Meeting Abstract
Temperature has nonlinear effects on most biological rates, so that fluctuating temperatures can alter the mean rates of performance in ectotherms. However, the temporal order and duration of exposure to temperatures (time-dependence) can also have important consequences for thermal sensitivity and performance of ectotherms. For example in Manduca sexta, temperatures that maximize larval growth rates over hourly to daily time scales can be suboptimal or lethal over longer time scales. We quantified how different mean temperatures and diurnal fluctuations in temperature during development can determine mean growth rates and heat tolerance in Manduca larvae. The effects of diurnal temperature fluctuations on mean growth rate depended strongly on mean temperatures. Diurnal fluctuations generally decreased mean growth rates. Our analyses suggest that both nonlinear and time-dependent effects of rearing temperature influenced mean growth rate, especially at higher temperatures. We also tested whether rearing conditions affect larval survival in response to a brief (2h) heat shock at 46-48C (heat-hardening). Initial studies indicate that diurnal fluctuations increased heat-hardening (greater survival after heat shock) even at moderate rearing temperatures. This suggests that fluctuations in temperature, rather than temperature itself, may be more important for eliciting heat-hardening responses.
