Stochasticity dominates assembly processes of soil nematode metacommunities on three Asian mountains

Nematodes play an important role in ecosystems; however, very little is known about their assembly processes and the factors influencing them. We studied nematode communities in bulk soils from three Asian mountain ecosystems to determine the assembly processes of free-living nematode metacommunities and their driving factors. On each mountain, elevations span a range of climatic conditions with the potential to reveal assembly processes that predominate across multiple biomes. A phylogenetic null modeling framework was used to analyze 18S rRNA gene amplicons to quantify various assembly processes. We found that phylogenetic turnover between nematode communities on all mountains was dominated by stochastic processes, with "undominated processes" being the most predominant stochastic factor. Elevation has a significant impact on the relative importance of deterministic and stochastic processes. A variety of climatic and edaphic variables significantly influenced the variations in community assembly processes with elevation, even though their impacts were not consistent between the mountains. Overall, our results indicate that free-living nematode metacommunities in a wide range of environments are largely structured by stochastic processes rather than by niche-based deterministic processes, suggesting that metacommunities of soil free-living nematodes may respond to climate change in a largely unpredictable way.