ABSTRACT

Species of Ulva Linnaeus are nearly impossible to identify using morpho-anatomy due to their simple thallus structure and phenotypic plasticity. The current solution to this problem is to sequence DNA from field-collected specimens and match these sequences to those available in public DNA databases. However, because type specimens of many species have not been sequenced, the accuracy of these identifications is highly doubtful. Ulva rigida C.Agardh is reported to be one of the most widespread and ecologically important Ulva species, but these records are based on either morpho-anatomy or, more recently, on DNA sequences. High-throughput sequencing (HTS) was performed on the lectotype specimen of U. rigida from Cádiz, Spain to determine the correct application of the name. The analysis yielded its complete plastid genome. rbcL, tufA and ITS sequences from the lectotype specimen differed at the species level from all U. rigida sequences deposited in public databases. Instead, the lectotype sequences of U. rigida were identical or very similar to sequences identified as U. rotundata Bliding (referred to by some as U. pseudorotundata Cormaci, G.Furnari & Alongi) from Ireland and Portugal, but not to the holotype of U. rotundata from Italy, which was identical to U. lactuca L. HTS of the lectotype of U. lacinulata (Kützing) Wittrock from Lesina, Croatia, a species morphologically similar to U. rigida with macroscopic marginal teeth, also yielded a complete plastid genome, with sequences identical or highly similar to GenBank U. armoricana Dion, Reviers & Coat, U. ‘laetevirens’, U. ‘rigida’ and U. scandinavica Bliding. Since U. lacinulata is the oldest validly published name, it is the correct one to apply to the globally distributed species that was previously but incorrectly known as U. rigida. Based on this genetic evidence, U. rigida is restricted to European waters and confirmed by DNA sequences from Ireland, Portugal and Spain. This analysis shows that many barcode species identifications and taxonomic conclusions in the genus Ulva are incorrect.

摘要

由于其简单的菌体结构和表型可塑性，使用形态解剖学几乎不可能识别石莼属的物种。目前解决这个问题的方法是对现场采集的样本中的 DNA 进行测序，并将这些序列与公共 DNA 数据库中可用的序列进行匹配。然而，由于许多物种的模式标本尚未测序，这些鉴定的准确性非常值得怀疑。据报道，石莼属C.Agardh 是最广泛和生态上最重要的石莼物种之一，但这些记录要么基于形态解剖学，要么基于最近的 DNA 序列。对U.rigida的选型标本进行高通量测序 (HTS)来自西班牙加的斯，以确定该名称的正确应用。分析产生了其完整的质体基因组。来自选型标本的rbc L、tuf A 和 ITS 序列在物种水平上与公共数据库中保存的所有U.rigida序列不同。相反，U.rigida 的选型序列与来自爱尔兰和葡萄牙的被鉴定为U. rotundata Bliding（一些人称为U. pseudorotundata Cormaci、G.Furnari 和 Alongi）的序列相同或非常相似，但与U. rotundata来自意大利，与U. lacinulata选型的U. lactuca L. HTS相同(Kützing) 来自克罗地亚 Lesina 的 Wittrock 是一种在形态上与具有肉眼边缘牙齿的 U.rigida 相似的物种，也产生了完整的质体基因组，其序列与 GenBank U. armouricana Dion, Reviers & Coat , U. ' laetevirens '，美国。' rigida ' 和U. scandinavica Bliding。由于U. lacinulata是最古老的有效出版名称，因此它是正确的名称，适用于以前但错误地称为U. rida的全球分布物种。基于这一遗传证据，U.rigida仅限于欧洲水域，并由爱尔兰、葡萄牙和西班牙的 DNA 序列证实。该分析表明，石莼属中的许多条形码物种鉴定和分类学结论是不正确的。