| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
After allopatric speciations, interspecific interactions through hybridization and resource competition during secondary contacts will affect their distribution ranges and evolution of traits which are related with reproductive isolation and niche segregation. Coexistence of multiple closely related species will be achieved through repeated allopatric speciation and secondary contacts. Communities of closely related species show several patterns in morphological differentiation which is possibly correlated with prezygotic reproductive isolation and/or resource partitioning. We analyzed two cases of hybridizations between closely related carabid beetles of the subgenus Ohomopterus (genus Carabus). First, between Carabus maiyasanus and C.iwawakianus, parapatric distribution has been maintained with an intervening narrow hybrid zone. We found that males cannot discriminate heterospecific females before copulation, and interspecific copulation often resulted in death of females and breaks
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of male genitalia because of the great difference in genitalic morphologies. F1 hybrids emerged showed intermediate genitalic morphologies between parental species. Second, a supposed hybrid population (C.insulicola pseudinsulicola) was studied, with probable parent populations of C.insulicola insulicola and C.arrowianus nakamurai. Again, the parent species could not discriminate heterospecifics before copulation. F1 hybrids were raised to adults which showed a morphology similar to the supposed hybrid species. Further rearing should confirm F1 beetles are fertile and can maintain a hybrid lineage. A preliminary analysis of mtDNA gene sequences indicated gene flows among the above populations. These results suggested that the evolutionary process leading to sympatric, well-segregated species involves different qualities of secondary contacts, such that initial divergence of two species in morphologies which are related with prezygotic reproductive isolation is sufficiently large enough to prevent their sexual competition and formation of fertile hybrids. Less
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