Genetical and chromosomal differentiation in the Nelima genufusca group (Arachnida, Opiliones) and dynamics of the hybrid zones.

为了推断黑褐叶蜂（Nelima nigricoxa）、黑褐叶蜂（N.sp.）和黑褐叶蜂（N.sp.）的核型分化过程，对黑褐叶蜂100多个居群进行了染色体调查。作为参考，属于佐藤组的另外两个物种（佐藤青蟹和青木青蟹）的一些种群也进行了核型分析。结果表明，佐藤组的两个种和Nelima sp.（Ezonami）的染色体数目分别为16和22。而黑角叶蜂和褐角叶蜂的染色体数目变异范围较大，分别为2n=16-22和2n=18-22。核型的外群比较和地理分布格局均表明，在两个种的分布范围内，其数目依次减少。2n=19的个体在杂交群体（2n=20/19/18 a：戴森北方坡川户）中的频率显著低于Hardy-Weinberg定理的期望值（p<0.02）。这表明在2n=20和18 a之间杂种的适合度下降，这可能是杂种区狭窄的部分原因。2n= 19的杂合子没有发现精子发生障碍的证据。为了从基因水平上估计16、18 a和20 3种不同核型小种间的分化程度，测定了6个黑腹叶蜂居群的细胞色素氧化酶1（Cytochrome oxidase 1，CO 1）基因片段的碱基序列。在310 bp的6个位点中，在具有3种不同核型的群体中发现了碱基的替换。现在使用限制性内切核酸酶进行更详细的比较。

To infer the differentiation processes of karyotypes in three species of the genufusca-group, Nelima nigricoxa, N.sp. (tentatively called Ezonami-zatomushi in Japanese), and N.genufusca, chromosomal survey has been made for more than 100 populations of the group. As a reference, some populations of two additional species (Nelima satoi and N.aokii) belonging to the satoi-group have also been karyotyped. As a result, the numbers of chromosomes were found to be 16 and 22 for two species of the satoi group and Nelima sp. (Ezonami), respectively. On the other hand, Nelima nigricoxa and N.genufusca showed a wide range of variation in the chromosome number : 2n=16-22 and 2n=18-22, respectively. Both the outgroup comparison and geographic patterns of distribution of the karyotypes suggest that the number successively decreased within the ranges of both species.A hybrid zone found in western part of Tottori Prefecture, Honshu was analyzed in detail. Frequency of the individuals with 2n=19 in the hybridized population (2n=20/19/18a : Kawadoko on the northern slope of Mt.Daisen) was significantly lower than the expected value from Hardy-Weinberg's theorem (p<0.02). This indicates decrease of fitness in hybrids between 2n=20 and 18a and in turn it may partly account for the narrowness of the hybrid zone. However, no evidence of disorder in the spermatogenesis was obtained for the heterozygotes with 2n=19.To estimate the degree of differentiation at the genic level among races with three different karyotypes (16,18a, and 20), the sequences of bases of the DNA fragments of the Co1 (cytochrome oxidase 1) were determined for six populations of Nelima nigricoxa. In six sites out of 310 bp, substitutions of the bases were found among populations with three different karyotypes. More detailed comparison using restriction endonucreases is now undertaken.