9629716 Wade Speciation, the splitting of one species into two, is a basic process in biology. It occurs when two populations become genetically different enough that they cannot produce fertile offspring. This project studies the genetic basis for this reproductive isolation in two species of flour beetles, Tribolium castaneum and T. freemani, which produce sterile offspring when crossed. In crosses among different strains of these species, there is variation in the proportion of offspring that are female and the frequency of deformed males. Genetic crosses and selection experiments will be used to investigate the genetic basis for these differences. These experiments address how selective forces and genetic variation within a species result in enough divergence for reproductive isolation and speciation. Studying the genetic basis for speciation is fundamental for understanding the generation of species biodiversity.