Meeting Abstract
Sexual size dimorphism (SSD) can vary in both direction and magnitude among populations and species, but the extent to which this variation is associated with differences in metabolism is not well known. Mechanistically, variation in metabolism can be associated with differential investment of energy into maintenance, activity, reproduction, and growth. To address this, we compared resting metabolic rate (RMR) of male and female brown anole lizards (A. sagrei) from two populations (one from the island of Eleuthera and the other from the island of Great Exuma) with pronounced variation in the magnitude of male-biased SSD. Previous research in this system has shown that, whereas females from each population are similar in growth and body size, males from Great Exuma grow more quickly and attain larger body sizes than males from Eleuthera, and this occurs in the wild, under common garden conditions in the lab, and in lab-raised progeny. Thus, we predicted that any population differences in RMR would be more pronounced for males than females. We used stop-flow respirometry to examine how RMR varies with temperature and time of day for males and females from each population. Consistent with our prediction, we found that RMR of males from Eleuthera was significantly higher than that of males from Great Exuma at 25°C and 30°C, and marginally higher at 35°C. In contrast, RMR of females did not differ between populations at any temperature. This research indicates that the smaller body size of males on Eleuthera can be partially explained by their higher RMR, compared to Great Exuma. More broadly, our work suggests that differential allocation of energy into resting metabolism versus growth can be linked to intraspecific variation in the magnitude of SSD.
