Molecular Studies of Cospeciation in a Host-Parasite Assemblage

宿主-寄生虫组合中共物种的分子研究

• 批准号: 9527583
• 负责人: Mark Hafner
• 金额: $ 14万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-07-01 至 2000-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9527583&HistoricalAwards=false
• 关键词: Molecular; Studies; Cospeciation; Host; Parasite

9527583 HAFNER Despite considerable study, biologists still know very little about relative rates of DNA change in distantly related groups of organisms, such as mammals versus insects. In this research, Mark Hafner and Xuhua Xia will investigate a host-parasite system, from which they will generate comparative data about rates of DNA change. The hosts in this study are pocket gophers, which are small, herbivorous rodents found throughout much of North and Central America. The parasites are chewing lice, which are small, ectoparasitic insects that live in the fur of their hosts. The association between chewing lice and their hosts is considered obligate, because the lice cannot survive off their natural hosts. This intimate and long-term association between pocket gophers and chewing lice presents an unusual opportunity to examine both the pattern and rate of molecular change in the DNA of these organisms. Previous work has shown that each speciation event in the pocket gophers is accompanied by a speciation event in their lice. This means that one can measure the amount of molecular change between the species of lice that live on these gophers. Since time is a constant, such a comparison yields a direct measure of relative rates of DNA change in the gophers versus their lice. Sequences of two mitochondrial genes (cytochrome oxidase I and cytochrome b) will be used to construct independent phylogenies of gophers and lice. These trees will be compared statistically to evaluate overall branching similarity, hence degree of cospeciation in the gopher-louse assemblage. Finally, lengths of homologous branches in the gopher and louse trees will be compared to determine relative rates of DNA change in gophers versus lice.

尽管有大量的研究，生物学家仍然对远亲生物群体的DNA变化的相对速率知之甚少，例如哺乳动物与昆虫。 在这项研究中，Mark Hafner和Xuhua Xia将研究宿主-寄生虫系统，从中他们将产生关于DNA变化率的比较数据。 这项研究中的宿主是囊地鼠，这是一种小型的食草啮齿动物，遍布北美和中美洲的大部分地区。 这些寄生虫是咀嚼虱，这是一种生活在宿主皮毛中的小型体外寄生昆虫。 咀嚼虱和它们的宿主之间的联系被认为是专性的，因为虱子不能在它们的自然宿主中生存。 囊地鼠和咀嚼虱之间这种亲密而长期的联系为研究这些生物体DNA中分子变化的模式和速率提供了一个不寻常的机会。 先前的研究表明，囊地鼠的每个物种形成事件都伴随着虱子的物种形成事件。 这意味着人们可以测量生活在这些地鼠身上的虱子物种之间的分子变化量。 由于时间是一个常数，这样的比较产生了一个直接的测量相对速度的DNA变化的地鼠与他们的虱子。 两个线粒体基因（细胞色素氧化酶I和细胞色素B）的序列将被用来构建地鼠和虱的独立染色体。 这些树将进行统计比较，以评估整体分支的相似性，因此在地鼠虱子组合的共同物种形成的程度。 最后，将比较地鼠和虱子树中同源分支的长度，以确定地鼠与虱子的DNA变化的相对速率。