Phylogenetic analysis of the Degeeriella complex (Insecta: Phthiraptera): The problem of defining genera of lice based on the classification of their hosts.

Lice genera have historically been defined based on taxonomic groupings of their hosts. While some of these are natural groups, molecular phylogenies have shown that many of these genera are not monophyletic. Using 1 mitochondrial and 3 nuclear genes we inferred a phylogeny for 115 taxa (from all genera) within the Degeeriella complex to investigate the relationships among taxa in this group. This complex contains 16 louse genera parasitizing a wide range of birds including raptors, woodpeckers, gamebirds, and toucans. The resulting phylogeny showed that many currently recognized genera are not monophyletic. In some instances these newly identified lineages more accurately reflect higher level bird classification, for example Degeeriella itself was found to actually comprise two distantly related lineages, one infesting Falconiformes whereas the other is found on Accipitriformes, agreeing with the recent findings that these two groups of predatory birds are not closely related. Conversely, Picicola chewing lice parasitizing woodpeckers, which have traditionally all been placed in this single genus, form multiple geographically limited lineages. However, woodpecker host phylogenies have confirmed that these hosts are monophyletic.There are also instances where lice from unrelated hosts are members of a well-supported monophyletic clade indicating a history of intraordinal host-switching. For example, lice from rollers, a group of Old World coraciiform are embedded within Degeeriella from hawks (Accipitriformes). Members of the Degeeriella complex are known to disperse via phoresis (hitchhiking) on hippoboscid flies, which could explain the apparently plethora of intraordinal an intrafamilial host-switches found in this group of parasites.