Gut Microbiome Composition and Diversity Are Associated with Heat Tolerance Plasticity in a Tropical Lizard

AbstractClimate change is detrimentally affecting species worldwide. Against this backdrop, tropical ectotherms, which have evolved under historically stable conditions, are considered especially vulnerable to changing environmental conditions. Phenotypic plasticity may provide a rapid coping mechanism in response to warming. While plasticity is typically attributed to host mechanisms, vertebrates house diverse gut microbial communities that impact host traits and can change rapidly within the host's lifetime. Thus, it is possible that the microbiome may contribute to the capacity of ectotherms to mount plastic responses to environmental warming. We explored this possibility using the Panamanian slender anole (Anolis apletophallus), a tropical forest-dwelling lizard experiencing population declines induced by climate change. We tested for associations between the composition of the gut microbiome in slender anoles and the capacity for plasticity in their heat tolerance at three time points after exposure to an acute heat stress event. We found that the magnitude of host plasticity at two of three time points was significantly associated with gut microbiome composition before heat stress. Furthermore, up to 94% of the variation in host plasticity was explained by gut microbiome diversity at one time point. Our work suggests a potentially key role for the microbiome in modulating plastic responses to climate change in ectothermic vertebrates, although future manipulative experiments are required to confirm causality.