Abstract
How speciation occurred has always been an intriguing and mysterious issue to evolutionary biologists. Pre-mating isolation exhibits an evolutionary force to prevent gene exchange in natural populations but the detailed mechanism is difficult to study in the laboratory. Drosophila melanogaster provides an opportunity to examine an incipient speciation process because of the divergent mating preference between different races. Zimbabwe females, under multiple-choice conditions, mate only with males from the same race whereas elsewhere females show weak preference. This behavior system raises several interesting issues such as the existence of other isolation mechanism, the underlying genetics of this sexual isolation system, and the precise traits for female recognition. In this study, first, I would like to know if other factors maintain this sexual isolation. M female preference and the aggressiveness of Z male courtship were identified via different behavioral assays. Analyses of male courtship also showed that the mating isolation is bi-directional. Second, through comparison of the cuticular hydrocarbon profiles between Z and M populations and perfuming assays, males’ cuticular hydrocarbon profiles are first identified traits responsible for Z females’ recognition. Finally, in order to find the genes related to this incipient speciation, several differentially expressed genes were identified using subtractive hybridization and cDNA microarrray experiments. All of these genes are candidates as speciation genes and worthy for further study. Through different experiment designs, we could obtain more information about this pre-mating isolation system.