Cross-Range Comparison of Supraglacial Microbial Communities Between Gongga and Gangrigabu Mountains, Southeast...

The supraglacial environment represents a unique habitat that harbors overlooked biodiversity, which is increasingly threatened by climate warming but remains underexplored. This study aims to investigate bacterial and fungal distribution patterns on five debris-covered glaciers from two typical mountain ranges dominated by a monsoon climate (Mt. Gongga and Mt. Gangrigabu). High-throughput amplicon sequencing of the bacterial 16S rRNA gene (V3-V4 region) and the fungal ITS region was performed using the Illumina MiSeq platform. Despite harsh and nitrogen-limited conditions, the supraglacial debris across two mountain ranges supported phylogenetically diverse microbial taxa. Dominant bacterial families included Sphingomonadaceae, Chitinophagaceae, and Comamonadaceae, while dominant fungal families included Thelephoraceae, Mortierellaceae, and Inocybaceae, highlighting the establishment of specialized microbial assemblages in oligotrophic glacier surface environments. Compared with Mt. Gongga, supraglacial debris from Mt. Gangrigabu exhibited significantly lower bacterial alpha diversity, likely driven by environmental filtering associated with higher pH and total carbon content. In contrast, fungal alpha diversity showed limited regional variation. Notably, we observed a significant "distance decay" pattern in both bacterial and fungal communities, which illustrated a decline in taxonomic similarity with increasing geographic distance across glaciers, particularly pronounced in bacterial communities (R = -0.70, p < 0.001). Microbial community composition exhibited stronger glacier-specific differentiation, heterogeneous environmental selection emerged as the dominant ecological process shaping microbial turnover across isolated glaciers, with pH and carbon content playing dominant roles in shaping microbial community variation. Our cross-range comparison reveals that deterministic environmental filtering among geographically isolated glaciers governs the spatial turnover in supraglacial microbial communities, providing new insights into the ecological mechanisms governing microbial biogeographic patterns in rapidly changing cryospheric ecosystems across the southeastern Tibetan Plateau.