Meeting Abstract
Tolerance to environmental perturbation may differ among demographic groups within populations, and thus understanding the impact of global warming requires analyses of variation in physiological performance among individuals. Studies on marine invertebrates suggest that large individuals have lower thermal tolerances than small individuals of the same species. We tested for size-specific differences in thermal tolerance using the intertidal porcelain crab, Petrolisthes cinctipes, as a model. Based on work in other systems, we predicted that smaller crabs (carapace length 11-14 mm) would have higher thermal tolerance than larger crabs (carapace length ≥18 mm). To test our prediction, we measured the heart rates of crabs during a temperature ramp mimicking field conditions during a hot low-tide period. We used heart rate break point temperature (BPT) as our metric of thermal tolerance, defined as the temperature at which heart rates begin to decrease as temperatures rise. Contrary to our prediction, no statistically significant difference between small (mean BPT = 28.1 ± 1.6°C) and large (mean BPT = 27.0 ± 0.9°C) P. cinctipes was observed. Additionally, population demographics, such as gender, may be affected differently by the same abiotic climate changes. As P. cinctipes appear to have similar BPTs regardless of size, population-wide changes with larger ecological effects may occur with warming climates.
