Phylogenetic dependence of plant‐soil feedback promotes rare species in a subtropical forest

Negative plant–soil feedback (PSF) has been widely considered to be a primary mechanism maintaining plant diversity. Previous studies have shown that rare species suffer stronger negative conspecific PSF than common species, but it remains unclear how rare species persist if they are more strongly self-limited. Here, we used shade-house and field experiments to test soil feedback effects of phylogenetically related species on seedling growth, with seven species of contrasting local abundance, in a subtropical forest, China. We quantified the PSF of conspecifics and heterospecifics and assessed the phylogenetic dependence of the feedback. Both experiments showed that although rare species suffered strong negative PSF in soils of conspecifics or phylogenetically close heterospecifics, no such feedback was found in the soils of phylogenetically distant heterospecifics. In contrast, common species had no or weak negative conspecific PSF but strong heterospecific soil PSF. Synthesis. The variation in the phylogenetically dependent PSF among rare and common species evidenced in this study ensures that rare species would grow well in the neighbourhood of phylogenetically distant heterospecifics but do poorly under their own or close relatives, while common species perform relatively well in their own neighbourhood but poorly in other's neighbourhood. This phylogenetically dependent PSF facilitates the rare–common species coexistence in communities.