Meeting Abstract

24.3  Friday, Jan. 4  Thermal stress and the fitness consequences of climate change for ectotherms KINGSOLVER, J.G.*; DIAMOND, S.E.; Univ of North Carolina, Chapel Hill; North Carolina State Univ jgking@bio.unc.edu

Recent models of the ecological effects of global warming on insects and other ectotherms predict that mean fitness will decrease in tropical species but increase in temperate species. This occurs because temperate species have larger ‘thermal safety margins’ (the difference between optimal temperature and mean environmental temperature) than tropical species. These models do not account for mortality due to extreme high temperatures in fluctuating environments: such intermittent heat stresses could reduce the mean fitness of a population to zero. Here, we develop a series of models and an alternative definition of the safety margin that incorporate the effects of heat stress. We parameterize these models for insect species at multiple sites along a latitudinal gradient of environmental temperature. At both tropical and many temperate sites, climate change is predicted to increase the frequency with which species experience extreme summer temperatures above their upper thermal limits. Our simulations suggest that because of increasing heat stress, the negative fitness consequences of climate change may not be limited to tropical ectotherms. The consequences of heat stress will be magnified if climate change increases both mean and seasonal variability in environmental temperatures, especially at higher latitudes.