Genetic and thermal variation influences adaptation to fluctuating temperature in the seed beetle, Callosobruchus maculatus

Abstract

SummaryThe impacts of climate change on biological systems are notoriously difficult to measure, and laboratory studies often do not realistically represent natural fluctuations in environmental conditions. To date, most experimental studies of thermal adaptation test populations at constant temperatures, or they make incremental changes to an otherwise constant mean background state. To address this, we examined the long-term effects of stressful fluctuating daily temperature on several key life history traits in two laboratory populations of the seed beetle, Callosobruchus maculatus. These populations were kept for 19 generations at either a constant control temperature, T=29°C, or at a fluctuating daily cycle with Tmean = 33°C, Tmax=40, and Tmin=26. The latter being a simple representation of daily temperatures in southern central India in May, where this species originally evolved. We found that beetles that had evolved in stressful environments were smaller in body size when switched to a constant 29°C and had far greater reproductive fitness in comparison to beetles from both the constant control and continuously stressful 33°C environments. This suggests that beetles raised in environments with stressful fluctuating temperatures were more phenotypically plastic and had greater genetic variability than control treatment beetles and indicates that populations that experience fluctuations in temperature may be better able to respond to short-term changes in environmental conditions.