The cantharelloid clade: dealing with incongruent gene trees and phylogenetic reconstruction methods

Abstract

We reassessed the circumscription of the cantharelloid clade and identified monophyletic groups by using nLSU, nSSU, mtSSU and RPB2 sequence data. Results agreed with earlier studies that placed the genera Cantharellus, Craterellus, Hydnum, Clavulina, Membranomyces, Multiclavula, Sistotrema, Botryobasidium and the family Ceratobasidiaceae in that clade. Phylogenetic analyses support monophyly of all genera except Sistotrema, which was highly polyphyletic. Strongly supported monophyletic groups were: (i) Cantharellus-Craterellus, Hydnum, and the Sistotrema confluens group; (ii) Clavulina-Membranomyces and the S. brinkmannii-oblongisporum group, with Multiclavula being possibly sister of that clade; (iii) the Sistotrema eximum-octosporum group; (iv) Sistotrema adnatum and S. coronilla. Positions of Sistotrema raduloides and S. athelioides were unresolved, as were basal relationships. Botryobasidium was well supported as the sister taxon of all the above taxa, while Ceratobasidiaceae was the most basal lineage. The relationship between Tulasnella and members of the cantharelloid clade will require further scrutiny, although there is cumulative evidence that they are probably sister groups. The rates of molecular evolution of both the large and small nuclear ribosomal RNA genes (nuc-rDNA) are much higher in Cantharellus, Craterellus and Tulasnella than in the other cantharelloid taxa, and analyses of nuc-rDNA sequences strongly placed Tulasnella close to Cantharellus-Craterellus. In contrast analyses with RPB2 and mtSSU sequences placed Tulasnella at the base of the cantharelloid clade. Our attempt to reconstruct a “supertree” from tree topologies resulting from separate analyses that avoided phylogenetic reconstruction problems associated with missing data and/or unalignable sequences proved unsuccessful.

• Basidiomycota
• Fungi
• mtSSU
• nLSU
• nSSU
• phylogeny
• RPB2

This work was made possible by the U.S. National Science Foundation Research Coordination grant 0090301 to M. Blackwell, J.W. Spatafora and J.W. Taylor. Support of JMM was from the Canadian Natural Science and Engineering Research Council, the Canadian Foundation for Innovation and the Royal Ontario Museum. Support for RHN was from the Helge A son Johnson, Anna and Gunnar Vidfelt and Lart Hierta foundations in Sweden. SD was supported from the U.S. National Science Foundation Microbial Observatory grant0348689 during completion of this work and was assisted by Maribeth Latvis in the laboratory. Michael Wood and Roy Halling provided images for Fig. 2.