| In order to better understand parasite diversification, I went to the Galapagos Islands to study the ecology and evolution of a model bird-parasite system, which included four phylogenetically independent ectoparasite lineages infecting the Galapagos Hawk (Aves: Buteo galapagoensis). The parasites comprised two lice (Insecta: Phthiraptera: Amblycera, Ischnocera), a lousefly (Diptera: Hippoboscidae) and an avian skin mite (Acari: Epidermoptidae). Ultimately, my goal was to examine ectoparasite evolutionary epidemiology and disease susceptibility in relation to the host's ecological and colonization history.;At the outset, I hypothesized that parasite natural history was key in influencing the coalescent process. Accordingly, I found differences in prevalence, abundance and degree of aggregation among each hawk ectoparasite species. I proposed using parasite population genetics to infer host history as a new rationale for parasite conservation. In that context, a DNA barcoding approach revealed predictable differences in transmission rates of two Galapagos dove (Zenaida galapagoensis) louse genera to hawks during predation events. A 'generalist' mite species from Galapagos hawks and Flightless cormorants (Phalacrocorax harrisi) comprised two cryptic species, one of which was structured genetically between two hawk island populations. The hawk amblyceran and lousefly harbored less population genetic structure than the ischnoceran, which was more differentiated than the host, although isolated populations of both lice contained unique, fixed haplogroups, illuminating cryptic parasite diversity and restricted host gene flow among islands. This variation, however, was only related to host genealogy in the ischnoceran and the rate of molecular evolution was faster in the ischnoceran than in the host. Among islands, hawk inbreeding explained louse infection intensity and natural antibody levels, and the latter was inversely related to amblyceran louse abundance, which encounters the host immune system.;Separately from the ectoparasite work, I collaborated on a characterization of Avipoxvirus isolates from Galapagos birds, showing significant recombination among pox strains, and we recovered Haemoproteus -like parasites from multiple seabird species on Genovesa. Finally we showed that a vector of avian disease was established on Isla Santa Cruz (Culex quinquefasicatus). This study was the first to examine host-parasite evolutionary epidemiology within the Galapagos avifauna, one of the most intact and threatened island bird communities. |
