Phylogenetics and host-specificity of the mega-diverse louse genus Myrsidea (Amblycera: Menoponidae)

Myrsidea Waterston is the most diverse genus of chewing lice, primarily parasitizing perching birds (Passeriformes), which is the most speciose avian order. Myrsidea also parasitize several hosts from non-passerine groups, including toucans, barbets, woodpeckers (Piciformes) and hummingbirds (Apodiformes). To examine host specificity, host switching and generic limits, we reconstructed a phylogeny of the avian feather louse genus Myrsidea using DNA sequence data from two fragments of the mitochondrial COI gene and a fragment of the nuclear EF-1 alpha gene for 152 Myrsidea specimens collected from 23 avian host families. Unlike other highly diverse louse genera, only a small proportion of Myrsidea species parasitize more than one host species. We found that host family has significant phylogenetic signal on the Myrsidea phylogeny. These results suggest that Myrsidea is generally highly host-specific, with some exceptions where host switching is important. We found that there are two separate groups of Myrsidea that parasitize toucans, and that both are nested within Myrsidea found on perching birds, suggesting that these toucan ectoparasites may have arisen from two independent host switching events. Lastly, representatives of the genus Ramphasticola Carriker, which was originally described as a distinct genus due to a suite of morphologically unique characters, falls in with a strongly supported clade of Myrsidea parasitizing Ramphastos toucans, and therefore we definitively place Ramphasticola as a synonym of Myrsidea.