Systematics, diversity and evolution of the suborder Tricholomatineae (Agaricales)

The suborder Tricholomatineae is one of the several major groups of Agaricales, the largest order of mushroom-forming fungi. This suborder contains three families: Tricholomataceae, Entolomataceae and Lyophyllaceae, as well as many genera of incertae sedis. Members of the Tricholomatineae exhibit variation in nutritional mode, including mycoparasites, saprotrophs, termite-associates, bryophyte parasites, and ectomycorrhizal (ECM) symbionts, which makes the clade ideal for studying trophic evolution in fungi from a phylogenetic perspective.

This dissertation combines taxonomy and evolutionary analyses to contribute to the knowledge of fungal diversity and mycorrhizal evolution. First, I present a systematic revision of the family Tricholomataceae within a molecular context, including molecular annotations of generic types and other type collections, and reducing this family from 98 to seven genera. Then, I use a multi-gene phylogeny of the suborder Tricholomatineae to test the hypothesis that the ECM symbiosis is a key innovation that promoted species diversification. I find evidence that supports such increases in two of six ECM lineages of the Tricholomatineae. However, no increases in diversification are detected in the other four ECM clades of this suborder. This suggests that diversification of those two clades was not due to the evolution of the ECM lifestyle, and I hypothesize that it could be due to the expansion and dominance of its main hosts and ability to associate with a variety of hosts. Diversification in one of those two clades, the Rhodopolioid clade of the genus Entoloma, could be due to a unique combination of spore morphology and ECM habit. The spore morphology may represent an exaptation that aided spore dispersal and colonization. Finally, I describe a new genus with three new species from the Pakaraima Mountains in Guyana. These taxa are within the Catathelasma clade, which I recognize as the family Catathelasmataceae, that form an independent clade of ECM fungi and the first known case of a Neotropical endemic ECM lineage within the Agaricomycetes.