title: Into and out of the tropics: global diversification patterns in a hyperdiverse clade of ectomycorrhizal fungi.
abstract: Ectomycorrhizal (ECM) fungi, symbiotic mutualists of many dominant tree and shrub species, exhibit a biogeographic pattern counter to the established latitudinal diversity gradient of most macroflora and fauna. However, an evolutionary basis for this pattern has not been explicitly tested in a diverse lineage. In this study, we reconstructed a mega-phylogeny of a cosmopolitan and hyperdiverse genus of ECM fungi, Russula, sampling from annotated collections and utilizing publically available sequences deposited in GenBank. Metadata from molecular operational taxonomic unit cluster sets were examined to infer the distribution and plant association of the genus. This allowed us to test for differences in patterns of diversification between tropical and extratropical taxa, as well as how their associations with different plant lineages may be a driver of diversification. Results show that Russula is most species-rich at temperate latitudes and ancestral state reconstruction shows that the genus initially diversified in temperate areas. Migration into and out of the tropics characterizes the early evolution of the genus, and these transitions have been frequent since this time. We propose the 'generalized diversification rate' hypothesis to explain the reversed latitudinal diversity gradient pattern in Russula as we detect a higher net diversification rate in extratropical lineages. Patterns of diversification with plant associates support host switching and host expansion as driving diversification, with a higher diversification rate in lineages associated with Pinaceae and frequent transitions to association with angiosperms.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, 332 Hesler Biology Building, Knoxville, TN, 37996-1610, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Looney
authors.affiliation: Department of Organismal Biology, Uppsala University, Evolutionsbiologiskt Centrum, Norbyv. 18D, 75236, Uppsala, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Ryberg
authors.affiliation: Department of Biology, Gent University, K.L. Ledeganckstraat 35, 9000, Gent, Belgium.
authors.forename: Felix
authors.initials: F
authors.lastname: Hampe
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, 332 Hesler Biology Building, Knoxville, TN, 37996-1610, USA.
authors.forename: Marisol
authors.initials: M
authors.lastname: Sánchez-García
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Tennessee, 332 Hesler Biology Building, Knoxville, TN, 37996-1610, USA.
authors.forename: P Brandon
authors.initials: PB
authors.lastname: Matheny
mesh_terms: D001487:Basidiomycota / Q000145:classification*; D005075:Biological Evolution; D002980:Climate; D016000:Cluster Analysis; D004271:DNA, Fungal / Q000235:genetics; D016013:Likelihood Functions; D019684:Magnoliopsida / Q000382:microbiology; D038821:Mycorrhizae / Q000145:classification*; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal
keywords: Russulaceae; fungi; latitudinal diversity gradient; phylogeography; phyloinformatics