TAXONOMIC DIVERSITY AND INTERACTIONS OF INSECT-ASSOCIATED ASCOMYCETES

Many ascomycetes are associated with insects to form symbioses. The fu ngi are necrotrophic and biotrophic parasites, endosymbionts, insect-d ispersed forms, and other obligate associates that provide nourishment for insects. Diversity among these fungi can be categorized in severa l different ways: taxonomic diversity, variety of interaction types oc curring within a fungal lineage, and number of fungal species. Previou sly our inability to produce well supported phylogenetic hypotheses ha s obscured these views of diversity. Over the past 5 years our knowled ge of insect-associated fungi has been improved by the use of DNA sequ ence analysis. Such studies have revealed that ascomycetes in almost a ll major clades are associated intimately with insects. Of particular interest has been the sorting out of relationships of taxa with conver gent morphologies, unique characters, and lost characters, including t hose associated with sexual reproduction. Within some fungal groups th e types of interactions with insects are diverse, and eventually phylo genetic analysis will help to trace the evolutionary development of sy mbioses. Molecular studies also contribute to our understanding of the number of species which may vary according to species concepts used i n their study.