Meeting Abstract

63.11  Wednesday, Jan. 6  Latitudinal Variation in Locomotor Performance of the Northern Watersnake, Nerodia sipedon DANIKAS, L.N.*; COBB, V.A.; Middle Tennessee State Univ. lndanikas@gmail.com

Locomotor performance is arguably one of the most important physiological mechanisms for capturing prey and avoiding predation, and, is thereby generally subject to pressures of natural selection. For ectothermic animals, locomotor performance varies considerably with temperature. Locomotor performance typically increases with temperature, reaching an “optimal” or maximal efficiency level before declining as the critical thermal maxima is approached. Across a broad geographic range with considerable climate variation, the thermal physiology of ectothermic species could vary in a predictable pattern, exhibiting adaptations to regional conditions. The northern watersnake (Nerodia sipedon) is one of the most wide ranging snake species in North America, and is exposed to a wide range of environmental conditions, making it a good model species to test latitudinal gradients. We examined the effect of temperature on neonate locomotor performance (maximal crawling and swimming speeds) from two latitudes representing the northern and southern localities for this species. Maximal crawling and swimming speed differed significantly between the two populations, with the southern population exhibiting optimal terrestrial locomotor performance at a temperature 5°C higher than that of the northern population. Aquatic trials exhibit similar curves for both northern and southern populations, however performance differed significantly. Optimal temperatures varied between latitudes only for terrestrial tests, which may suggest differences in habitat use by populations. This pattern of separation between the two populations indicates possible thermal adaptations to regional climatic conditions by ectotherms and could potentially influence selective pressures.