• Phthiraptera;
  • ectoparasites;
  • systematics;
  • birds;
  • passerines;
  • cytochrome oxidase I;
  • elongation factor-1α;
  • cospeciation

Lice (Insecta: Phthiraptera) are often considered a model group of parasites for studies of cospeciation because of their high host specificity, and louse species in the genus Brueelia are relatively host-specific. To test the extent of cospeciation, we reconstructed a phylogeny for Brueelia from nuclear (EF1α) and mitochondrial (COI) DNA sequences. This phylogeny was generally well resolved and supported. Two major clades within Brueelia (as well as several other lineages) were identified, and these corresponded to major morphological differences in the preantennal region of the head and sclerotization of the abdomen. However, the phylogeny of Brueelia showed little concordance to a published phylogeny of the hosts. In addition, we uncovered four cases (out of 15 species) of one species of Brueelia on two or more bird species. We argue that the high dispersal capabilities of Brueelia species, e.g. phoresis on hippoboscid flies, are a likely explanation for the incongruence between host and parasite phylogenies in this case. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society 2002, 77, 233–247.