Elevational variation in gut microbial community composition and predicted functional potential across three Himalayan redstart species

Environmental gradients and seasonal migration may influence host-associated microbial communities, yet their contributions to gut microbiome variation in montane birds remain poorly understood. We investigated gut microbial communities across 1,300 to 4,200 m in three Himalayan redstarts (Phoenicurus fuliginosus, P. leucocephalus, and P. frontalis) exhibiting contrasting seasonal movement strategies. Using 16S rRNA gene sequencing of 46 fecal samples, we characterized microbial diversity, community composition, distance decay relationships, co-occurrence networks, and predicted functional potential. Elevation was significantly associated with microbial community composition, explaining approximately 3% of variation, whereas host species showed no significant association after accounting for elevation. P. fuliginosus exhibited significant compositional differences among most sampled elevations, whereas P. leucocephalus showed significant positive distance decay relationships. Alpha diversity showed no consistent elevational trend, while core microbial taxa and co-occurrence networks varied among elevational groups. PICRUSt2 analyses identified 28 predicted KEGG Level 3 pathways differing significantly among elevations, including pathways associated with amino acid, lipid, glycan, carbohydrate, and bile acid metabolism. Together, these findings highlight elevation as a significant correlate of gut microbial community composition and predicted functional potential, with distinct patterns of microbial turnover among closely related Himalayan redstarts.