Temporal stability and geographical divergence of skin microbiota in a treefrog: insights from microbial communities and volatile secretions

Skin microbiota, which is highly sensitive to environmental heterogeneity, together with skin secretions, plays a critical role in defense and communication in amphibians. However, the temporal and geographical patterns of skin microbiota, as well as the composition of the skin volatile secretions remain largely unexplored in many amphibian species. In the present study, we collected skin bacterial samples from the Hainan frilled tree frog (Kurixalus hainanus) in the Lingshui population across four consecutive months (April–July) to assess temporal dynamics, and additionally sampled frogs from the Jinxiu and Shanglin populations to examine geographical differentiation. Skin volatile secretions were also characterized and compared among the three populations. The results showed that temporal variation in skin microbiota was primarily driven by a small fraction of rare taxa, whereas the overall evenness and dominant components of the core skin microbiota remained relatively stable over time. In contrast, pronounced differentiation in microbiota composition was observed among populations, indicating a strong influence of habitat heterogeneity. We also found that skin secretions were largely similar among the three populations. Decanal and 1-octanol were identified as candidate compounds underlying disturbance odors in K. hainanus, and three terpenoid compounds detected exclusively in individuals from the Shanglin population may be derived from environmental sources or synthesized by the resident skin microbiota. Together, our findings characterize the temporal and spatial variation of skin microbiota in K. hainanus, while simultaneously identifying population-level variation in skin volatile secretions among populations and establishing a framework for future research to address the interplay between these two critical skin components.