frog_metadata_2021.csv

In addition to gradual warming, the effects of climate change also include rapid temperature changes which will expose animals to extreme temperatures at short time scales. This, coupled with substantial evidence that gut microbiota help facilitate host resilience to gradual temperature increases motivated us to ask, how do ectotherm gut microbiota respond to extreme temperature exposure? Does this response depend on the CTmax of the host?To address these questions, we collected wood frogs egg masses from 15 populations in the USA, from as far south as South Carolina, to as far north as Vermont (a roughly 10° latitudinal gradient) and reared them in Storrs, Connecticut. The latitudinal scope of our study design allowed us to also account for the influence of intraspecific variation in body size and adaptations to local climates on both CTmax and the gut microbiota. 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 populations’ upper and lower survivable thermal limits. Exposure to temperatures at the limits of the survivable thermal window may affect the host gut microbiota through direct effects on bacteria, and indirect effects on host physiology.To understand how brief exposure to a host’s CTmax can impact the gut microbial community at different time scales, we exposed post-metamorphic wood frogs to their upper survivable temperatures and then examined their gut microbiota at two timepoints (24h and 96h) post-exposure. We hypothesized that because exposure to CTmax is a stressor for wood frog hosts it would also be a stressor to and would induce changes to the gut microbiota of wood frogs. Specifically, we predicted that CTmax exposure would reduce the diversity of the gut microbiota, shift the composition of the microbiota away from that of frogs not exposed to CTmax, and increase the variability of community composition. We measured the gut microbiota at two timepoints after CTmax exposure and compared it to control frogs to determine whether perturbations to the gut microbiota were temporary or persistent (lasting at least four days).