Meeting Abstract
5.1 Sunday, Jan. 4 Body size variation among Arizona populations of the western diamond-backed rattlesnake (Crotalus atrox) is predicted by GIS-based estimates of isothermality and precipitation AMARELLO, MELISSA*; NOWAK, E.M.; TAYLOR, E.N.; SCHUETT, G.W.; REPP, R.A.; ROSEN, P.C.; HARDY, D.L.; Southern Illinois University, Carbondale, IL; United States Geological Survey, Northern Arizona University, Flagstaff, AZ; California Polytechnic State University, San Luis Obispo, CA; Georgia State University, Atlanta, GA; National Optical Astronomy Observatory, Tucson, AZ; University of Arizona, Tucson, AZ; 7585 S. Main Ave, Tucson, AZ m.amarello@gmail.com
In many vertebrates, differences in resource availability and quality are important influences contributing to intraspecific variation in body size, which is coupled with numerous life-history traits. Here, we examined body size variation in relation to resource availability among Arizona populations of the western diamond-backed rattlesnake (Crotalus atrox) using GIS-based environmental data. The broad physiographic structure and variable adult snout-vent length (SVL) of C. atrox in Arizona provide an ideal model situation to investigate proximate determinants of geographic variation in body size. Our hypothesis asserted that more resources permit continued growth after sexual maturity to an eventual larger body size; thus, adult C. atrox will have greater SVL in areas with enhanced or perceived resource abundance. To test this idea, we used precipitation and isothermality to characterize resource availability in a mixed linear model to explain geographic variation in SVL of adult C. atrox. In support of our predictions, individuals were larger at sites that were more isothermic and wetter. Our analysis demonstrates the importance of using GIS-based environmental variables and linear mixed effects models to understand geographic variation in body size in lieu of restricting analysis to only a single variable under the framework of a simpler model.
