Cuthill Jennifer F Hoyal, Braddy Simon J, Donoghue Philip C J
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK.
Cladistics. 2010 Feb;26(1):98-102. doi: 10.1111/j.1096-0031.2009.00270.x. Epub 2009 Jul 29.
To identify a biological signal in the distribution of homoplasy, it is first necessary to isolate non-biological factors affecting its measurement. The number of states per character in a phylogenetic data matrix may indicate evolutionary flexibility and, consequently, the likelihood of recurrent evolution. However, we show here that the number of states per character limits the maximum number of steps that may be inferred using parsimony. A formula is provided for the maximum number of steps that may be taken by a character with a given number of states and taxa. We show that as more character states are included the maximum proportion of steps that can be attributed to homoplasy falls, and the greatest amount of homoplasy measurable with the consistency index declines. © The Willi Hennig Society 2009.
为了在同塑性分布中识别生物信号，首先有必要分离影响其测量的非生物因素。系统发育数据矩阵中每个性状的状态数可能表明进化灵活性，进而表明反复进化的可能性。然而，我们在此表明，每个性状的状态数限制了使用简约法推断的最大步数。本文提供了一个公式，用于计算具有给定状态数和分类单元数的性状可能采取的最大步数。我们表明，随着包含的性状状态增多，可归因于同塑性的最大步数比例下降，并且用一致性指数可测量的最大同塑性量也下降。© 威利·亨尼希协会2009年。
