73.10 Sunday, Jan. 6 Geographic variation in the response of timekeeping systems to environmental cues in three populations of garter snakes (Thamnophis sirtalis): Common garden experiments LUTTERSCHMIDT, D.I.*; MASON, R.T.; Oregon State Univ., Corvallis; Georgia State Univ., Atlanta; Oregon State Univ., Corvallis Lutterschmidt@gsu.edu
The ability to track changing environmental cues so that intrinsic processes are synchronized with optimal environmental conditions is crucial to survival. One question that remains largely uninvestigated is how timekeeping mechanisms vary among different environments. Using a common garden experiment, we compared 24-h melatonin and corticosterone rhythms, reproductive behavior, and physiological stress responses among 3 different populations of garter snakes (Thamnophis sirtalis) with very different life history characteristics: red-sided garter snakes (T. sirtalis parietalis) from the Interlake region of Manitoba, Canada, red-spotted garter snakes (T. sirtalis concinnus) from the Willamette Valley of western Oregon, and eastern garter snakes (T. sirtalis sirtalis) from south Florida. Melatonin and corticosterone cycles differed significantly among the three snake populations in almost all of the sampling periods during this experiment. Patterns of courtship behavior as well as corticosterone and androgen responses to capture stress also differed significantly among the three populations. These population differences persisted across a wide range of acclimatization conditions and were themselves plastic. Our data support the hypothesis that endogenous timekeeping systems have evolved in the presence of unique environmental conditions and are not plastic across geographic regions. These studies have important implications for predicting the effects of environmental perturbations (e.g., climate change) on the physiology, behavior, and reproductive fitness of animal populations.