Reinterpreting the origins of flamingo lice: cospeciation or host-switching?

The similarity of the louse faunas of flamingos and ducks has been used as evidence that these two groups of birds are closely related. However, the realization that ducks actually are more closely related to Galliformes caused many workers to reinterpret this similarity in parasite faunas as host switching from ducks to flamingos. Recent unexpected phylogenetic results on the relationships of waterbirds and their lice call for a reinterpretation of the origins of the lice of the enigmatic flamingos. Here, we bring together new evidence on the phylogenetic relationships of flamingos and their lice and show that the lice of flamingos and grebes areclosely related because their hosts share a common ancestor (cospeciation). We also demonstrate that the similarity of the louse faunas of flamingos and ducks is a result of host switching from flamingos to ducks, rather than from ducks to flamingos.