Dissertation Research: Effect of phoretic dispersal on the structure of parasite populations

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By comparing differences in the population genetic structure of parasites that disperse in different ways, this study will determine how increases and decreases in dispersal influence that structure. Understanding how and why populations are structured is a major goal of evolutionary biologists because the resulting population genetic structure affects rates of local adaptation, speciation and extinction. This study will examine the population genetic structure of lice that live on the feathers of pigeons. Natural populations are typically subdivided, or genetically structured, because geographic or ecological factors influence the chance that two individuals will mate. One major factor that influences population genetic structure is dispersal, the movement of individuals from one place to another. When individuals disperse to new populations, they mate with individuals in the new population reducing population genetic structure. We know little about how dispersal affects the magnitude of this structure. Host-parasite systems offer highly tractable systems with which to study how different modes of dispersal influence population genetic structure. This study will do so by examining population genetic structure of different parasite species that are located on the same host individuals. In addition, this study will produce an inquiry-based activity aimed at middle-school students, "Hitchhikers guide to the city: Lessons from lice," and will contribute to the training of graduate and undergraduate students.In this study, researchers will use a pigeon-louse, host-parasite system to investigate how population genetic structure differs between two species of parasitic feather lice (Order: Phthiraptera) that differ in their ability to disperse. The study will investigate the role of vertical dispersal and horizontal dispersal in structuring the populations of wing lice and body lice that occur on Rock Pigeons (Columba livia). Although these lice are ecologically very similar, wing lice can disperse phoretically using flies, whereas body lice do not. Despite the pervasiveness of phoresy, the affect that this dispersal mechanism has on the population structure of these organisms is unknown. Researchers will use a nested sampling design to collect lice from different host individuals, in different flocks, in different regions of the world. They will sample in regions where flies are present, and where flies are not present and phoresis cannot occur. They will use microsatellite data to determine the relative role of vertical and horizontal-phoretic dispersal in structuring louse populations.