Environmental heterogeneity and dispersal limitation simultaneously determine the spatial scaling of different microbial functional groups.

Uncovering the mechanisms driving patterns of diversity across space and through time is of critical importance in microbial community ecology. Previous studies suggest that microorganisms also follow the same spatial scaling patterns as macro-organisms. However, it remains unclear whether different microbial functional groups differ in spatial scaling and how different ecological processes may contribute to such differences. In this study, two typical spatial scaling patterns, taxa-area (TAR) and distance-decay relationships (DDR), were investigated for the whole prokaryotic community and seven microbial functional groups using marker genes, including amoA (AOA), amoA (AOB), aprA, dsrB, mcrA, nifH and nirS. Different microbial functional groups harbored different spatial scaling patterns. Microbial functional groups had weaker TAR slope coefficients than the whole prokaryotic community. The archaeal ammonia-oxidizing group, however, displayed a stronger DDR pattern than the bacterial ammonia-oxidizing group. For both TAR and DDR, rare subcommunities were mainly responsible for the observed microbial spatial scaling patterns. Significant associations between environmental heterogeneity and spatial scaling metrics were observed for multiple microbial functional groups. Dispersal limitation, which positively correlated with phylogenetic breadth, was also strongly associated with the strength of microbial spatial scaling. The results demonstrated that environmental heterogeneity and dispersal limitation simultaneously contributed to microbial spatial scaling patterns. This study links microbial spatial scaling patterns with ecological processes, providing mechanistic insights into the typical diversity patterns followed by microbes.