Fieldhouse D, Golding G B
Department of Biology, McMaster University, Hamilton, ON, Canada.
Genome. 1996 Oct;39(5):909-13. doi: 10.1139/g96-114.
Rodents are thought to have relatively high rates of evolution, twice as fast as the rates for mammals in other orders. However, the uniformly high rates of evolution inferred for the order Rodentia from Mus musculus and Rattus norvegicus are not consistently found for other rodent species. Using a maximum likelihood phylogenetic algorithm (DNAML), we show here that Mus spicilegus has a fivefold different rate of evolution in 1100 bp around the adenine phosphoribosyltransferase gene (APRT) since its divergence from a common ancestor with Mus musculus. A greater than threefold difference in rates is also found in a comparison of the number of evolutionary events directly detected from the APRT sequences of these two closely related Mus species. The evolutionary events can be directly detected, since M. spicilegus, M. musculus, and the four rodent outgroup species used to determine the ancestral sequence are so closely related. One of the major differences between M. spicilegus and M. musculus that might affect evolutionary rate is the degree of commensalism with man. The Mus species therefore provide a useful model for testing various hypotheses for the causes of rate variations between genes, and possibly, between lineages.
啮齿动物被认为具有相对较高的进化速率，是其他目哺乳动物进化速率的两倍。然而，从小家鼠和褐家鼠推断出的啮齿目统一的高进化速率，在其他啮齿动物物种中并未一致发现。使用最大似然系统发育算法（DNAML），我们在此表明，自小家鼠从与东方田鼠的共同祖先分化以来，东方田鼠在腺嘌呤磷酸核糖转移酶基因（APRT）周围1100 bp的进化速率相差五倍。在对这两种近缘小家鼠物种的APRT序列直接检测到的进化事件数量进行比较时，也发现速率差异超过三倍。由于东方田鼠、小家鼠以及用于确定祖先序列的四个啮齿动物外类群物种关系非常密切，因此可以直接检测到进化事件。东方田鼠和小家鼠之间可能影响进化速率的一个主要差异是与人类共生的程度。因此，小家鼠物种为检验关于基因间，以及可能在谱系间速率变化原因的各种假设提供了一个有用的模型。
