Bugrov A G, Warchałowska-Sliwa E, Tatsuta H, Akimoto S
Novosibirsk State University, Institute for Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia.
Folia Biol (Krakow). 2001;49(3-4):137-52.
The grasshopper Podisma sapporensis consists of two main chromosome races in Hokkaido. The western group of populations of P. sapporensis, belonging to the XO race, has a diploid number of chromosomes 2n = 23 in the male and 2n = 24 in the female (sex determination XO male/XX female). The eastern group of populations of this species, belonging to the XY race, differs from the western one as a result of Robertsonian translocation between the originally acrocentric X chromosome and M5 autosome in homozygous state, having resulted in the forming of chromosome sex determination neo-XY male/neo-XX female (2n = 22). These races are geographically isolated by the mountainous system consisting of the Mts Daisetsu and Hidaka range, occupying the central part of the island. The hybrid zones between the races have not so far been discovered. Various levels of polymorphism for the pericentric inversions and C-banding variation exist in different chromosomes throughout populations in both chromosome races. In some solitary populations (the population at the summit of Mt Yotei, populations in the vicinity of Naganuma, Oketo, and Tanno) pericentric inversions are fixed in some pairs of chromosomes, which enables marking of the discrete karyomorphes. In the Mt Daisengen population all chromosomes are two-armed as a result of fixing the pericentric inversions. These facts contradict karyotypical conservatism of the tribe Podismini. The level of diversity of P. sapporensis karyotypes could provide a new perspective on the evolutionary process of different karyotype in Orthoptera. The considerable occurrence of polymorphism in chromosomes suggests that karyotypic diversification is undergoing in P. sapporensis. The authors also proposed that P. sapporensis would be divided into four chromosome subraces in the XO chromosome race and two chromosome subraces in the XY race, on the basis of karyotypic features. These races may have been established by fundamental climatic changes during the glacial epoch.
北海道的北海道笨蝗（Podisma sapporensis）由两个主要染色体族组成。属于XO族的北海道笨蝗西部种群，雄性的二倍体染色体数为2n = 23，雌性为2n = 24（性决定方式为XO雄性/XX雌性）。该物种属于XY族的东部种群，由于原本的近端着丝粒X染色体与纯合状态的M5常染色体之间发生罗伯逊易位，与西部种群不同，导致形成了染色体性别决定方式为neo-XY雄性/neo-XX雌性（2n = 22）。这些族在地理上被由大雪山和日高山脉组成的山地系统隔开，该山地系统占据了岛屿的中部。到目前为止尚未发现各族之间的杂交区。在两个染色体族的整个种群中，不同染色体上存在着不同程度的臂间倒位多态性和C带变异。在一些孤立种群（羊蹄山山顶的种群、长沼、小惠和丹野附近的种群）中，某些染色体对中的臂间倒位是固定的，这使得能够标记离散的核型。在大仙山种群中，由于臂间倒位的固定，所有染色体都是双臂的。这些事实与笨蝗族的核型保守性相矛盾。北海道笨蝗核型的多样性水平可以为直翅目不同核型的进化过程提供新的视角。染色体多态性的大量出现表明北海道笨蝗正在经历核型多样化。作者还根据核型特征提出，在XO染色体族中北海道笨蝗可分为四个染色体亚族，在XY族中可分为两个染色体亚族。这些族可能是在冰川时期由基本的气候变化形成的。
