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Systematics and Natural History of the Millipede-Parasitic Genus Myriophora Brown (Diptera: Phoridae)


Myriophora is a near globally distributed species-rich genus whose members are parasitoids of toxic, chemically defended millipedes. Prior to this study, only eight species were described, little was known about how they interacted with millipedes, and no phylogenetic hypotheses of intrageneric relationships had been proposed, resulting in a wide range of available directions to pursue understanding the natural history of Myriophora. The approach taken here is primarily from a systematics standpoint of understanding species level diversity, distribution, and relationships, but with the intent of layering on data from field observations and experiments to not only increase basic biological knowledge of Myriophora but to also then inform and enhance the primary systematics goals. To make feasible taxonomic headway under the time constraint of a Ph.D. project, the taxonomic revision focused only on the New World taxa, resulting in the description of 57 new species, covering a geographic area from Argentina to Canada. Several experiments were carried out aimed at determining how Myriophora locate millipedes. After concluding that the secretions are used as the long-range cue for host-finding, individual components of the benzoquinone blend were tested for attractiveness, and it was found that of the two predominate quinone components in the defensive blend of juliform millipedes, 2-methoxy-3-methyl-1,4-benzoquinone alone attracts adult flies of both sexes, and that a combination of 2-methoxy-3-methyl-1,4-benzoquinone and 2-methyl-1,4-benzoquinone increased attractiveness. Finally, to understand these findings in an evolutionary context, morphological and molecular character data were used to estimate the phylogeny of Myriophora. We find that the ancestral area of Myriophora is the New World and a single dispersal event to the Old World likely occurred via a Beringian connection before subsequently spreading to the Afrotropical Region. The ancestral host reconstructed for Myriophora is the benzoquinone-producing Juliformia, and this association has been conserved in the Old World clade. Species of Myriophora associated with the cyanide-producing millipedes are restricted to a single New World clade.

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