title: Host shifts enhance diversification of ectomycorrhizal fungi: diversification rate analysis of the ectomycorrhizal fungal genera Strobilomyces and Afroboletus with an 80-gene phylogeny.
abstract: Mutualisms with new host lineages can provide symbionts with novel ecological opportunities to expand their geographical distribution, thereby leading to evolutionary diversification. Because ectomycorrhizal (ECM) fungi provide ideal opportunities to test the relationship between host shifts and diversification, we tested whether mutualism with new host lineages could increase the diversification rates of ECM fungi. Using a Bayesian tree inferred from 23 027-base nucleotide sequences of 80 single-copy genes, we tested whether the diversification rate had changed through host-shift events in the monophyletic clade containing the ECM fungal genera Strobilomyces and Afroboletus. The results indicated that these fungi were initially associated with Caesalpinioideae/Monotoideae in Africa, acquired associations with Dipterocarpoideae in tropical Asia, and then switched to Fagaceae/Pinaceae and Nothofagaceae/Eucalyptus. Fungal lineages associated with Fagaceae/Pinaceae were inferred to have approximately four-fold and two-fold greater diversification rates than those associated with Caesalpinioideae/Monotoideae and Dipterocarpoideae or Nothofagaceae/Eucalyptus, respectively. Moreover, the diversification rate shift was inferred to follow the host shift to Fagaceae/Pinaceae. Our study suggests that host-shift events, particularly those occurring with respect to Fagaceae/Pinaceae, can provide ecological opportunities for the rapid diversification of Strobilomyces-Afroboletus. Although further studies are needed for generalization, we propose a possible diversification scenario of ECM fungi.
authors.affiliation: Center for Ecological Research, Kyoto University, 509-3, 2-chome, Hirano, Otsu, Shiga, 520-2113, Japan.|Department of Environmental Solution Technology, Facility of Science & Technology, Ryukoku University, Seta-Oe, Otsu, 520-2194, Shiga, Japan.
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Sato
authors.affiliation: National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 2-12-4, Fuku-ura, Kanazawa-ku, Yokohama, Kanagawa, 236-8648, Japan.
authors.forename: Akifumi S
authors.initials: AS
authors.lastname: Tanabe
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyoku Kyoto, 606-8501, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Toju
mesh_terms: D001487:Basidiomycota / Q000145:classification* / Q000235:genetics* / Q000502:physiology; D001499:Bayes Theorem; D044822:Biodiversity; D005800:Genes, Fungal; D049810:Genetic Speciation; D038821:Mycorrhizae / Q000502:physiology*; D010802:Phylogeny
keywords: Illumina MiSeq; biogeography; coevolution; mutualism; radiation; speciation; species interaction