Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology

Date of Defense

5-2-2006

Graduate Advisor

Patricia G. Parker, Ph.D.

Committee

Kellogg, Elizabeth A

Marquis, Robert J

Ricklefs, Robert E

Johnson, Kevin P

Abstract

In order to better understand parasite diversification, I went to the Gal¿pagos Islands to study the ecology and evolution of a model bird-parasite system, which included four phylogenetically independent ectoparasite lineages infecting the Gal¿pagos 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 Gal¿pagos dove (Zenaida galapagoensis) louse genera to hawks during predation events. A generalist mite species from Gal¿pagos 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 from Gal¿pagos birds, showing significant recombination among 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 Gal¿pagos avifauna, one of the most intact and threatened island bird communities.

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Biology Commons

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