Host seasonal trophic strategies linked to dietary‐microbiota coupling: A potential mechanism mediating the coexistence of sympatric small rodents

The coexistence mechanisms of sympatric species have long attracted widespread research attention. However, it remains unclear whether sympatric species experiencing the same seasonal conditions exhibit convergent or host-specific gut microbiota responses. We compared the herbivorous Brandt's vole (Lasiopodomys brandtii) and the granivorous Mongolian gerbil (Meriones unguiculatus), two sympatric rodent species with divergent trophic strategies inhabiting the grasslands of Inner Mongolia, China. By integrating plant DNA metabarcoding, gut microbiota profiling and microbial functional output analyses across seasons, we investigated seasonal dietary-microbiome associations. Our results revealed that although seasonal dietary variation affects the composition of the host gut microbiota, the taxonomic and functional plasticity of gut microbiota is strongly influenced by host trophic strategies. Brandt's voles maintained a fermentation-oriented microbiota tightly coupled with seasonal shifts in Poaceae and Cyperaceae intake, exhibiting coordinated changes in microbial taxa, short-chain fatty acid production and cellulase activity. In contrast, Mongolian gerbils exhibited substantial seasonal dietary turnover between Chenopodiaceae and Caragana plants, while maintaining comparatively stable microbial functional outputs, suggesting metabolic buffering. Host trophic strategy, rather than shared environmental seasonality, is related to the strength and functional consequences of the coupling between diet and microbiome. Our results emphasize the gut microbiome as a potential key mechanism underlying trophic niche differentiation and ecological coexistence in wild mammalian communities.