Meeting Abstract
Thermal adaptations and thermoregulatory strategies are used as predictors of physiological performance in ectotherms and may help to understand diversity and distribution patterns. In frogs, aquatic to terrestrial breeding transitions have evolved independently many times, leading to new physiological challenges as they face new, warmer, and more variable thermal environments on land. We hypothesized that species that have evolved terrestrial breeding differ in their thermal parameters (critical thermal maxima and preferred temperature) and thermoregulatory strategies compared to aquatic-breeding species, and higher thermal tolerance may facilitate terrestrial breeding. We studied two sympatric and closely related Neotropical foam-nesting frogs during their reproductive season: Engystomops pustulosus (Ep) that breed in temporary ponds and Leptodactylus fragilis (Lf) that build terrestrial subterranean chambers in areas that will flood. We found that females of Lf preferred higher temperatures in a thermal gradient than females of Ep. Data on environmental temperatures in the reproductive sites of each species will be used to test for a match with their preferred temperatures. Females of Lf also had higher CTMax than either females or males of Ep. Within both species, females tended to have a higher CTMax than males, but in Ep females after oviposition had a significantly lower CTMax than either females with eggs or males. Weight, but not snout-vent length, was correlated with CTMax and females in both species were heavier than males, except for Ep females after oviposition. Altogether, our results suggest that biological aspects such as reproductive status, sex and body condition may affect thermal parameters that are correlated with transitions to terrestrial breeding.
