Thermal acclimation has little effect on tadpole resistance to Batrachochytrium dendrobatidis.

Given that climate change is predicted to alter patterns of temperature variability, it is important to understand how shifting temperatures might influence species interactions, including parasitism. Predicting thermal effects on species interactions is complicated, however, because the temperature-dependence of the interaction depends on the thermal responses of both interacting organisms, which can also be influenced by thermal acclimation, a process by which organisms adjust their physiologies in response to a temperature change. We tested for thermal acclimation effects on Lithobates clamitans tadpole susceptibility to the fungus Batrachochytrium dendrobatidis (Bd) by acclimating tadpoles to 1 of 3 temperatures, moving them to 1 of 5 performance temperatures at which we exposed them to Bd, and measuring Bd loads on tadpoles post-exposure. We predicted that (1) tadpole Bd load would peak at a lower temperature than the temperature for peak Bd growth in culture, and (2) tadpoles acclimated to intermediate temperatures would have overall lower Bd loads across performance temperatures than cold- or warm-acclimated tadpoles, similar to a previously published pattern describing tadpole resistance to trematode metacercariae. Consistent with our first prediction, Bd load on tadpoles decreased with increasing performance temperature. However, we found only weak support for our second prediction, as acclimation temperature had little effect on tadpole Bd load. Our results contribute to a growing body of work investigating thermal responses of hosts and parasites, which will aid in developing methods to predict the temperature-dependence of disease.