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

目的：探讨黑毛线虫（Nelima nigricoxa， N.sp.）属三种植物核型的分化过程。（在日语中暂时称为Ezonami-zatomushi）和n.s genufusca，对该群体的100多个种群进行了染色体调查。作为参考，本研究还对satoi属的另外两个种（Nelima satoi和n.a aokii）进行了核型分析。结果发现，satoi组和Nelima sp. （Ezonami）的两个物种的染色体数分别为16和22。另一方面，黑毛线虫和genufusca的染色体数目差异较大，分别为2n=16-22和2n=18-22。外群比较和核型分布的地理模式都表明，在这两个物种的范围内，数量依次减少。对在本州鸟取县西部发现的一个杂交带进行了详细分析。杂交群体（2n=20/19/18a: Kawadoko in Mt.Daisen北坡）中2n=19的个体出现频率显著低于Hardy-Weinberg定理的期望值（p<0.02）。这表明在2n=20和18a之间，杂种的适合度下降，这可能部分解释了杂交带狭窄的原因。然而，对于2n=19的杂合子，没有发现精子发生障碍的证据。为研究3种不同核型（16、18a和20）的小种在基因水平上的分化程度，测定了6个黑线虫居群的细胞色素氧化酶1 (Co1) DNA片段的碱基序列。在310bp的6个位点中，在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.