Evolution of reproductive traits and speciation process : approaches with experimental hybridization, genomic analysis and mathematical models

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In this study, we have focused on a ground beetle group Ohomopterus in Japan, which consists of 15 species with marked interspecific diversity of genital morphology. We analyzed the genetic basis of interspecific difference in genital morphology between two Ohomopterus ground beetles using a quantitative genetic and QTL mapping approach. In the quantitative genetic analysis, it was inferred that relatively small number of genes produced the large difference in genitalia between 0. iwawakianus and 0. maiyasanus. We also conducted a QTL mapping with F2 hybrids of these species using AFLP and microsatellite markers. We analyzed evolutionary trend of genital morphology in relation to other reproductive traits using a comparative method, and found that exaggeration of genital morphology occurred in association with spermatophore size and copulation time. In addition, we analyzed shape of sperm and sperm-bundles which can be selected for improvement of sperm-competition ability. We found a d … More imorphism of sperm-bundles, i.e. long and short types, in most species and revealed that long sperm bundles have been evolved in association with other reproductive traits including genital parts. The evolution of genital morphology is considered to have occurred within populations through sexual selection and could have contributed to mechanical reproductive isolation which promotes speciation. A similar effect is expected for differentiation in body size. Using interspecific mitochondrial gene flow as an index of intrgressive hybridization, we revealed that differences in genital and body sizes had effect to prevent introgressive hybridization. Besides the above studies, we also studied the effect of cuticular hydrocarbon (CHC) on mate recognition and variation in CHC among species to explore the potential role of CHC as sexual pheromones to enable coexistence of closely related species. In addition, the pattern and strength of pre-and post-mating reproductive isolation between various pairs of Ohomopterus species. Less