Comparative Analysis of Environmental and Host-Associated Microbiome in Odorrana schmackeri (Auran: Ranidae): Insights into Tissue-Specific Colonization and Microbial Adaptation

Amphibian microbial communities are known to be shaped by host physiology and environmental factors, yet the relative roles of sexual dimorphism and tissue specialization remain poorly understood. Using 16S rRNA gene sequencing, we compared the gastrointestinal and integumentary microbiomes of a monomorphic Chinese frog population, <i>Odorrana schmackeri</i>, inhabiting identical montane streams. Our results showed distinct phylogenetic stratification between niches: Proteobacteria dominated both environmental microbiota and <i>O. schmackeri</i> gut and skin microbiotas but with differential sub-phylum specialization. The soil microbiota was dominated by <i>unclassified_Vicinamibacteraceae</i>, the water microbiota was <i>Limnohabitans</i>-dominated, the skin microbiota was dominated by <i>Bordetella</i>, and the gut microbiota was led by <i>Acinetobacter</i>. Alpha diversity analysis revealed significant tissue- and environmental-based divergences but no sexual differentiation, a pattern confirmed by beta diversity assessments showing stronger microbial community separation by tissue and environmental compartmentalization than by sex. Functional metagenomic prediction indicated convergent enrichment of metabolic pathways across host-associated and environmental communities. These results suggest that microbial community structure in <i>O. schmackeri</i> is principally governed by tissue-specific ecological selection pressures rather than host sexual characteristics. Our findings enhance understanding of microbiome assembly rules in vertebrate ectotherms and identify potential connections between microbiota in different ecological niches.