Feuda Roberto, Smith Andrew B
Division of Biology and Biological Engineering, California Institute of Technology Pasadena, California, United States of America.
Department of Earth Sciences, The Natural History Museum, London, United Kingdom.
PLoS One. 2015 May 8;10(5):e0123331. doi: 10.1371/journal.pone.0123331. eCollection 2015.
Relationships within the class Asteroidea have remained controversial for almost 100 years and, despite many attempts to resolve this problem using molecular data, no consensus has yet emerged. Using two nuclear genes and a taxon sampling covering the major asteroid clades we show that non-phylogenetic signal created by three factors--Long Branch Attraction, compositional heterogeneity and the use of poorly fitting models of evolution--have confounded accurate estimation of phylogenetic relationships. To overcome the effect of this non-phylogenetic signal we analyse the data using non-homogeneous models, site stripping and the creation of subpartitions aimed to reduce or amplify the systematic error, and calculate Bayes Factor support for a selection of previously suggested topological arrangements of asteroid orders. We show that most of the previous alternative hypotheses are not supported in the most reliable data partitions, including the previously suggested placement of either Forcipulatida or Paxillosida as sister group to the other major branches. The best-supported solution places Velatida as the sister group to other asteroids, and the implications of this finding for the morphological evolution of asteroids are presented.
在近100年里，海星纲内部的关系一直存在争议，尽管人们多次尝试利用分子数据解决这一问题，但尚未达成共识。我们使用两个核基因，并对涵盖主要海星分支的分类群进行采样，结果表明，由长枝吸引、成分异质性和使用拟合不佳的进化模型这三个因素产生的非系统发育信号，混淆了系统发育关系的准确估计。为了克服这种非系统发育信号的影响，我们使用非齐次模型、位点剥离以及创建旨在减少或放大系统误差的子分区来分析数据，并计算贝叶斯因子支持度，以选择先前提出的海星目拓扑排列。我们表明，在最可靠的数据分区中，大多数先前的替代假设都不成立，包括先前提出的将钳棘目或栉蛇尾目作为其他主要分支的姐妹群的位置。得到最佳支持的解决方案是将帆海星目作为其他海星的姐妹群，并阐述了这一发现对海星形态进化的影响。
