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

9902259哈里森和卡尔的共生现象描述了自然界中两个或两个以上的物种生活在一起的情况，通常但不一定是为了双方的利益。共生体被认为是维持自然多样性和生态系统正常运作的重要因素。尽管如此，关于共生的重要问题仍然是开放的，包括：1）物种如何联合形成共生; 2）共生在促进多样性方面的作用是什么？为了帮助回答这些问题，研究生蒂莫西卡尔在康奈尔大学的理查德哈里森博士的指导下，正在研究一组苍蝇（Asteromyia属）及其共生的成胆真菌（通常被置于Macrophoma属）的分类学和系统发育关系，以及这种关系所涉及的生态因素。昆虫和它们的共生真菌是研究共生问题的有价值的系统，因为昆虫和真菌的基因组现在已经足够好的遗传分析，因为这两组分类群都适合实验室实验。从这个苍蝇真菌系统的初步证据表明，有许多隐藏的或神秘的苍蝇和真菌物种参与，因为苍蝇和真菌物种可能是无法区分的形态，但遗传分歧。来自核和线粒体基因的DNA序列的数据将被用来识别存在的苍蝇和真菌的谱系以及它们之间的关系。遗传数据也将用于确定真菌的近亲;感兴趣的是它们是否与昆虫共生，或者它们是否具有其他生态作用。拟议的研究还涉及生态实地研究和实验，将比较共生关系对不同种类的苍蝇和真菌的影响。一种可能性是，共生关系是一个互利共生的一些苍蝇真菌对，但在其他情况下，没有物种受益或一个物种受到负面影响。

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.