Date of Award
Doctor of Philosophy
Ecology and Evolutionary Biology
Randall Small, Jessy Labbe, Sharon Jean-Phillipe, Jen Schweitzer
Phylogenetics is a powerful tool used for illuminating the diversity of life on Earth, their evolution and their ecology. I created a multi-gene phylogenetic tree of Cortinarius section Cortinarius and uncovered five previously overlooked species, increasing the number of species in the section from seven to twelve. All members of the clade possess both cheilocystidia and pleurocystidia and possess a pigment known as (R)-39,49-dihydroxybphenylalanine. Ancestral state reconstruction estimated that the ancestral host was most likely an angiosperm, switching hosts when encountering novel host species in new lands, and only C. violaceus associating with the Pinaceae in North America. Biogeographic analysis found it was most likely that the group originated in Australia, dispersed through long-distance dispersal to South America, where it switched hosts to certain members of the Fabaceae, diversified with Quercus in Central America, then migrated into North America. The test the ‘secotioid’ hypothesis, I performed a phylogenetic logistic regression correlating environmental variables with the state of being sequestrate. ‘Mean diurnal temperature’ and ‘mean maximum temperature in the hottest month’ were significant in estimating the probability of being sequestrate. None of the precipitation variables were significant. A world map of the distribution of sequestrate specimens included in this study show the sequestrate taxa being present in temperate areas and absent from the tropics, in concordance with the finding that sequestrate taxa are found in habitats variable temperatures. This study brings in doubt that moisture is the sole driving force for the evolution of sequestrate taxa.
Harrower, Emma, "Systematics and Biogeography of the Cortinarius violaceus group and Sequestrate Evolution in Cortinarius (Agaricales). " PhD diss., University of Tennessee, 2017.
Available for download on Saturday, December 15, 2018