Gut microbiomes are resilient to acute heat exposure in juvenile wood frogs

To understand how acute exposure to upper thermal maximum can impact the gut microbial community at different time scales, we exposed pos-metamorphic wood frogs to their upper survivable temperatures and then examined their gut microbial communities at two timepoints after exposure. To assess whether trends in the gut microbiota response to CTmax exposure are specific to absolute values of CTmax or are generalizable across different CTmax temperatures which vary with individual body size and population level adaptations to local climate regimes, we assayed wood frogs from 15 populations sourced from as far south as South Carolina, USA, to as far north as Vermont, USA, a roughly 10 degree latitudinal gradient. Frogs from disparate populations may have different critical thermal tolerances because exposure to extreme high and low temperatures, as well as different amounts of climate variability in the past may select for upper and lower survivable thermal limits. Exposure to temperatures at the limits of the survivable thermal window may affect the host microbiota through both direct effects on bacteria, and indirectly via effects on host physiology. While most studies thus far have examined the effects of gradual increases in temperature, which simulate consistently warmer environments and allow for acclimation, the effects of climate change also include rapid temperature changes which will expose animals to extreme survivable temperatures at short time scales.