XVI International Botanical Congess

By mapping characters to gene trees, I am studying evolutionary patterns in the Ascomycota. Ancestral ascomycetes may have been hyphal saprophytes on plant materials, reproducing sexually as outcrossers, with a dikaryotic state but no croziers. More recently, some ascomycetes became parasites, and some became selfers, or apparently, lost sexuality. In collaboration the G. Turgeon I am using housekeeping and mating type genes to for a more detailed analysis of life style change, in the genus Cochliobolus (Pleosporaceae, Ascomycota). In Cochliobolus, heterothallic sexuality is the ancestral condition and 'asexual' species and homothallic species are nested among heterothallic sexual species. Mating type gene sequences appear to evolve quickly between species but to be conserved within species, and may contribute to species delimitation.