ABSTRACT: The order Polycladida comprises a highly diverse and cosmopolitan group of marine turbellarian flatworms. Owing to the great morphological diversity and the absence of a molecular phylogeny, the classification of this group has always been controversial. Here we seek to add resolution by reporting the results of molecular phylogenetic analysis based on sequences of the 28S ribosomal RNA gene, thus providing a framework for understanding relationships and the evolution of characters within the group. The phylogeny provides strong support for 10 and 7 distinct families within the suborders Acotylea and Cotylea, respectively. In addition, an analysis based on the mitochondrial gene sequences (cytochrome c-oxidase subunit I) reveals further details of the relationships within Acotylea, which were classified by morphological analysis, but not by 28S rRNA sequence-based analyses. These analyses also showed that several species corresponded to previously described genera based on morphological features and character combinations. We conclude that a classification of genera in Acotylea and Cotylea based on molecular phylogeny reflects the morphological diversity of these polyclad flatworms.

中文翻译：

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日本海洋turbularian扁虫（Platyhelminthes，Polycladida）的分类学和系统学的分子框架

摘要：Polycladida目包括高度多样化和国际化的海洋turbularian扁虫群。由于巨大的形态多样性和分子系统发育的缺乏，该组的分类一直存在争议。在这里，我们试图通过报告基于28S核糖体RNA基因序列的分子系统发育分析的结果来提高分辨率，从而为理解群体中的亲缘关系和进化提供框架。系统发育分别为子亚目和子叶亚目中的10个和7个不同的家族提供了有力的支持。此外，基于线粒体基因序列（细胞色素c-氧化酶亚基I）揭示了Acotylea内部关系的更多细节，这些细节通过形态学分析进行了分类，但没有通过基于28S rRNA序列的分析进行分类。这些分析还显示，根据形态特征和特征组合，几种物种对应于先前描述的属。我们得出的结论是，基于分子系统发育的子叶和子叶属的分类反映了这些多翅扁平虫的形态多样性。