Environmental temperature alters the digestive performance and gut microbiota of a terrestrial amphibian.

Environmental temperature and gut microbial communities can both have profound impacts on the digestive performance of ectothermic vertebrates. Additionally, the diversity, composition and function of gut microbial communities themselves are influenced by temperature. It is typically assumed that the temperature-dependent nature of ectotherm digestive performance is due to factors such as host physiological changes and adaptation to local climatic conditions. However, it is also possible that temperature-induced alterations to gut microbiota may influence the relationship between temperature and digestion. To explore the connections between these three factors, we compared digestive performance and gut microbial community diversity and composition in red-backed salamanders housed at three experimental temperatures: 10, 15 and 20°C. We also investigated associations between specific bacterial taxa and temperature or salamander digestive performance. We found that salamander digestive performance was greatest at 15°C, while gut microbial diversity was reduced at 20°C. Further, gut microbial community composition differed among the three temperature treatments. The relative abundance of 25 bacterial genera was dependent on temperature, with high temperatures being associated with reductions in the relative abundance of disease-resistant bacteria and increases in pathogenic taxa. The relative abundance of four bacterial genera was correlated with salamander energy assimilation, two of which are known to digest chitin, a main component of the red-backed salamander diet. These findings suggest that gut microbiota may mediate the relationship between temperature and digestion in ectotherms. We discuss how global climate change may impact ectotherms by altering host-microbe interactions.