Lázaro Eva M, Sluys Ronald, Pala Maria, Stocchino Giacinta Angela, Baguñà Jaume, Riutort Marta
Institut de Recerca de la Biodiversitat i, Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain.
Mol Phylogenet Evol. 2009 Sep;52(3):835-45. doi: 10.1016/j.ympev.2009.04.022. Epub 2009 May 10.
Planarians of the genus Dugesia have a worldwide distribution with high species diversity in the Mediterranean area. In this area, populations with a triploid karyotype that reproduce by fissiparity are exceptionally frequent, outnumbering the sexual populations. This situation poses interesting questions, such as the age of these asexual lineages, whether they all belong to the same species or whether the triploidization event is recurrent, and what factors (climatic, geographical, historical...) explain the prevalence of these asexual forms. However, asexual populations cannot be assigned to a species due to the lack of copulatory apparatus--the main structure used in species identification. In this study, we have developed a DNA barcoding method, based on COI and ITS-1 sequences, which allows the assignment of the fissiparous forms to sexual species. At the same time, phylogenetic analysis from species of the western Mediterranean have unveiled the presence of species with highly differentiated populations alongside species with a wide distribution and almost no genetic variation. The roles of habitat instability, dispersal capacity and human activities are briefly discussed.
真涡虫属的涡虫分布于全球，在地中海地区物种多样性很高。在该地区，具有三倍体核型且通过分裂生殖进行繁殖的种群异常常见，数量超过有性生殖种群。这种情况引发了一些有趣的问题，比如这些无性系的年龄、它们是否都属于同一物种，或者三倍体化事件是否反复发生，以及哪些因素（气候、地理、历史……）解释了这些无性形态的盛行。然而，由于缺乏交配器官——物种鉴定中使用的主要结构，无性生殖种群无法被归为一个物种。在本研究中，我们基于细胞色素氧化酶亚基I（COI）和内转录间隔区1（ITS-1）序列开发了一种DNA条形码方法，该方法可将分裂生殖形式归为有性生殖物种。同时，对西地中海地区物种的系统发育分析揭示了存在种群高度分化的物种以及分布广泛且几乎没有遗传变异的物种。文中还简要讨论了栖息地不稳定性、扩散能力和人类活动的作用。
