Schultz Ted R, Cocroft Reginald B, Churchill Gary A
Department of Entomology, Comstock Hall, Cornell University, Ithaca, New York, 14853.
Section of Neurobiology and Behavior, Seeley G. Mudd Hall, Cornell University, Ithaca, New York, 14853.
Evolution. 1996 Apr;50(2):504-511. doi: 10.1111/j.1558-5646.1996.tb03863.x.
The problem of error in the phylogenetic reconstruction of ancestral character states is explored by developing the model of Frumhoff and Reeve (1994). Information about the evolutionary rate of change within a character is inferred from the distribution of its character states on a known phylogeny, and this information is used to impose confidence limits on the error associated with ancestral state inference. Ancestral state inference is found to be remarkably robust under the model assumptions for a wide range of parameter values; however, the probability of error increases when the number of species within a clade is small and/or state-transition probabilities are strongly skewed in favor of the non-ancestral state. The rationale for expecting such a skew, a hypothesis of parallelism, is shown to rely on assumptions of low rates of change in at least two phylogenetically inherited characters: the tendency to occupy a particular ecological niche and the tendency to respond in a particular way to selection. A means for judging the relative likelihoods of parallelism vs. straightforward homology as explanations for a given character-state distribution is suggested. General problems with the model are discussed, as are methods for making it more realistic.
通过发展弗鲁姆霍夫和里夫（1994年）的模型，探讨了祖先性状状态系统发育重建中的误差问题。从一个性状在已知系统发育树上的性状状态分布推断该性状内部的进化变化率信息，并利用此信息对与祖先状态推断相关的误差施加置信限。发现在广泛的参数值范围内，在模型假设下祖先状态推断非常稳健；然而，当一个分支内的物种数量较少和/或状态转换概率强烈偏向非祖先状态时，误差概率会增加。预期这种偏向的基本原理，即平行性假说，被证明依赖于至少两个系统发育遗传性状的低变化率假设：占据特定生态位的倾向和以特定方式对选择作出反应的倾向。提出了一种判断平行性与直接同源性作为给定性状状态分布解释的相对可能性的方法。讨论了该模型的一般问题以及使其更符合实际的方法。
