Butler Marguerite A, Losos Jonathan B
Department of Biology, Campus Box 1137, Washington University, Saint Louis, Missouri, 63130.
Evolution. 1997 Oct;51(5):1623-1635. doi: 10.1111/j.1558-5646.1997.tb01485.x.
Although a large body of work investigating tests of correlated evolution of two continuous characters exists, hypotheses such as character displacement are really tests of whether substantial evolutionary change has occurred on a particular branch or branches of the phylogenetic tree. In this study, we present a methodology for testing such a hypothesis using ancestral character state reconstruction and simulation. Furthermore, we suggest how to investigate the robustness of the hypothesis test by varying the reconstruction methods or simulation parameters. As a case study, we tested a hypothesis of character displacement in body size of Caribbean Anolis lizards. We compared squared-change, weighted squared-change, and linear parsimony reconstruction methods, gradual Brownian motion and speciational models of evolution, and several resolution methods for linear parsimony. We used ancestor reconstruction methods to infer the amount of body size evolution, and tested whether evolutionary change in body size was greater on branches of the phylogenetic tree in which a transition from occupying a single-species island to a two-species island occurred. Simulations were used to generate null distributions of reconstructed body size change. The hypothesis of character displacement was tested using Wilcoxon Rank-Sums. When tested against simulated null distributions, all of the reconstruction methods resulted in more significant P-values than when standard statistical tables were used. These results confirm that P-values for tests using ancestor reconstruction methods should be assessed via simulation rather than from standard statistical tables. Linear parsimony can produce an infinite number of most parsimonious reconstructions in continuous characters. We present an example of assessing the robustness of our statistical test by exploring the sample space of possible resolutions. We compare ACCTRAN and DELTRAN resolutions of ambiguous character reconstructions in linear parsimony to the most and least conservative resolutions for our particular hypothesis.
尽管存在大量研究两个连续性状相关进化测试的工作，但诸如性状替换等假设实际上是对系统发育树的特定一个或多个分支上是否发生了实质性进化变化的测试。在本研究中，我们提出了一种使用祖先性状状态重建和模拟来检验此类假设的方法。此外，我们建议如何通过改变重建方法或模拟参数来研究假设检验的稳健性。作为一个案例研究，我们检验了加勒比安乐蜥体型性状替换的假设。我们比较了平方变化、加权平方变化和线性简约重建方法、渐进布朗运动和物种形成进化模型，以及线性简约的几种分辨率方法。我们使用祖先重建方法来推断体型进化的量，并检验在系统发育树中从占据单物种岛屿过渡到双物种岛屿的分支上，体型的进化变化是否更大。模拟用于生成重建体型变化的零分布。使用威尔科克森秩和检验来检验性状替换的假设。当与模拟的零分布进行比较时，所有重建方法得出的P值都比使用标准统计表时更显著。这些结果证实，使用祖先重建方法进行检验的P值应通过模拟而非标准统计表来评估。线性简约在连续性状中可以产生无限数量的最简约重建。我们通过探索可能分辨率的样本空间，给出了一个评估我们统计检验稳健性的例子。我们将线性简约中模糊性状重建的ACCTRAN和DELTRAN分辨率与我们特定假设的最保守和最不保守分辨率进行比较。
