鼠兔属两对“近缘种”的分子进化与环境变迁的关系

通过对６种鼠兔限制性内切酶图谱的分析，发现传统的形态学研究公认的两对近缘物种，即高原鼠兔与达乌尔鼠兔及甘肃鼠兔与藏鼠兔实际上来自两个不同的母系群。该结果提示这４种鼠兔两两间彼此形态的相似性可能因趋同进化所致。通过遗传距离计算的各物种分化的时间表明，鼠兔在晚上新世可能有一个快速进化时期。这与在地史上发生的相应的地质事件相吻合。

THE CORRELATION BETWEEN THE ENVIRONMENTAL CHANGES AND THE EVOLUTION OF THE TWO SIBLING SPECIES OF PIKA (GENUS OCHOTONA)

Six species of pika were investigated using mitochondrial DNA (mt DNA) restriction site analysis. The phylogenetic tree was constructed using PAUP with O. erythrotis designated as an outgroup. Perhaps, the most intriguing results of this study is that the molecular tree gives us a different picture of the phylogeny compared with the former morphological studies. Previously, O. cansus and O. thibetana , shrubland burrowing species; O. curzonize and O. daurica , meadow steppe burrowing species have been treated as two pairs of sibling species. Within each pair, the forms have similar morphologies and equivalent ecology. However, with the present study, each pair member is found on a different branch of the tree, which indicates that those forms came from different maternal lineages. Perhaps, the morphological similarities is caused by the convergent evolution. Divergence time, estimated from genetic distances, suggests a period of rapid radiation of genus Ochotona , perhaps during the late Pliocene. These calculations seem to correspond roughly to the tectonic events and environment changes through time, and appear to be substantiated by the fossil record.