Yasuda Shumpei P, Gamage Chandika D, Koizumi Nobuo, Nishio Sanae, Isozumi Rie, Shimizu Kenta, Koma Takaaki, Amada Takako, Suzuki Hitoshi, Yoshimatsu Kumiko, Arikawa Jiro
Department of Microbiology, Hokkaido University Graduate School of Medicine.
Genes Genet Syst. 2014;89(2):71-80. doi: 10.1266/ggs.89.71.
We examined genetic variation in black rats (the Rattus rattus complex) from Kandy District, Sri Lanka using mitochondrial cytochrome b (cytb, 1140 bp) and nuclear melanocortin 1 receptor (Mc1r, 954 bp) gene sequences together with database sequences. We confirmed the existence of two divergent mitochondrial lineages in Sri Lankan black rats, with genetic distance of 2.2% and estimated divergence time of 0.3 million years ago. Because one lineage is unique to the island and the other is closely related to R. rattus populations on the Indian subcontinent, two migration events of R. rattus from the subcontinent are inferred, one ancient and one recent. Mc1r analyses revealed 12 haplotypes among the Sri Lankan black rats. A median-joining network together with other available sequences separated the 12 haplotypes into two groups, one unique to the island and the other related to previously reported R. rattus sequences. Notably, most individuals possessed various combinations of both haplotype groups which had no association with the cytb clades. These results imply that old and new R. rattus lineages are now intermingled as a result of hybridization in Sri Lanka. Specimens of the lesser bandicoot rat (Bandicota bengalensis) collected from Sri Lanka (n = 24) were shown to have no genetic variability in the cytb sequence. Our results indicate that the two most abundant groups of commensal rats in Sri Lanka, black rats and lesser bandicoot rats, are the product of contrasting evolutionary histories on different timescales.
我们利用线粒体细胞色素b（cytb，1140 bp）和核黑素皮质素1受体（Mc1r，954 bp）基因序列以及数据库序列，对来自斯里兰卡康提区的黑鼠（黑家鼠复合体）的遗传变异进行了研究。我们证实了斯里兰卡黑鼠中存在两个不同的线粒体谱系，遗传距离为2.2%，估计分歧时间为30万年前。由于一个谱系是该岛屿特有的，另一个与印度次大陆的黑家鼠种群密切相关，因此推断黑家鼠有两次从次大陆的迁移事件，一次是古代的，一次是近代的。Mc1r分析揭示了斯里兰卡黑鼠中有12种单倍型。一个中介连接网络以及其他可用序列将这12种单倍型分为两组，一组是该岛屿特有的，另一组与先前报道的黑家鼠序列相关。值得注意的是，大多数个体拥有两个单倍型组的各种组合，这些组合与cytb分支没有关联。这些结果表明，由于在斯里兰卡的杂交，黑家鼠的新旧谱系现在相互混杂。从斯里兰卡收集的24只小竹鼠样本在cytb序列中没有遗传变异。我们的结果表明，斯里兰卡两种数量最多的共生鼠类，黑鼠和小竹鼠，是不同时间尺度上对比鲜明的进化历史的产物。
