Diversification of ectomycorrhizal (ECM) fungi

Symbiotic relationships are widespread and ecologically important, and they may be considered evolutionary advantageous, as they provide access to newly unexplored ecological resources. The ECM symbiosis has evolved numerous times across the fungal and land plant tree of life with no known reversals to their ancestral, saprotrophic state. This association increases the efficiency in the acquisition of nutrients in plants, while providing carbon to the fungi, which can consequently allow both partners to allocate more resources into growth and improve fitness.

I evaluated whether the ECM mode is a key innovation that promoted diversification within the suborder Tricholomatineae. I tested this by inferring the nutritional mode of members of this suborder using stable isotope ratio techniques to predict the source of carbon and nitrogen of these taxa. I hypothesized that the independent origins of ECM mode, represent evolutionary key innovations that promoted species to diversify at a higher rate than non-ECM lineages. Overall, this hypothesis is not fully supported since only two out of six lineages of ECM fungi (Tricholoma and the Rhodopolioid clade of Entoloma) show an increased rate in diversification. These results suggest that other factors such as wide geographic distribution or high plant host diversity may promote diversification in these clades, Tricholoma has a cosmopolitan distribution and forms ECM associations with a wide variety of hosts including angiosperms and gymnosperms. Diversification in the Rhodopolioid clade could be due to the unique combination of spore morphology and ECM habit. The spore morphology may represent an exaptation that aided spore dispersal and colonization. This is the first study to investigate rate shifts across a phylogeny that contains both non-ECM and ECM lineages.

Relevant publications:

  1. Sánchez-García M, Matheny PB. (2017) Is the switch to an ectomycorrhizal state an evolutionary key innovation in mushroom-forming fungi? A case study in the Tricholomatineae (Agaricales). Evolution 71: 51-65
  2. Looney BP, Ryberg M, Hampe F, Sánchez-García M, Matheny PB. (2016) Into and out of the tropics: global diversification patterns in a hyperdiverse ectomycorrhizal fungal lineage. Molecular Ecology 25: 630-647
  3. Sánchez-García M, Henkel TW, Aime MC, Smith ME, Matheny PB. (2016) Guyanagarika, a new ectomycorrhizal genus of Agaricales from the Neotropics. Fungal Biology 120(12): 1540-1553 

Systematics of the suborder Tricholomatineae

The suborder Tricholomatineae contains three families: Entolomataceae, Lyophyllaceae and Tricholomataceae, as well as many other incertae sedis genera. I focused part of my doctoral dissertation on the study of the family Tricholomataceae, which in the past included 98 genera of white-spored mushrooms. After a molecular systematic evaluation, I reduced this family to 7 genera (Tricholoma, Porpoloma, Leucopaxillus, Dennisiomyces, Albomagister, Corneriella, and Pseudotricholoma).

Another part of my doctoral dissertation focused on the description of a new ectomycorrhizal genus from the Pakaraima Mountains of Guyana. This new genus called Guyanagarika contains three cryptic species and is part of the Catathelasma clade, which was formally recognized as an expanded family Biannulariaceae that includes the genera Callistosporium, Catathelasma, Guyanagarika, Macrocybe, Pleurocollybia and Pseudolaccaria.

I am in the process of describing new species of Tricholomataceae from the Southern Appalachian Mountains. Stay tuned to know more about those new taxa.

Relevant publications:

  1. Sánchez-García M, Matheny, B, Palfner G, Lodge DJ. (2014) Deconstructing the Tricholomataceae and introduction of the new genera Albomagister, Corneriella, Pogonoloma and Pseudotricholoma. Taxon 63(5): 993-1007
  2. Sánchez-García M, Henkel TW, Aime MC, Smith ME, Matheny PB. (2016) Guyanagarika, a new ectomycorrhizal genus of Agaricales from the Neotropics. Fungal Biology 120(12): 1540-1553 
  3. Raj KN Anil, Latha KP Deepna, Sánchez-García M, Manimohan P. (2015) A new species of the genus Corneriella from India supported by morphological and molecular data. Phytotaxa 213(2): 102-112

Systematics of the genus Melanoleuca

This research aimed to reconstruct a molecular phylogeny of the genus Melanoleuca using sequences from two nuclear ribosomal gene regions (ITS, LSU) and one single copy nuclear protein-coding gene (RPB1) from a number of specimens collected in America and Europe. These datasets were analyzed in order to assess the phylogenetic position of Melanoleuca and to evaluate the taxonomic, ecological, and geographical boundaries that can be useful for species delimitation. The results support Melanoleuca as a monophyletic group and its inclusion in the Pluteoid clade, being the sister group of Pluteus. I also found that the cystidia (sterile cells found on the hymenium of some basidiomycetes) are important characters to recognize major lineages. I described four new species distributed in America (M. communis, M. herrerae, M. jaliscoensis, and M. longisterigma), showing that European names have been widely misapplied to similar-looking species in America.

Relevant publications:

  1. Sánchez-García M, Cifuentes-Blanco J, Matheny PB. (2013) Taxonomic revision of the genus Melanoleuca in Mexico and description of new species. (Original title: Revisión taxonómica del género Melanoleuca en México y descripción de especies nuevas). Revista Mexicana de Biodiversidad 84 (suplemento micologia): S111-S127