Fang Length Evolution in Vipers is Predicted by Furred and Feathered Diets
Holding, Matthew
Department of Biological Science
Florida State University
Tallahassee, Florida, USA matthewholding28@gmail.com
Trevine, Vivian C.
Instituto Butantan
São Paulo, Brazil
Zinenko, Oleksandr
Museum of Nature
V. N. Karazin Kharkiv National University
Kharkiv, Ukraine
Strickland, Jason L. Rautsaw, Rhett M.
Mason, Andrew J.
Hofmann, Erich P.
Parkinson, Christopher L. Department of Biological Sciences
Clemson University
Clemson, South Carolina, USA
Grazziotin, Felipe G.
Instituto Butantan
São Paulo, Brazil
Summers, Adam P. Department of Biology and School of Aquatic and Fisheries Sciences University of Washington
Friday Harbor, Washington, USA
Santana, Sharlene E. Department of Biology
University of Washington
Seattle, Washington, USA
Davis, Mark A.
Illinois Natural History Survey Champaign, Illinois, USA
Rokyta, Darin R.
Department of Biological Science
Florida State University Tallahassee, Florida, USA
Fangs, stingers, spines, and harpoons are used by diverse animal taxa to inject venom into their prey. Strong selection on venom composition has been repeatedly documented, and we might expect the venom injection apparatus to be under similarly strong selection to meet specific functional demands. Snakes in the family Viperidae (true vipers and pitvipers) consist of ~320 species widely studied by both ecologists and evolutionary biologists. Vipers provide an opportunity to determine how the venom injections systems evolve in response to functional demands of prey killing. Utilizing museum collections, we obtained measurements of fang length in >2000 individual specimens representing 200 viper species. We document the mode and tempo of fang length evolution across this diverse family, and test for relationships between ecology and the rate of fang length evolution across clades. We then leverage data collected from over 100 published diet studies to test the hypothesis that longer fangs evolved in response to demands associated with feeding on prey with coverings of fur or feathers. We find support for this hypothesis, where the percentage of mammals and birds in viper diets is positively correlated with relative fang length. Finally, when controlling for head size, the Gaboon Viper is dethroned as the snake species with the longest fangs, and overtaken instead by the Speckled Forest Pitviper of South America. Venom and the venom delivery system merit further work to determine if they are part of a broader functional and evolutionary module that facilitates feeding in venomous animals.