Evolution of Phoresy and Feeding Associations in the Mite Order Parasitiformes

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ABSTRACT The origin of parasitism is one of the enduring questions in biology. Because parasitism has arisen multiple times among mites, they are an excellent taxon in which to study this phenomenon Mites show also many other types of associations, allowing hypotheses on transitions among diverse types of associations. Phoresy is of particular interest, as it is a common phenomenon in mites. In this type of association one organism (a mite) uses another organism (insect or vertebrate) to move from one place to another. It does not involve feeding on the host, or development during the period of transport. Various authors have proposed that phoresy might be a precursor to feeding associations such as parasitism, and the goal of this project is to test that idea. The test group is the mite order Parasitiformes, the smaller of the two mite orders, currently including about 77 families. Testing the phoresy to parasitism hypothesis can be done by determining whether lineages that are parasitic nest within lineages that are phoretic, a pattern predicted under this hypothesis. This approach requires good knowledge of historical relationships, but unfortunately, knowledge of such relationships in this group is incomplete. A large part of the project is therefore devoted to deriving well supported hypotheses of relationships within Parasitiformes. This will be done using a combination of morphological and molecular data. Molecular data consist of sequence data for parts of the 18S and 28S nuclear ribosomal RNA genes, and the nuclear protein coding gene Elongation Factor 1-alpha.This group is of general biological interest in part because it includes ticks of medical importance and the economically important bee parasite Varroa. Both parasitism and phoresy are common within Parasitiformes making it a good candidate for this project. By providing rigorous hypotheses of relationships among Parasitiformes, this research will improve our understanding of numerous ecologically, medically, and economically important mites and make this group of mites available as a model system for broad questions in evolutionary biology.