GENE EXCHANGE BETWEEN AFRICAN MALARIA VECTORS

从医学角度来看，冈比亚按蚊复合体可以说是最重要的昆虫类群；它是非洲乃至全世界疟疾的主要传播媒介。这些项目的目标是了解这个群体的进化遗传学；这包括了解物种间不育屏障的遗传基础和物种间基因交换的动力学。先前的研究表明，两个亲缘关系很近的物种可能在自然界中通过杂交交换遗传物质，这种现象被称为基因渐渗。但似乎并不是一个物种基因组的所有部分都能跨越物种边界。利用遗传标记（微卫星），我们打算直接测试基因组的哪些部分负责不育障碍。这将通过进行种间杂交，将每个物种的可育杂交雌性与雄性回交，评估回交后代的生殖状态，并对至少24个均匀分布在基因组中的微卫星进行基因分型来完成。当确定造成不育的区域时，将通过增加微卫星标记的密度来进行更精细的制图。在一项相关研究中，我们将确定基因组的哪些部分能够在自由繁殖的回交种群中持续存在长达20代。第二个项目涉及渗透的动态。特别是，这种渗透是一种古老的现象还是一种最近的、正在进行的过程的问题将得到解决。该项目将包括染色体倒位的DNA序列检查，即第二条染色体左臂的“a”倒位（2La），这是物种间转移的良好证据。这种反演的历史将通过系统发育程序和与数据最一致的渗入事件数量的统计分析来确定。了解世界上两种最重要的疟疾媒介(a。冈比亚和安哥拉。Arabiensis)正在进行基因交换，这对于针对这些物种的控制措施至关重要。

From a medical perspective, the Anopheles gambiae complex is arguably the most important group of insects; it is the primary vector of malaria in Africa, and hence the world. The goal of these projects is to understand the evolutionary genetics of the group; this includes understanding the genetic basis of sterility barriers between species and the dynamics of gene exchange between species. Previous research has indicated that two closely related species may be exchanging genetic material by hybridizing in nature, the phenomenon known as introgression. But it appears that not all parts of a species genome are equally able to cross species boundaries. Using genetic markers (microsatellites) we intend to directly test which parts of the genome are responsible for sterility barriers. This will be done by making interspecific crosses, backcrossing fertile hybrid females to males of each species, assessing the reproductive status of the backcross progeny, and genotyping them for at least 24 microsatellites spread evenly across the genome. When regions responsible for sterility are identified, finer scale mapping will be done by increasing the density of microsatellite markers. In a related study, we will determine which parts of the genome are able to persist in freely breeding backcross populations for up to twenty generations. The second project concerns the dynamics of introgression. In particular, the question of whether the introgression is an ancient phenomenon or a recent, ongoing process will be addressed. This project will involve examination of DNA sequences in a chromosome inversion, the "a" inversion of the left arm of the second chromosome (2La), for which there is good evidence of interspecies transfer. The history of this inversion will be determined using phylogenetic procedures and statistical analysis for the number on introgression events most consistent with the data. Understanding whether the two most important vectors of malaria in the world (An. gambiae and An. arabiensis) are exchanging genes is vitally important to control measures aimed at these species.