Climate-induced range expansion of cushion plants promotes functional homogenization of soil nematode communities

Global climate change is causing plants and other organisms to naturally expand their ranges to higher latitudes or altitudes. This expansion is leading to a strong reshuffling of biotic interactions with consequent ecosystem functions in the new ranges. We report here that soil fauna communities respond strongly to the cushion plants in a large-scale latitudinal gradient in the Qinghai-Tibet Plateau. Local taxonomic, functional, and phylogenetic diversity of soil nematodes increased with the presence of cushion plants independently of the latitudinal gradient, but communities became more functionally similar in the presence of cushion plants and with increasing latitude. This functional homogenization was driven by deterministic processes through which the presence of cushion plants favored some functional traits (i.e., nematode trophic groups: herbivores and bacterivores). Our study reveals functional homogenizations of soil fauna communities in response to climate warming-induced plant range expansion. Given that soil nematodes represent the most abundant and functionally diverse animal communities in terrestrial ecosystems, these findings indicate important changes in the functional dimension of biodiversity and in the delivery of ecosystem functions under climate change.