Meeting Abstract
P3.122 Saturday, Jan. 5 Unifying indices of heat tolerance in ectotherms COOPER, B. S.*; WILLIAMS, B. H.; ANGILLETTA, M. J.; Indiana State Univ, Terre Haute; Indiana State Univ, Terre Haute; Indiana State Univ, Terre Haute brandonscooper@hotmail.com
Survival and reproduction directly depend on an organism�s ability to deal with thermal extremes. Researchers commonly rely on indices of heat tolerance to infer the limits of performance in nature. But many methods are used to estimate heat tolerance, which complicates comparisons among populations and species. Here, we relate several measures of heat tolerance based on the concept of a performance curve. We show that knockdown times or LT50s (median time until death) can be used to predict knockdown temperatures. We illustrate this approach with data for a terrestrial isopod, Porcellio scaber. We measured both knockdown times and knockdown temperatures for isopods from the same population. Knockdown times were measured at 0.5�C intervals between 38� and 42�C. A linear model was fit to the knockdown times and the predicted knockdown temperature was derived by finding the intercept of this model. Using Akaike’s information criterion (AIC), we found substantial support for our linear model when compared to an exponential model (difference in AIC = 1.6). The predicted knockdown temperature (41.7�C) was nearly identical to the actual knockdown temperature (41.8�C). This close match indicates that neither cumulative heat shock nor rapid acclimation occurred during measures of knockdown temperature, as assumed by our model. Our results support the possibility of conceptually unifying several measures of thermal physiology.
