Phylogenetic estimation reveals the speciation rates of soil nematodes are increased by agricultural managements

Anthropogenic activities, such as agricultural land management, are supposed to negatively affect global biodiversity and influence the development of diverse groups in the tree of life. Yet how agricultural management shape the diversity of microscopic organisms and their evolution in the soil, especially at large spatial scales, remains unknown. Here, we investigated how land-use affecting the biodiversity and underlying evolutionary events of soil nematodes by comparing their communities in paired natural and agricultural soils covering a latitudinal transect spanning 2,500 km across China. In natural habitats, nematode phylogenetic and taxonomic diversity and their species richness showed a hump-shaped relationship with latitudes and peaked at 30° N, while in agricultural habitats those community matrices did not change across the studied latitudinal spectrum. Meanwhile, agricultural management reduced both diversity and richness of nematodes with the effect being more pronounced in subtropical zones. However, evolutionary diversification rates were higher in agricultural than in natural habitats across the entire latitudinal range likely through management-induced reductions of soil organic carbon and shifts of nematode community compositions towards rapidly evolving taxa (r–strategists) in agricultural habitats. Together, our results suggest that the relatively unfavorable environment status induced by agricultural management could accelerate nematode speciation rates even at a cost of losing diversity. These findings increase our understanding of the comprehensive effects of agricultural management on soil biodiversity that might help establish conservation and restoration efforts of soil biodiversity for the purpose of sustainable agriculture.