Host plant genus‐level diversity is the best predictor of ectomycorrhizal fungal diversity in a Chinese subtropical forest

<jats:title>Abstract</jats:title><jats:p>Microbial diversity is generally far higher than plant diversity, but the relationship between microbial diversity and plant diversity remains enigmatic. To shed light on this problem, we examined the diversity of a key guild of root‐associated microbes, that is, ectomycorrhizal (<jats:styled-content style="fixed-case">EM</jats:styled-content>) fungi along a plant diversity gradient in a Chinese subtropical forest. The results indicated that <jats:styled-content style="fixed-case">EM</jats:styled-content> fungal diversity was positively correlated with host plant diversity. Furthermore, this relationship was best predicted by host genus‐level diversity, rather than species‐level diversity or family‐level diversity. The generality of this finding was extended beyond our study system through the analyses of 100 additional studies of <jats:styled-content style="fixed-case">EM</jats:styled-content> fungal communities from tropical and temperate forests. Here as well, <jats:styled-content style="fixed-case">EM</jats:styled-content> fungal lineage composition was significantly affected by <jats:styled-content style="fixed-case">EM</jats:styled-content> plant diversity levels, and some <jats:styled-content style="fixed-case">EM</jats:styled-content> fungal lineages were co‐associated with some host plant genera. These results suggest a general diversity maintenance mechanism for host‐specific microbes based on higher order host plant phylogenetic diversity.</jats:p>