Maddison Wayne P
Department of Zoology, Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z4.
Evolution. 2006 Aug;60(8):1743-6.
Studies of character evolution often assume that a phylogeny's shape is determined independently of the characters, which then evolve as mere passengers along the tree's branches. However, if the characters help shape the tree, but this is not considered, biased inferences can result. Simulations of asymmetrical speciation (i.e., one character state conferring a higher rate of speciation than another) result in data that are interpreted to show a higher rate of change toward the diversification-enhancing state, even though the rates to and from this state were in fact equal. Conversely, simulations of asymmetrical character change yield data that could be misinterpreted as showing asymmetrical rates of speciation. Studies of biased diversification and biased character change need to be unified by joint models and estimation methods, although how successfully the two processes can be teased apart remains to be seen.
性状演化的研究通常假定系统发育树的形态是独立于性状而确定的，而后性状仅仅作为沿着树的分支的“乘客”而演化。然而，如果性状有助于塑造系统发育树，但却未被考虑在内，就可能导致有偏差的推断。不对称物种形成（即一种性状状态赋予比另一种更高的物种形成速率）的模拟产生的数据会被解释为显示出朝着促进多样化状态的更高变化速率，尽管进出该状态的速率实际上是相等的。相反，不对称性状变化的模拟产生的数据可能会被误解为显示出不对称的物种形成速率。尽管这两个过程能在多大程度上被区分开来还有待观察，但有偏差的多样化和有偏差的性状变化的研究需要通过联合模型和估计方法来统一。
