Meeting Abstract
Organisms in sessile life stages rely heavily on physiological plasticity to buffer the effects of thermal stressors. However, local adaptation may constrain the capacity for acclimation to changing thermal conditions. The widespread lizard Sceloporus undulatus lays eggs in shallow nests where embryos experience daily temperature fluctuations. Recently, we found that nesting behavior varies across latitudes such that S. undulatus embryos from warmer southern latitudes experience cooler thermal regimes than northern embryos. Embryos from northern populations grow and develop more quickly than southern embryos, even when reared under the same temperatures, a pattern which could have been driven by geographic variation in nesting behavior. Adaptation of embryo physiology to variation in nesting conditions along latitudinal clines could constrain the capacity for acclimation to changing thermal conditions. Here, we performed reciprocal transplants of eggs from three populations across a latitudinal gradient to examine variation in plasticity of embryonic cardiac performance in response to nest thermal regimes. For the first six weeks of incubation, we measured embryonic heart rates across temperatures at two-hour intervals between the daily minimum and maximum temperatures in each treatment. We then calculated the Q10 and energy of activation of heart rate during each week to compare the capacity for acclimation to changing nest temperatures across geography. Our results will demonstrate how local adaptation of maternal behavior and embryonic physiology may interact to affect thermal acclimatory capacity. Geographic variation in the physiological plasticity of widespread ectotherms during sessile stages of development has significant implications for the ability to buffer negative effects of climate warming.
