Evolutionary ecology and molecular phylogenetic analysis of interactions between closely related species

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This study focused on interspecific interactions between the carabidbeetles of the subgenus Ohomopterus (genus Carabus, Carabidae, Coleoptera), which is endemic to Japan and consists of 15 species. In Ohomopterus, there are hybrid zones between parapatric species, especially of Insulicola species group and Yaconinus species group. I analyzedinterspecific hybridization between Carabus iwawakianus and C.maiyasanus, andbetweenC.insulicola andC.arrowianus nakamurai in the laboratory. These pairs differedin the difference in genital characters which affects the cost of interspecific mating. The genital characterswere much different between C.iwawakianus and C.maiyasanus, and the cost at interspecific mating was large enough to maintain theirparapatricdistribution. BetweenC.insulicola andC.a. nakamurai which hada small differencein genital characters, the cost at interspecific mating was small, In the field, hybrid populations were established at intermediate zones of the two species. Thus, interspecific interactions at secondary contacts may contribute both divergence and reticulate speciation in the carabid beetles, depending on the interspecific difference at the contacts. I also studied molecular phylogeny of Ohomopterus by using two mitochondrial genes and five nuclear genes. The results of molecular phylogenetic analysis suggests that hybridizations oftenresultedin introgression of mitochondria, which producedincongruencepatterns between mitochondrial lineage and morphological species. I investigated mitochondrial polymorphisms in four species in central and eastern Honshu, and detecteddirectional introgressions among these species, with evidences for natural hybridizations of corresponding species. This study demonstrated the significance of reticulate events in the evolution of carabid beetles.