The population genetics of pathogenic fungi
Fundyga, Ruth Elizabeth
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Pathogenic fungi are important causes of morbidity and mortality in immunocompromised patients, and agricultural pathogens cause millions of dollars in crop loss annually. This dissertation describes the empirical population genetic structure of Candida albicans and mathematically examines the population structure of diploid fungi in general. Thirteen populations of C. albicans were genetically surveyed using 5 microsatellite loci. Surprisingly, the two United States populations were most divergent, but they were also from blood stream isolates. Previous studies that did not use population genetic methods found no association between source of isolate and genotype. The third chapter describes the effect of clone correction, a common data analysis procedure, on the perception of population structure. Clone correction is the process of counting a genotype once no matter how often it appears in the sampled population and is performed to avoid bias due to sampling of related individuals. Clone correction alone can drive Wright's FIS away from 0, even when the initial population is randomly mating. Further, its effects on individual loci are varied but can be large. Clone corrected data should be interpreted with caution alongside the uncorrected data. The fourth chapter is a mathematical analysis of the effects of clonal, sexual, and parasexual reproduction on allele frequencies. Even when parasexual and/or clonal reproduction represents 99% of all reproduction, allelic disequilibria will decay nearly to 0 in 10 generations.