Dissertation Research: Molecular Systematics of Asteromyia and Macrophoma: Patterns of Association and Divergence in an Insect-Fungus Symbiosis

点击翻译按钮获取中文摘要

9902259Harrison and Carr Symbiosis describes situations in nature where two or more species live together, often, but not necessarily, to the benefit of both. Symbioses are thought to be important in maintaining natural diversity and proper functioning of ecosystems. Nonetheless, important questions about symbioses remain open, including: 1) how do species associate to form a symbiosis; and 2) what is the role of symbioses in promoting diversity? To help answer these questions, graduate student Timothy Carr, under the direction of Dr. Richard Harrison at Cornell University, is examining the taxonomic and phylogenetic relationships of a group of flies (in the genus Asteromyia) and their symbiotic gall-forming fungi (usually placed in the form-genus Macrophoma) and the ecological factors involved in this relationship. Insects and their symbiotic fungi are valuable systems for examining questions about symbiosis because insect and fungal genomes are now sufficiently well known for good genetic analysis and because both groups of taxa are amenable to laboratory experimentation. Preliminary evidence from this fly-fungus system suggests that there are many hidden or cryptic species of fly and fungus involved, because both fly and fungus species may be indistinguishable morphologically but divergent genetically. Data from DNA sequences from nuclear and mitochondrial genes will be used to identify the lineages of flies and fungi present and the relationships among them. Genetic data will also be used to determine the close relatives of the fungi; of interest is whether they are symbiotic with insects or if they have another ecological role. The proposed research also involves ecological field studies and experiments that will compare the effects of the symbiotic relationship on the different species of flies and fungi. One possibility is that the symbiotic relationship is a mutualism for some fly-fungus pairs, but that in other situations neither species benefits or one species is negatively affected.