Local community assembly processes shape β-diversity of soil phoD-harbouring communities in the Northern Hemisphere steppes

Aim: The contemporary coexistence theory suggests that species pool, environmental filtering, dispersal assembly processes, ecological drift and biotic interactions collectively determine the beta-diversity of communities. However, we know little about the biogeographical patterns of the beta-diversity of microbial communities harbouring the alkaline phosphatase phoD gene (phoD communities, hereafter) and whether these mechanisms are all-important in shaping phoD communities' beta-diversity in natural steppe ecosystems. Location: Northern Hemisphere steppes. Time period: July to August 2018. Major taxa studied: Alkaline phosphatase (phoD gene) encoding community. Methods: Using the high throughput amplicon sequencing method, soil phoD communities were comparatively studied along three representative regions of the Northern Hemisphere steppes, namely the Qinghai-Tibetan Plateau, Inner Mongolian Plateau and the Loess Plateau. Each region harbours three types of steppes (habitats): meadow, typical and desert steppes. Results: We observed significantly higher phoD beta-diversity in the Qinghai-Tibetan than in the Loess and Inner Mongolian Plateaus and significantly lower beta-diversity in the typical steppes than in other steppe types. The decay rates of phoD beta-diversity with geographical distance varied in different steppe regions and types. The phoD beta-diversity was not significantly influenced by species pool; instead, environmental filtering, dispersal assembly processes, ecological drift and biotic interactions jointly shaped the beta-diversity patterns. The beta-deviation variations (beta-diversity excluding the effects of species pool) were influenced by spatial and environmental factors and biotic interactions, among which soil pH was the key environmental determinant. The soil pH driving beta-diversity mechanism was steppe region and habitat specific. Main conclusions: The biogeographical patterns of phoD beta-diversity were mainly driven by local community assembly processes in the Northern Hemisphere steppes.