School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland 1142, New Zealand.
Mol Phylogenet Evol. 2011 Nov;61(2):351-62. doi: 10.1016/j.ympev.2011.07.005. Epub 2011 Jul 21.
Phylogenetic relationships within the bryozoan order Cheilostomata are currently uncertain, with many morphological hypotheses proposed but scarcely tested by independent means of molecular analysis. This research uses DNA sequence data across five loci of both mitochondrial and nuclear origin from 91 species of cheilostome Bryozoa (34 species newly sequenced). This vastly improved the taxonomic coverage and number of loci used in a molecular analysis of this order and allowed a more in-depth look into the evolutionary history of Cheilostomata. Maximum likelihood and Bayesian analyses of individual loci were carried out along with a partitioned multi-locus approach, plus a range of topology tests based on morphological hypotheses. Together, these provide a comprehensive set of phylogenetic analyses of the order Cheilostomata. From these results inferences are made about the evolutionary history of this order and proposed morphological hypotheses are discussed in light of the independent evidence gained from the molecular data. Infraorder Ascophorina was demonstrated to be non-monophyletic, and there appears to be multiple origins of the ascus and associated structures involved in lophophore extension. This was further supported by the lack of monophyly within each of the four ascophoran grades (acanthostegomorph/spinocystal, hippothoomorph/gymnocystal, umbonulomorph/umbonuloid, lepraliomorph/lepralioid) defined by frontal-shield morphology. Chorizopora, currently classified in the ascophoran grade Hippothoomorpha, is phylogenetically distinct from Hippothoidae, providing strong evidence for multiple origins of the gymnocystal frontal shield type. Further evidence is produced to support the morphological hypothesis of multiple umbonuloid origins of lepralioid frontal shields, using a step-wise set of topological hypothesis tests combined with examination of multi-locus phylogenies.
层孔虫目的系统发育关系目前还不确定，虽然提出了许多形态假说，但很少有通过独立的分子分析方法进行检验。本研究利用了来自 91 种层孔虫（34 种为新测序物种）的线粒体和核起源的五个基因座的 DNA 序列数据。这极大地提高了分子分析该目的分类覆盖率和基因座数量，并更深入地研究了层孔虫的进化历史。对单个基因座进行了最大似然和贝叶斯分析，并采用了分区多基因座方法，以及一系列基于形态假说的拓扑测试。这些方法共同提供了层孔虫目的综合系统发育分析。根据这些结果，对该目的进化历史进行了推断，并根据分子数据获得的独立证据讨论了所提出的形态假说。ascophorina 亚目被证明不是单系的，而且似乎存在多种原腔动物和相关结构的起源，这些结构涉及到纤毛的延伸。这进一步得到了每个 ascophoran 等级（acanthostegomorph/spinocystal、hippothoomorph/gymnocystal、umbonulomorph/umbonuloid、lepraliomorph/lepralioid）内缺乏单系性的支持，这些等级是根据额盾形态定义的。Chorizopora 目前被归类为 ascophoran 等级的 Hippothoomorpha，在系统发育上与 Hippothoidae 不同，为 gymnocystal 额盾类型的多种起源提供了有力证据。通过使用一系列逐步的拓扑假设测试结合多基因座系统发育的检查，进一步提供了支持 lepralioid 额盾具有多种起源的形态假说的证据。
