Patterns of the disposition of chromosomal hybrid zones in several species of harvestmen (Arachnida, Opiliones) in the Kinki District and Shikoku

我们调查了近木地区、本州邻近地区和四国的几种收割机的染色体数目，以获得这些物种染色体杂交区的地理位置信息。最显著的结果是在四国的Gagrellula ferruginea。调查结果如下：香川县高松市南部的二倍体染色体数目从2n=16增加到20，尽管该县东部的居群包括IS，但这些居群的染色体数目是多态的。香川县西部的种群呈多态分布(2n=12/13/14)或单态分布(2n=12)，分布范围与山上2n=20种群的分布范围重叠。龙，没有任何杂交的迹象。这意味着2n=12种群与2n=20种群在生殖上完全隔离。然而，这两种形式通过中间数目的种群(2n=14，16，18)相互交错，在本州中部地区(冈山县和兵库县)三洋一侧两个不同染色体数目的相邻种群毗邻的地区形成狭窄的接触区域。因此，2n=12和2n=20群体的分布范围与两端相连的一系列中间群体的重叠可被认为是由于染色体数目的连续增加(或减少)而产生的环形重叠的情况。

We surveyed number of chromosomes of several species of harvestmen including Gagrellula ferruginea, Nelima nigricoxa, and N.genufusca in the Kinki District and adjacent areas of Honshu, and Shikoku to obtain information on geographical positions of chromosomal hybrid zones of these species. Most notable result was available in Gagrellula ferruginea in Shikoku. The results obtained from the survey were as follows : The diploid number of chromosomes increases from 2n=16 to 20 in the southern part of Takamatsu City, Kagawa Pref., through intermediate populations polymorphic for the number, although populations in eastern part of the prefecture including Is. Shodo invariably showed 2n=16. Populations in the western part of Kagawa Prefecture were polymorphic (2n=12/13/14) or monomorphic (2n=12) and the distributional range of the 2n=12 population overlaps that of the 2n=20 populations in Mt. Ryuo, without any indication of hybridization. This means that the 2n=12 population is reproductively fully isolated from the 2n=20 population. However, both the forms intergrade one another through populations with intermediate numbers (2n=14,16,18), making narrow zones of contact in the areas where two neighboring populations with different chromosome numbers abut in Sanyo side of Chugoku District (Okayama and Hyogo Prefectures), Honshu. Thus, the overlap of the distributional ranges of 2n=12 and 2n=20 populations with a series of intermediate populations connecting both ends can be considered a case of circular overlap that arose from successive increase (or decrease) of chromosome numbers.