Consistent Community Assembly but Contingent Species Pool Effects Drive Β-Diversity Patterns of Multiple Microbial Groups in Desert Biocrust Systems.

One of the key goals of ecology is to understand how communities are assembled. The species co-existence theory suggests that community beta-diversity is influenced by species pool and community assembly processes, such as environmental filtering, dispersal events, ecological drift and biotic interactions. However, it remains unclear whether there are similar beta-diversity patterns among different soil microbial groups and whether all these mechanisms play significant roles in mediating beta-diversity patterns. By conducting a broad survey across Chinese deserts, we aimed to address these questions by investing biological soil crusts (biocrusts). Through amplicon-sequencing, we acquired beta-diversity data for multiple microbial groups, that is, soil total bacteria, diazotrophs, phoD-harbouring taxa, and fungi. Our results have shown varying distance decay rates of beta-diversity across microbial groups, with soil total bacteria showing a weaker distance-decay relationship than other groups. The impact of the species pool on community beta-diversity varied across microbial groups, with soil total bacteria and diazotrophs being significantly influenced. While the contributions of specific assembly processes to community beta-diversity patterns varied among different microbial groups, significant effects of local community assembly processes on beta-diversity patterns were consistently observed across all groups. Homogenous selection and dispersal limitation emerged as crucial processes for all groups. Precipitation and soil C:P were the key factors mediating beta-diversity for all groups. This study has substantially advanced our understanding of how the communities of multiple microbial groups are structured in desert biocrust systems.