Malaria parasites have a complex life cycle involving sexual reproduction in the mosquito vector and asexual proliferation in the vertebrate host. Mosquito vectors are therefore the definitive host of the malaria parasite. The literature on avian malaria parasites remains biased towards bird-parasite associations, and avian malaria vectors are not well studied in this system. My dissertation fills a gap in the current body of avian malaria research by using molecular techniques to document 1) patterns in phylogeographic structure of avian Plasmodium across geographic regions; 2) absence of vector specificity in two common mosquito species in Ithaca, New York; and 3) evidence that local vectors amplify a local avian Plasmodium lineage.
In my first chapter, I review our current understanding about the associations between avian malaria vectors and avian Plasmodium. I synthesize this with literature on human malaria-mosquito interactions and mosquito feeding preferences to argue that it is crucial to study vector ecology to understand host-parasite dynamics. Variation in mosquito ecology could help explain patterns observed in avian malaria parasite infection. In chapter 2, I document patterns of phylogeographic structure in Plasmodium parasites sampled across the range of a single bird species. I demonstrate that geographic patterns in parasite lineage distribution are not solely attributable to differences in the parasites found in different bird species. In chapter 3, I describe the avian Plasmodium lineages found in two abundant, local ornithophilic mosquito species and show that parasites sampled from mosquitoes are represented by many diverse cytochrome b haplotypes. The most common of these haplotypes are shared between mosquito species, and overlap only slightly with those previously isolated directly from numerous bird species. In chapter 4, I report results from a feeding experiment using laboratory-reared mosquitoes and wild-caught birds naturally infected with Plasmodium. I examine the variation within Cx. pipiens in its ability to be invaded by the parasite by conducting PCR on individual mosquitoes following incubation with sufficient time to allow the complete digestion of the blood meal and development of sporozoites in the salivary glands.