Preliminary Analysis of Population Differentiation of Culex tarsalis in Montana Using Microsatellites

Abstract

West Nile virus, an arbovirus classified in the genus Flaviviridae, presents a serious threat to humans and horses in Montana. The virus, first isolated in the West Nile district of Uganda in 1937, spread rapidly across the United States after its initial introduction to New York in 1999. In 2003 there were 222 human cases of West Nile in Montana. The overarching goal of the Carroll College West Nile virus study is to create a risk assessment map for the state of Montana. This will bring better awareness to the risk of West Nile infection based on geographic location and time. The specific goal of this project was to use microsatellite data to assess the genetic differentiation of the mosquito vector, Culex&tarsalis, between study sites across the state of Montana, and to evaluate if populations separated by greater geographic distance have higher FST values than those located closer together. Multiplex and individual locus PCR methods were used to amplify five microsatellite loci. HE (heterozygosity) values for each population were obtained, and FST values were obtained for betweenWpopulation comparisons. My hypothesis that FST values increase as geographic distance increases was not supported. Harlem and Medicine Lake had a lower FST than Medicine Lake and Bowdoin, which are separated by a smaller geographic distance. Three factors – small sample sizes, high frequencies of null alleles, and deviations from HardyW Weinberg equilibrium – are almost certainly confounding the data, making meaningful conclusions largely unfeasible to draw.