My research interests are in the field of evolutionary genetics, especially in processes occurring at or influenced by the genome. Active research projects in the lab are primarily concerned with using the fly species Drosophila americana to understand the factors influencing chromosomal change and the mechanisms involved in the differentiation of sex chromosomes. Changes in chromosomal arrangement are common, but their significance is unknown. We are currently examining a chromosomal rearrangement involving a centromeric fusion of the X chromosome and an autosome in D. americana. This derived arrangement exists as a polymorphism with the ancestral arrangement, showing a strong latitudinal cline in the central and eastern US. Population genetic analyses are used to examine the hypothesis that these alternative chromosomal arrangements coordinate adaptive genetic variation. Independently evolved pairs of sex chromosomes exhibit similar patterns of differentiation. The Y chromosome is genetically inert, and the X chromosome contains many active unique genes and often compensates for differences in dosage between genders. The X-4 centromeric fusion in D. americana provides a system for examining the earliest asymmetries between newly evolved sex chromosomes. We are testing models of sex chromosome evolution by examining patterns of sequence variation on this pair of neo-sex chromosomes.