Bioclimatic zonation and spatial-scale dependence of lacustrine microbial assemblages

Abstract

Bioclimatic zonation is critical for understanding how climate shapes biodiversity and biogeographic patterns. However, existing studies have primarily focused on macroorganisms, leaving microbial communities largely underexplored. This study seeks to address this gap through extensive sampling of bacterial communities from 931 sediment samples across 199 lakes in China. Based on the obtained data, we identified five distinct lacustrine microbial bioclimatic zones, each showing significant differences in multiple facets of bacterial diversity (i.e., alpha, beta, and gamma diversity) and clear bioclimatic zone–dependent microbial biogeographic patterns. Notably, the alpha and beta diversity of the bacterial communities showed opposing patterns across bioclimatic zones. Dominant environmental variables—specifically mean annual temperature, elevation, lake hydrological variables, and sediment pH—exerted contrasting effects on the alpha and beta diversity and played critical roles in shaping microbial community distribution at different spatial scales. At continental scales, predominant geographic and climatic variables dictated the patterns of bioclimatic zonation of lacustrine microbial communities. At regional scales, hydrological variables influenced the dispersal capacity of lake microbes, whereas sediment physicochemical variables were the most important selection factors shaping local microbial communities. Furthermore, our findings indicated that bioclimatic boundaries substantially enhanced the contribution of variable selection on bacterial community assembly and led to marked changes in distance–decay relationships in community dissimilarities. Overall, this study established a continental bioclimatic framework for lacustrine microbial communities, clarifying how environmental variables control microbial distributions across spatial scales, providing new insights into microbial biogeography, and advancing our knowledge about biodiversity under future climate change scenarios.