Budget Amount *help 
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1996 : ¥1,100,000 (Direct Cost : ¥1,100,000)

Research Abstract 
To reveal the nature and formation process of chromosomal hybbrid zones in Nelima nigricoxa, we analyzed karyotypes, allozymes, and mtDNA for various populations of the species and the closely related congeners. A total of seven karyotypes were recongnized in Nelima nigricoxa : 2n=20 (Kyushu, Shikoku, and Chugoku district westward of the Asahi River), 2n=18a (West of Mt.Daisen, Tottori Pref.and Kinki district), 2n=18b (north of Okayama city), 2n=16 (Chugoku mountains eastward from the Asahi River), 2n=22a (IzuHakone), 2n=22b (Miura Peninsula), 2n=22c (Mt.Kiyosumi, Chiba Pref.). Of these, each of the three adjoining karyotype pairs (2n=20/18a, 2n=18a/16, and2n=16/18a) forms a hybrid zone with a width less than 13 km. In a population (Shimimudani) in a hybrid zone between 2n=16 and 18a in Sekiganecho, Tottori Prefecture, the ratio of individuals with 2n=17 chromosomes was significantly lower than the expected ratio from the HardyWeinberg theorem (<0.02). The relative fitness of indi
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viduals with 2n=17 was 0.4 when taking 2n=16 equals 1. The figure was much lower than the relative fitness of heterozygotes, 0.7 obtained in a population (Kawadoko) in a hybrid zone (2n=18/20) in Mt.Daisen. Difference in the size of chromosomes that pertain to the chromosome rearrangement may explain this result. We analyzed sequences of about 1 kilobase pairs of CO I gene coded by the mtDNA for several population of N.nigiricoxa and some populations of the closest relatives. The phylogeny obtained was : (nigricoxa Mt.Kiyosumi, Chiba, 2n=22, genufusca Sapporo, 2n=22) (genufusca Tokusen Falls, Yamaguchi, 2n=22 (nigricoxa Tokusen Falls, Yamaguchi, 2n=20 (nigricoxa Mt.Senjo, 2n=18 (nigricoxa Makiyaha Mt.Daisen 2n=20, nigricoxa 2n=20 Makihara Mt.Daisen)))) and the bootstrap probability for each branch was 100% without exception. It was confirmed that grographic differentiation can be detected also in mtDNA level among some morphologically nondifferentiatied populations of Nelima nigricoxa in the Chogoku district. Less
