Keeping Time in the Dark: The Neuroendocrinology of Seasonal Reproduction in Garter Snakes (pp. 265-290)
Authors: (Deborah I. Lutterschmidt, Portland State University, OR, USA)
Abstract: One of the most critical life history traits subject to environmental control is reproduction. Early in my research career, I became fascinated by a conundrum in biological rhythms research. How do animals that hibernate deep underground for extended periods of time successfully synchronize reproductive physiology and behavior with the environment? If photoperiod information isnít accessible, can changes in ground temperature or humidity provide a sufficient signal for synchronization of an internal clock? Are evolutionary differences in these timekeeping mechanisms at the route of observed variation in the timing of reproductive activity both between sexes and among populations? While these questions are universal to all vertebrates, common garter snakes (Thamnophis sirtalis) are an exceptionally robust model system for understanding the environmental control of reproduction. Thamnophis sirtalis is one of the most abundant reptiles in North America and has an extensive range, from south central Canada southward to the Gulf of Mexico and from east to west coasts. Thus, within a single genus, multiple scales can be used for studying the evolution of reproductive regulatory mechanisms. Like many ectotherms, low temperature exposure during winter dormancy plays a critical role in activating seasonal reproductive behavior in garter snakes. Research in my laboratory is aimed at understanding (1) the neuroendocrine mechanisms that mediate the effects of temperature on seasonal reproduction; and (2) whether variation in the sensitivity of reproductive regulatory mechanisms relates to differences in reproductive timing across environments, populations, and phylogenies. Importantly, these studies may provide valuable insights into understanding the potential impacts of climate change on animal populations, both from a proximate, mechanistic level to an ultimate, evolutionary perspective.