Phylogeny, host association and biogeographical patterns in the diverse millipede-parasitoid genus Myriophora Brown (Diptera: Phoridae).

Abstract

Myriophora is the most species-rich group of parasitoids that attack toxic, chemically defended millipedes in the superorder Juliformia and order Polydesmida-a resource that few insect predators and parasitoids are able to exploit. Worldwide, there are an estimated 200 species of Myriophora, with the majority of the diversity centred in the Neotropical region. The phylogeny of Myriophora is unknown, biogeographical patterns are not documented, and known host associations have not been assessed in a phylogenetic context. We provide the first phylogenetic study of the genus from a data set composed of 52 taxa primarily from the Neotropical region including 10 outgroups, 40 morphological characters, and molecular data from three mitochondrial (16S, COI and ND1) and one nuclear marker (AK). We find that Myriophora dispersed from the New World to the Old World in a single event before subsequently spreading to the Afrotropical region. The ancestral hosts reconstructed for Myriophora are the benzoquinone-producing Juliformia, and this association has been retained in the Old World clade. In the Neotropical region, Myriophora that are associated with cyanide-producing polydesmidan millipedes are confined to a single clade that shows remarkably little genetic variation between clearly morphologically diagnosable species.