Meeting Abstract

11.4  Saturday, Jan. 4 11:00  Thermal Performance Curves: Modeling and Detecting Patterns of Individual Variation ADOLPH, SC; Harvey Mudd College adolph@g.hmc.edu

Thermal performance curves depict how physiological performance varies with temperature. The evolution of performance curves depends on the pattern of selection and on the quantitative genetic basis of individual variation. In principle, we should expect to observe trade-offs in the location of thermal performance curves along the temperature axis. However, phenotypic variation among individuals within a population most commonly occurs in absolute performance (curve height), rather than along the temperature axis (curve location). As a result, phenotypic correlations between performances at different temperatures are almost always positive, even at the coldest and hottest temperatures where we might expect to see trade-offs. Here, I present a model that includes both temperature trade-offs and variation in overall performance within a population. The model shows how trade-offs at temperature extremes can be masked by individual variation in overall performance. The model also makes predictions about the pattern of phenotypic correlations that should be observed under different scenarios of individual variation in performance curves. I then evaluated data on individual performance across temperatures from several species of lizards, frogs and insects. In the majority of cases, performance correlations became weaker as temperature difference increased. This indicates that performance is less tightly coupled at temperature extremes than at similar temperatures; this result is consistent with expectations from biochemistry. I will describe the implications of these findings for detecting trade-offs and for the evolution of physiological performance curves.