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

Abstract

Nematodes play an important role in ecosystems, yet very little is known about their assembly processes and the factors influencing them. We studied nematode communities in bulk soil from three Asian mountain ecosystems to study 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 the assembly processes predominating 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” as 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 variation of community assembly processes with elevation, even though their impacts were not consistent between the mountains. Overall, our results indicated that free-living nematode metacommunities in a wide range of environments are largely structured by stochastic processes, rather than by niche-based deterministic processes, which suggests that metacommunities of soil free-living nematodes may respond to climate change in a largely unpredictable way.