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 β-diversity of communities. However, we know little about the biogeographical patterns of the β-diversity of microbial communities harbouring the alkaline phosphatase phoD gene (phoD communities, hereafter) and whether these mechanisms are all-important in shaping phoD communities’ β-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 β-diversity in the Qinghai-Tibetan than in the Loess and Inner Mongolian Plateaus and significantly lower β-diversity in the typical steppes than in other steppe types. The decay rates of phoD β-diversity with geographical distance varied in different steppe regions and types. The phoD β-diversity was not significantly influenced by species pool; instead, environmental filtering, dispersal assembly processes, ecological drift and biotic interactions jointly shaped the β-diversity patterns. The β-deviation variations (β-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 β-diversity mechanism was steppe region and habitat specific. Main conclusions: The biogeographical patterns of phoD β-diversity were mainly driven by local community assembly processes in the Northern Hemisphere steppes.