Geographic Pattern of the Microsatellite DNA Polymorphism in two species of Sorex shrew in Hokkaido

基于线粒体细胞色素b基因核苷酸序列的种内和种间系统发育，研究了生活在日本列岛及其邻近地区的6种鼩鼱的生物地理历史。利用核糖体RNA基因（rDNA）的限制性片段长度多态性（RFLP）研究了种间或种群间的系统发育关系，以期更详细地推断出美洲棘猴和爪棘猴的生物地理历史。利用微卫星DNA标记检测遗传群体结构。rDNA-RFLP分析表明，北海道种群与欧亚种群的遗传距离较远，库页岛种群起源于大陆种群与北海道种群的杂交。在北海道大陆种群中，微卫星位点存在较大的遗传变异。等位基因丰富度和杂合度与岛屿大小成正比，与地理距离呈显著正相关，而北海道大陆各地方种群间与地理距离无显著正相关。这表明在北海道的最终种群扩张发生在长爪沙鼠身上，早于短爪沙鼠身上。结合rDNA-RFLP、微卫星DNA和mtDNA cyt-b等信息，推断出北海道地区的S. unguiculatus和S. caecutiens的生物地理历史：末次冰期前入侵北海道的Sorex caecutiens，由于其林间性，在末次冰期最盛时期，北海道地区以草原植被为主，因此被限制在北海道南部的森林保护区。但在冰期后，随着北海道森林植被的恢复，其活动范围逐渐扩大。北海道的爪蟾入侵时间晚于爪蟾，可能是在最后一个冰河时代的鼎盛时期，并很快分布在北海道各地，在寒冷气候下不仅栖息于南部森林保护区，还栖息于草原。少

The biogeographic history of six soricine shrew species inhabiting the Japan archipelago and neighboring regions has been studied based on intra- and interspecific phylogeny of nucleotide sequences of mitochondrial cytochrome b gene.To infer biogeographic histories of S. caecutiens and S. unguiculatus in more detail, phylogenetic relationships between species or populations were investigated by restriction fragment length polymorphism (RFLP) for the nuclear ribosomal RNA genes (rDNA). Genetic population structures were examined using microsatellite DNA markers.From the rDNA-RFLP analysis, it was suggested in S. caecutiens that Hokkaido population is genetically distant from Eurasian ones and Sakhalin population originated from hybridization between the continent and Hokkaido populations.High genetic variations in microsatellite loci were observed among Hokkaido mainland populations of both species. The allelic richness and heterozygosity were proportional to the island size and positiv … More e correlation between genetic and geographic distances was detected in S. unguiculatus, while S. caecutiens showed no positive correlation between genetic and geographic distances among local populations in Hokkaido mainland. This implies that the final population expansion in Hokkaido occurred in S. unguiculatus earlier than in S. caecutiens.Combining the information from rDNA-RFLP, microsatellite DNA and mtDNA cyt-b, biogeographic histories of S. unguiculatus and S. caecutiens in Hokkaido were inferred as follows: Sorex caecutiens, which invaded Hokkaido before the last glacial age, was restricted to the forest refuge in southern Hokkaido because of its sylvicolous nature, at the maximum stage of last glacial age, where grassland vegetation prevailed in Hokkaido. However, it expanded its range with recovery of forest vegetation all over Hokkaido in post glacial age. S. unguiculatus invaded Hokkaido later than S. caecutiens, probably at the maximum stage of last gracial age, and soon came distributed throughout Hokkaido inhabiting not only the southern forest refuge but also grasslands prevaily under the cold climate. Less