Meeting Abstract

2.4  Thursday, Jan. 3  Influence of diapause timing on the evolution of thermotolerance in Wyeomyia smithii RAGLAND, GJ*; KINGSOLVER, JG; University of Florida; University of North Carolina gragland@ufl.edu

Tolerance of extreme temperatures is a major adaptation to seasonal environments, often exhibiting intra- and interspecific geographic variation that is correlated with environmental temperatures. Climatic data show that winter minimum temperatures decline more rapidly than summer maxima with increasing latitude, leading to the prediction that there should be greater geographic variation in cold compared to heat tolerance. Geographic trends in phenology may counter this climatic trend, however. For example, the timing of insect diapause (dormancy) often changes with geography such that populations further north actively grow and reproduce during a shorter annual time window compared to southern populations. We show that active stages in the pitcher plant mosquito actually encounter similar exposure to stressful cold temperatures across geography because of evolved differences in diapause timing. Despite this similarity in the thermal environment, adults (which are only present during the growing season) demonstrate greater cold tolerance in the north than in the south, mediated primarily by stronger acclimation responses in the north. We discuss potential mechanisms producing the observed pattern and implications for life history evolution in seasonal environments.