Dpt. de Genètica, Microbiologia i Estadística, Facultat de Biologia, and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain.
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
Mol Phylogenet Evol. 2020 Feb;143:106496. doi: 10.1016/j.ympev.2019.05.010. Epub 2019 May 28.
The keystone of planarian taxonomy traditionally has been the anatomy of the copulatory apparatus. However, many planarian species comprise asexual fissiparous populations, with the fissiparous animals not developing a copulatory apparatus, thus precluding their morphological identification. Incorporation of molecular data into planarian systematics has been of great value, not only in the identification of fissiparous individuals but also as an additional source of information for determining species boundaries. Nevertheless, the discrepancy between morphological and molecular data has highlighted the need for extra sources of taxonomic information. Moreover, a recent study has pointed out that fissiparous reproduction may lead to high levels of intraindividual genetic diversity in planarians, which may mislead molecular analyses. In the present study we aim to test a new up-to-date integrative taxonomic procedure for planarians, including intraindividual genetic data and additional sources of taxonomic information, besides morphology and DNA, using Dugesia subtentaculata sensu lato as a model organism, a species with an intricate taxonomic history. First, we used three different methods for molecular species delimitation on single locus datasets, both with and without intraindividual information, for formulating Primary Species Hypotheses (PSHs). Subsequently, Secondary Species Hypotheses (SSHs) were formulated on the basis of three types of information: (1) a coalescent-based species delimitation method applied to multilocus data, (2) morphology of the copulatory apparatus, and (3) karyological metrics. This resulted in the delimitation of four morphologically cryptic species within the nominal species D. subtentaculata. Our results provide evidence that the analysis of intraindividual genetic data is essential for properly developing PSHs in planarians. Our study reveals also that karyological differentiation, rather than morphological differentiation, may play an important role in speciation processes in planarians, thus suggesting that the currently known diversity of the group could be highly underestimated.
传统上，扁形动物分类学的基石一直是交配器官的解剖结构。然而，许多扁形动物包含无性裂体生殖种群，裂体生殖动物不发育交配器官，因此无法对其进行形态鉴定。将分子数据纳入扁形动物系统学具有重要价值，不仅可以识别裂体生殖个体，还可以为确定物种界限提供额外的信息来源。然而，形态和分子数据之间的差异突出表明需要额外的分类学信息来源。此外，最近的一项研究指出，裂体生殖可能导致扁形动物个体内遗传多样性水平较高，这可能会误导分子分析。在本研究中，我们旨在测试一种新的、最新的扁形动物综合分类程序，该程序包括个体内遗传数据和除形态和 DNA 之外的其他分类学信息来源，以 Dugesiasubtentaculata sensu lato 为模型生物，该物种具有复杂的分类历史。首先，我们使用三种不同的方法在单基因座数据集上进行分子物种界限界定，包括有和没有个体内信息，以制定主要物种假设 (PSH)。随后，根据三种类型的信息制定次要物种假设 (SSH)：(1) 应用于多基因座数据的基于合并的物种界限界定方法，(2) 交配器官的形态，和 (3) 染色体计量学。这导致在名义物种 D.subtentaculata 内界定了四个形态上隐蔽的物种。我们的结果提供了证据，表明分析个体内遗传数据对于正确制定扁形动物的 PSH 至关重要。我们的研究还表明，染色体分化而不是形态分化可能在扁形动物的物种形成过程中发挥重要作用，这表明该组目前已知的多样性可能被严重低估。
