Meeting Abstract
Predicting the response of organisms to environmental change requires a mechanistic understanding of physiological performance, including how it varies with ontogeny. We present data on the thermal sensitivity of mass specific resting metabolic rate (RMRm) in five larval instars of a laboratory strain of the invasive gypsy moth (Lymantria dispar). Available data for this relationship are often limited to a particular life stage or age group and are measured over a narrow range of temperatures that does not encompass the temperature at which metabolic rate is maximized (Tmax). As a result, predictive models may simply assume that metabolic rate increases with temperature over the “normal” physiological range and that the slope of the relationship between metabolic rate and temperature is invariant within species. In each instar, we observed that across a wide range of physiologically relevant temperatures (13-38°C), RMRm reached Tmax around 31°C and then decreased as temperature continued to increase. We found similar estimates of Tmax across instars and similar thermal sensitivities (slopes). The exception was the 1st instar, which exhibited higher thermal sensitivities on both sides of Tmax. Overall, the relationship between RMRm and temperature was similar, but not invariant across the larval stage. This type of information can help provide a mechanistic understanding of how organisms respond to their thermal environments, including how invasive species like gypsy moth spread across the landscape.
