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.