Meeting Abstract
Organisms occurring in different areas are exposed to different environmental pressures often causing variation in some trait or suite of traits. Throughout Arkansas diamondback watersnakes (Nerodia rhombifer) occur in natural areas and at fish farms. These snakes are frequently found in large densities on fish farms because of the high food abundance. Fish farms provide an ideal system for the study of morphological variation because the size of fish available as prey varies from farm to farm. Because snakes are gape-limited predators they can only consume prey items that are small enough to be swallowed whole. Therefore, snakes with large heads should be able to swallow larger prey than snakes with smaller heads. Given enough time it is possible that different populations would diverge in morphological traits in such a way that head size is best suited to the prey that is available to them. However, for this to happen the variation must be heritable. To determine the degree to which head shape is heritable we measured three cranial traits on offspring from more than 100 litters (~30 from each population). We estimated quantitative genetic parameters using a full sib design. All cranial measurements are significantly heritable although some variation exists among cranial elements and among popualtions.
