The Phylogeny of Pyxidiophora (Ascomycetes)

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Recent studies, including important contributions by Dr. Meredith Blackwell of Louisiana State University, suggest that dispersal of fungal spores by insects and other arthropods is more common than previously thought. With the ascomycetes studied by Blackwell, beetles (including pine bark beetles) and mites have been shown to be critical vectors of spore transport. This information and new knowledge about the complete life histories of these fungi have led to new hypotheses about the evolutionary relationships of arthropod-associated fungi. Because morphological features have not always been helpful in evaluating the taxonomic relationships and phylogeny of these fungi, in large part because of their very small size, Blackwell will incorporate data from molecular analyses of ribosomal gene sequences in her study of evolution. Two general hypotheses about the evolution of these fungi will be investigated. (l) The perithecial ascomycetes associated with arthropods are not a single natural group but represent an assemblage of different evolutionary lines that have converged upon an "insect-transport" system of spore dispersal. (2) The evolution of fungi that are obligate parasites of arthropods has proceeded from ancestors that relied on insects for spore dispersal. The study represents a pioneering combination of traditional mycological techniques of morphology and life-history investigation along with modern molecular methods of genome analysis.