Congruence and cospeciation: Morphological and molecular phylogenetics of the Amblycera (Phthiraptera)

Lice (Phthiraptera) are highly host-specific, permanent ectoparasites of birds and mammals. Their long association and close ecological relationship with their hosts is considered to facilitate the cospeciation (or parallel cladogenesis) of louse and host taxa. The high degree of topological congruence that has been found between the phylogenies of some lice (Ischnocera: Trichodectidae) and their hosts, has led to their recognition as the definitive example of cospeciation. However, further empirical studies of this phenomenon in other groups of lice are hampered by a lack of parasite phylogenies. Here, the phylogeny and cospeciation of a suborder of chewing lice (Phthiraptera: Amblycera) with their hosts is investigated.The first phylogeny reconstructed solely for amblyceran genera is presented. This study, based on an extensive comparison of adult morphology and a rigorous cladistic analysis, considers generic exemplars from 4 families of amblyceran lice (Menoponidae, Boopiidae, Laemobothriidae and Ricinidae). The monophyly and evolutionary relationships of these families are strongly supported and there is good support for the Menoponidae and Boopiidae as sister taxa. The relationships of the families are not concordant with the traditional hypothesis of a basal Menoponidae. The study identifies 4 supra-generic groups within the Menoponidae, which are discussed with reference to previous classifications and studies which have included amblyceran taxa. A preliminary assessment of host-parasite cospeciation is also provided. Whether a similar phylogeny would be produced from molecular data is investigated. The relationships of genera based on morphology are compared with phylogenies generated from the nuclear gene elongation factor 1a and the mitochondrial gene cytochrome oxidase I. Different methods of reconstruction used to assess their phylogeny and raw signal find that the data are largely incongruent, although there is little support for the topologies generated from the sequence data. The monophyly and relationships of families are compared between the datasets and differences in rate heterogeneity between the data are also discussed. A first phylogeny for the genus Austromenopon (Amblycera: Menoponidae) and their close allies (based on the results of the morphological analysis) is reconstructed from molecular data using the mitochondrial genes COI and 12S rRNA. The molecular phylogenies obtained are generally incongruent, with most branch support located nearer the tips of the tree. No analysis recovered a monophyletic Austromenopon, although there is good support for a subset of the Austromenopon taxa, which repeatedly group together. The combined molecular phylogeny for the lice is subsequently compared with a phylogeny constructed for their seabird hosts (Aves: Charadriidae, Laridae, Phaethontidae, Phalacrocoracidae, Procellariidae, Scolopacidae and Sulidae), to evaluate the relative contributions of cospeciation and other processes in the host-parasite association (i.e. duplications, sorting events and host-switching). A significant level of cospeciation is found. A quantitative comparison with results found for another suborder of chewing lice (Phthiraptera: Ischnocera) on similar birds, concludes that both amblyceran and ischnoceran lice have similarly cospeciated with their hosts. However, theamblyceran lineage has undergone more host-switching and less duplication and sorting events than ischnoceran lice. The ecological reasons for these different patterns of host association are discussed.