Geographic Variation in Body Size and Sexual Size Dimorphism of North American Ratsnakes (Pantherophis spp. sensu lato)

Because body size affects nearly all facets of an organismâ s life history, ecologists have long been interested in large-scale patterns of body size variation as well as why those large-scale patterns often differ between sexes. We explored body size variation across the range of the sexually dimorphic ratsnake complex, Pantherophis spp. sensu lato, formerly Elaphe obsoleta (Say in James, 1823), in North America. We specifically explored whether variation in body size followed latitudinal patterns or varied with climatic variables. We found that body size did not conform to a climatic or latitudinal gradient but instead, some of the populations with the largest snakes occurred near the core of the geographic range and some with the smallest near the northern, western, and southern periphery of the range. Males averaged 14% larger than females although the degree of sexual size dimorphism varied between populations (range : 2-25%). There was a weak trend for male body size to change in relation to temperature whereas female body size did not. Our results indicate that relationships between climate and an ectothermâ s body size are more complicated than linear latitudinal clines and likely differ for males and females.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author