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. ***
