Omland Kevin E
Department of Biological Sciences, State University of New York at Albany, Albany, New York, 12222.
Department of Zoology, Duke University, Durham, North Carolina, 27708.
Evolution. 1997 Oct;51(5):1381-1393. doi: 10.1111/j.1558-5646.1997.tb01461.x.
Since Zuckerkandl and Pauling (1962, 1965) proposed the molecular clock, many studies seem to have supported their prediction that rates of molecular and morphological evolution generally will be decoupled. Most of these studies were aimed at taxa in which rates of morphological evolution were thought to vary greatly a priori. For the current survey eight diverse taxa were systematically chosen from published studies without regard to prior expectations about rates. Two approaches showed that rates of molecular and morphological evolution may usually be coupled. First, correlations in the total number of changes accumulated in terminal taxa suggest that some mechanism alters the rates of both morphological and molecular evolution in concert. Second, node-density effects were removed statistically, and average corrected base-to-tip totals were compared among sister clades. Across all taxa 50 of 72 of these corrected contrasts support the hypothesis that rates of molecular and morphological evolution are correlated; this finding is highly significant by a binomial test. Furthermore, there were positive correlations between inferred molecular and morphological branch lengths in seven of eight cases, which is also significant. These branch length correlations are consistent with the rate correlations, and suggest that amounts of molecular and morphological evolution often are correlated also. This study supports the assumptions of several phylogenetic methods, and highlights a need for new inquiries into many aspects of both molecular and morphological evolution.
自从祖克坎德尔和鲍林（1962年、1965年）提出分子钟以来，许多研究似乎都支持了他们的预测，即分子进化速率和形态进化速率通常会脱钩。这些研究大多针对那些形态进化速率被认为先验地差异很大的分类群。在本次调查中，从已发表的研究中系统地挑选了八个不同的分类群，而不考虑对进化速率的先验预期。两种方法表明，分子进化速率和形态进化速率通常可能是耦合的。首先，终端分类群中积累的变化总数的相关性表明，某种机制会协同改变形态进化速率和分子进化速率。其次，通过统计学方法消除节点密度效应，并比较姐妹分支类群之间平均校正后的碱基到末端的总数。在所有分类群中，72个经校正的对比中有50个支持分子进化速率和形态进化速率相关的假设；通过二项式检验，这一发现具有高度显著性。此外，在八个案例中的七个案例中，推断的分子分支长度和形态分支长度之间存在正相关，这也具有显著性。这些分支长度的相关性与速率相关性一致，并表明分子进化量和形态进化量通常也相关。本研究支持了几种系统发育方法的假设，并强调有必要对分子进化和形态进化的许多方面进行新的探究。
