Dissertation Research: Phylogeny, Cospeciation, and Life History Evolution in the Cedar Apple Rust Fungi (Gymnosporangium, Pucciniaceae)

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This study investigates evolutionary patterns in the cedar apple rust fungi. These parasites have a complex life cycle in which they alternately live on two different plant species in order to reproduce. The factors that direct and constrain the evolution of new species of cedar apple rust are not well understood. This study seeks to understand the importance of three crucial aspects of parasite evolution in this group. These are cospeciation, in which a parasite evolves new species in tandem with its host plant, the evolution of life cycle complexity, and the degree of specialization on particular host species.Rust pathogens cause major damage worldwide to such important crops as wheat, soybeans, and coffee. Cedar apple rusts in particular cause damage to fruit trees such as apples, pears, and quince. The evolution of new and virulent species of rusts is of particular concern. This study will increase understanding of evolutionary processes in rusts and the cospeciation and character analyses will have broad relevance in understanding fungal-plant relations and plant parasitism. The study will include Japanese as well as North American species of cedar apple rust. The collaborative ties with Japanese scientists that have been established will serve to promote the expansion and exchange of knowledge on plant pathogenic fungi.