Phylogenetic Analysis of Biogeography, Habitat and Host Associations in Ticks

9420658只黑蜱是一种专性的体外寄生螨类，以各种各样的陆地脊椎动物为食。它们通常被认为具有高度的宿主特异性，这导致了扁虱和它们的宿主之间平行物种形成的假设。然而，初步分析表明，这种表面上的特异性可能是人为的：被记录为只有一到两个宿主的物种往往是那些不常见或罕见的物种，而宿主范围似乎随着收集的更多而增加。因此，应考虑替代机制，例如通过地理分离形成物种，或为不同的非寄主生境制定专门性。收集的关于分布和寄主组合的信息的初步调查结果符合这种机制；它们还支持Aargasid属的Otobius和Cario的新世界起源，以及可能的Gonwaana起源的硬蜱属。在这些群体中，似乎有专门针对洞穴或特定类型鸟巢的谱系。这项研究要检验的假设是，可以解释为寄主可获得性的次要结果，即寄主可获得性由非寄主生境和地理位置的专一性决定。若要检验这一假说，就需要更好地解决壁虱分类群的系统发育关系。形态和分子系统分析，利用16S和12S线粒体rDNA以及COI和COII线粒体蛋白编码基因，已经开始在不同的分类水平上提供良好的系统发育支持。该项目的研究将继续进行这种分子系统发育分析，并将这些数据与形态信息相结合，集中在硬蜱属硬蜱与鸟类和蝙蝠软蜱之间的关系。这些群体是检验这一假设的理想选择，因为它们是世界性的，在宿主和栖息地的偏好上表现出广泛的范围。目前正在完成一个广泛的计算机化数据库，包括寄主、栖息地和扁虱物种的地理分布，用于检验这一假说。这个项目将通过澄清扁虱的识别和分类，帮助我们了解地球上的生物多样性。这些以血液为食的体外寄生虫一直是疾病的媒介，因此对许多脊椎动物种群的水平施加了控制。最近，他们因为包括莱姆病的媒介而臭名昭著，莱姆病使人虚弱，最终是致命的，并已蔓延到美国大部分地区。***

9420658 BLACK Ticks are obligate ectoparasitic mites feeding on a wide variety of terrestrial vertebrates. They have generally been believed to be characterized by high levels of host specificity which has led to the assumption of parallel speciation between ticks and their hosts. However, a preliminary analysis suggests that this seeming specificity might be an artifact: species recorded as having only one or two hosts tend to be those that are uncommon or rare, while host range seems to increase as more collections are made. Alternative mechanisms, such as speciation through geographical separation or the development of specificity for different off-host habitats, should therefore be considered. Initial results from investigation of collection's information on distributions and host associations fit such mechanisms; they also support a New World origin for the argasid genera Otobius and Carios and a possible Gondwana origin of the genus Ixodes. Within these groups there appear to be lineages specialized for caves or for specific types of bird nests. The hypothesis to be examined in this study is that the perceived pattern of host associations in ticks can be explained as a secondary result of host availability determined by specificity for off-host habitats and geography. Well resolved phylogenetic relationships for tick taxa are needed to test this hypothesis. Morphological and molecular systematic analysis, using the 16S and 12S mitochondrial rDNA and COI and COII mitochondrial protein coding genes, has already begun to provide well supported phylogenies at various taxonomic levels. The research of this project will continue such molecular phylogenetic analysis and integrate those data with morphological information, concentrating on relationships among hard ticks in the genus Ixodes and soft ticks on bird and bats. These groups are ideal for testing the hypothesis because they are cosmopolitan and exhibit a wide range in host and habitat preferences. An extensive computerized d ata base on host, habitat, and geographic distribution of tick species is currently being completed for use in testing this hypothesis. %%% This project will contribute to our understanding of the earth's biodiversity by clarifying identification and classification of ticks. These blood-feeding ectoparasites have always been disease vectors and thereby imposed controls on the levels of many vertebrate populations. Most recently they have gained major notoriety for including the vector of Lyme disease, which is debilitating, ultimately fatal and has spread throughout most of the United States. ***