Date of Award
Doctor of Philosophy
Elliot S. Krafsur
Tsetse flies transmit trypanosome species that cause sleeping sickness in humans and nagana in livestock. In the absence of a vaccine against trypanosome parasites and given the high cost of treatment, vector control remains the most effective method for reducing the incidence of trypanosomiasis. In anticipation of area-wide control of G. pallidipes by using genetic methods, a thorough understanding of its breeding structure is required.;Capture release-recapture data show that G. pallidipes has a high capacity for dispersal, but genetic data indicate surprisingly high differentiation among populations. Studying local patterns of genetic variation and examining how such variation changes temporally can provide insight into the apparent contradiction between ecological and genetic data. The overall objective of my research was to determine microgeographic (200 m--≤10 km) genetic structure of G. pallidipes and compare with population structure at the macrogeographic (tens to hundreds of kilometers) scale. In addition, I wanted to assess temporal changes in gene diversity and differentiation.;Microsatellite DNA loci were characterized and used to study genetic variation within and among natural G. pallidipes populations. The loci were highly polymorphic (mean number of alleles = 20.5 +/- 10.1) and unlinked hence useful for population studies. Mating was random within but not among populations at the macrogeographic scale (F ST = 0.18). Differentiation among microgeographic populations was minimal (FST = 0.017) indicating a high rate of gene flow at microgeographic scale. Allele frequencies were homogeneous among sampling sites. Analysis of molecular variance (AMOVA) showed that most of the variation (>90%) lay within sites while only 2% of the total variance was attributed to variation among blocks.;Allele frequencies were homogenous between seasons. Genetic differentiation was higher in the dry season than in the wet season. However, differentiation between pooled wet and pooled dry season samples did not differ significantly from zero (FST = 0.008, G ST = 0.004). AMOVA showed that less than 2% of the variance could be attributed to difference between temporal samples. It is concluded that tsetse populations show little temporal variation probably due to drift. These results provide a better understanding of levels of genetic subdivision and gene flow at the local scale.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
Johnson Ouma Odera
Odera, Johnson Ouma, "Population genetic studies of the tsetse fly, Glossina pallidipes (Diptera: Glossinidae) " (2004). Retrospective Theses and Dissertations. 1189.