Long-distance dispersal and speciation of Australasian and American species of Cortinarius sect. Cortinarius.

Abstract

We present a multigene phylogeny (partial nuc rDNA and RPB2) of Cortinarius sect. Cortinarius (i.e. the C. violaceus group), which reveals eight species distributed in Europe, Australasia, South America, Central America and North America. Relaxed molecular clock analyses suggested that diversification began during the Miocene, thus rejecting more ancient Gondwanan origin scenarios among the taxa currently occurring in the northern and southern hemispheres. There was strong support for an Australasian origin of the C. violaceus group with initial dispersal to the Neotropics, followed by migration into North America and Europe. A dispersal-extinction cladogenesis model that includes a parameter for founder effects was the most highly supported biogeographic model in the program BioGeoBEARS. A maximum likelihood analysis showed the most recent common ancestor of sect. Cortinarius was an angiosperm ectomycorrhizal associate. Ancestral associations at the plant family level, however, were ambiguous. Of eight recovered species-level lineages, C. violaceus is the only one that associates with Pinaceae and the only species to associate with both Pinaceae and angiosperms. This analysis showed that long-distance dispersal and founder event speciation have been important factors during evolution of the C. violaceus group.