Doctor of Philosophy
Date of Defense
Parasites exhibit a wide range of life history strategies that contribute to different dispersal abilities, host specialization, transmission modes, life-cycle complexity and population structure. Understanding dispersal rates in hosts and parasites is instrumental in defining the scale at which coevolution may be occurring. In order to better understand how and when parasites move between different hosts, I studied a seabird – Hippoboscid fly ectoparasite (and vector) – Haemosporidian parasite system in the Galapagos Islands. I began by describing the Haemosporidian parasites of Galapagos seabirds, discovering a Plasmodium species parasite in Galapagos Penguins (Sphensicus mendiculus), and a new clade of Hippoboscid-vectored parasites belonging to the subgenus Haemoproteus infecting frigatebirds (Fregata spp.) and gulls (Creagrus furcatus). Despite strong genetic differentiation between Galapagos frigatebirds and their conspecifics, we found no genetic differentiation in their Haemoproteus parasite. This led me hypothesize that the movement of the Haemosporidian parasite was facilitated by the movement of the Hippoboscid fly vector. In order to answer this question, I used a comparative population genetic study of Galapagos Great Frigatebirds (F. minor), Nazca Boobies (Sula granti), and their respective Hippoboscid fly parasites (Olfersia spinifera, O. aenescens) to better understand movement of flies at the geographic scale of the archipelago. I found high levels of gene flow in both fly species, despite marked differences in the degree of population genetic structure of their bird hosts. This suggests that host movement, (and therefore parasite movement), is not necessarily associated with true host dispersal, where dispersal is followed by successful reproduction. Finally, I examined local (within island colony) transmission in the Great Frigatebird, Haemoproteus iwa, Olfersia spinifera system. I inferred movement, or host-switching, by analyzing host (frigatebird) microsatellite markers run on DNA amplified from the fly. Using the most variable microsatellite markers, we are able to identify host genotypes in bloodmeals that do not match the host from which the fly was collected. Flies that were not infected with H. iwa were more likely to have a bloodmeal that did not match the genotype of their host and female birds were the more likely recipients of host-switching flies.
Levin, Iris Ilena, "Host-parasite interactions in Galapagos seabirds" (2012). Dissertations. 362.