Speciation, karyotypic differentiation, and hybrid zones in the Gagrellula ferruginea-group (Arachnida, Opiliones)

铁锈菌Gagrellula ferruginea-group由三个种组成(G.ferrugina、G.grais、G.sp.)，在种间和种内都表现出很大的核型变异。研究了核型分化的地理模式和染色体杂交带在该群体物种形成过程中的作用。主要结果如下：(1)铁棉的染色体数为2n=10~24，棉属为2n=18~20。大葛为2n=20。其中，铁锈菌在核型和外部形态上的变异最大，在该类群中分布最广。基本没有发现核型分化与外部形态之间的密切联系。(2)在本州岛北部Kink区的Tango山周围地区，铁皮棉染色体数目的多样性最大，其数目在2n=14~20之间，在染色体数目不同的两个群体相邻的每一个点上都有一个杂交带。(3)两个地理小种(九州-广岛小种和大伊塞斯小种)在广岛县西部相遇，范围略有重叠。在重叠区，腿与身体的相对长度在两个种族之间存在显著差异，表明角色移位的发生。(4)两个染色体数目不同的地理群体虽然往往不完全，形成了杂交带，但都或多或少地表现出合子前生殖隔离。

The Gagrellula ferruginea-group, consisting of three species (G.ferruginea, G.grandis, G.sp.), shows great karyotypic variability both between and within species. Geographical patterns of the karyotype differentiation and the role of the chromosomal hybrid zones in the speciation process of the group were investigated. The principal results obtained are as follows : (1) The number of chromosomes ranged from 2n=10 to 24 in G.ferruginea, 2n=18-20 in G.sp. and 2n=20 in G.grandis. Of these, G.ferruginea, occupying the widest ranges in the group, was most variable in both karyotypes and external morphology. Basically, no close association was found between differentiations in karyotypes and external morphology. (2) G.ferruginea showed greatest diversity in chromosome number in the area surrounding Tango Mountains in northern Kink district, Honshu ; where the number ranges from 2n=14 to 20. At the every points where two populations with different chromosome numbers abut, a hybrid zone was always found. (3) Two geographic races (Kyushu-Hiroshima race and Daises race) of "Gagrellula ferruginea" meet in the western of Hiroshima Prefecture, with a slight overlap of their ranges. In the overlap zone, relative length of legs to body significantly differed between the two races ; indicating occurrence of character displacement. (4) It was found that two geographical populations with different chromosome numbers show prezygotic reproductive isolation more or less, though it is usually far from complete and hence hybrid zones are formed.