Agnarsson Ingi, Miller Jeremy A
Institute of Biology, Scientific Research Centre of the Slovenian Academy of Sciences and Arts, Novi trg 2, PO Box 306, SI-1001 Ljubljana, Slovenia.
Department of Biology, University of Akron, Akron, OH 44325-3908, USA.
Cladistics. 2008 Dec;24(6):1032-1038. doi: 10.1111/j.1096-0031.2008.00229.x. Epub 2008 Aug 28.
When parsimony ancestral character reconstruction is ambiguous, it is often resolved in favour of the more complex character state. Hence, secondary loss (secondary "absence") of a complex feature is favoured over parallel gains of that feature as this preserves the stronger hypothesis of homology. We believe that such asymmetry in character state complexity is important information for understanding character evolution in general. However, we here point out an inappropriate link that is commonly made between this approach and the accelerated transformation (ACCTRAN) algorithm. In ACCTRAN, changes are assigned along branches of a phylogenetic tree as close to the root as possible. This has been taken to imply that ACCTRAN will minimize hypotheses of parallel origins of complex traits and thus that ACCTRAN is philosophically better justified than the alternatives, such as delayed transformation (DELTRAN), where changes are assigned along branches as close to the tips as possible. We provide simple examples to show that such views are mistaken and that neither ACCTRAN nor DELTRAN consistently minimize parallel gain of complex traits. We therefore do not see theoretical grounds for favouring the popular ACCTRAN algorithm. © The Willi Hennig Society 2008.
当简约法进行的祖先性状重建结果不明确时，通常会倾向于更复杂的性状状态来解决。因此，复杂特征的次生丢失（次生“缺失”）比该特征的平行获得更受青睐，因为这样能保留更强的同源性假设。我们认为，性状状态复杂性方面的这种不对称性是理解一般性状进化的重要信息。然而，我们在此指出这种方法与加速变换（ACCTRAN）算法之间通常存在的一种不恰当联系。在ACCTRAN中，变化沿着系统发育树的分支尽可能靠近根部进行分配。这被认为意味着ACCTRAN将使复杂性状平行起源的假设最小化，因此从理论上讲，ACCTRAN比其他方法（如延迟变换（DELTRAN），其中变化沿着分支尽可能靠近末梢进行分配）更有依据。我们提供了简单的例子来说明这种观点是错误的，而且ACCTRAN和DELTRAN都不能始终如一地使复杂性状的平行获得最小化。因此，我们认为没有理论依据支持流行的ACCTRAN算法。© 威利·亨尼希协会2008年。
