Life Stage and Proximity to Roads Shape the Skin Microbiota of Eastern Newts (Notophthalmus viridescens)

Host-associated microbiomes play an essential role in the health of organisms, including immune system activation, metabolism, and energy uptake. It is well established that microbial communities differ depending on the life stage and natural history of the organism. However, the effects of life stage and natural history on microbial communities may also be influenced by human activities. We investigated the effects of amphibian life stage (terrestrial eft vs. aquatic adult) and proximity to roadways on newt skin bacterial communities. We found that the eft and adult life stages differed in bacterial community composition; however, the effects of roads on community composition was more evident in the terrestrial eft stage compared to the aquatic adult stage. Terrestrial efts sampled close to roads possessed richer communities than those living further away from the influence of roads. When accounting for ASVs with predicted antifungal capabilities, in the adult life stage, we observed a decrease in anti-fungal bacteria with distance to roads. In contrast, in the eft stage, we found an increase in anti-fungal bacteria with distance to roads. Our results highlight the need to consider the effects of human activities when evaluating how host-associated microbiomes differ across life stages of wildlife