and claw mechanics for fighting.

【 授权许可】

   
2013 Swanson et al.; licensee BioMed Central Ltd.

【 图 表 】

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