Assessing the distribution of species in natural environments is essential for their use in environmental surveys. Here, we investigate the distribution of three pseudo-cryptic species formerly lumped in the morphospecies (Cushman, 1926) commonly found on estuarine mudflats along the European coasts: Schultze, 1854 (T1), Haynes, 1973 (T2) and Zheng, 1978 (T6). We studied their distribution at 51 sites located in seven estuaries of the French North Atlantic coast (Elorn, Aulne, Odet, Crac'h, Auray, Vilaine, Vie), using both morphological and molecular identification methods. was detected by both approaches at most of the stations. While was frequently identified by the morphological method but not detected with metabarcoding, the presence of in the eDNA data often contrasted with its absence in the morphological analysis. The absence of in eDNA of sites where it was identified morphologically could be the consequence of its relative scarcity, and eventually a patchy distribution. Concerning we hypothesise that these contradictory results can be explained by the supposedly invasive character of this species. Despite the widespread presence of genetic material (including adults, juveniles and propagules), a mature population has not yet fully developed everywhere. The seven investigated estuaries seem to represent different stages of replacement of the autochthonous species and by . Our study demonstrates that the combination of visual observations and molecular approaches is ideal for monitoring the progressive spreading of exotic species.

中文翻译：

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使用形态学和元条形码方法揭示法国大西洋海岸河口三种氨物种（有孔虫、根茎）的分布

评估自然环境中物种的分布对于将其用于环境调查至关重要。在这里，我们调查了欧洲沿岸河口泥滩上常见的形态种（Cushman，1926）中的三种伪隐秘物种的分布：Schultze，1854（T1）、Haynes，1973（T2）和Zheng，1978（ T6）。我们使用形态学和分子鉴定方法研究了它们在法国北大西洋海岸七个河口（Elorn、Aulne、Odet、Crac'h、Auray、Vilaine、Vie）的 51 个地点的分布。大多数站点都通过两种方法检测到。虽然经常通过形态学方法识别但未通过元条形码检测到，但 eDNA 数据中的存在通常与其在形态学分析中的缺失形成对比。 eDNA 中缺乏形态学鉴定位点可能是其相对稀缺的结果，并最终导致分布不均匀。关于这一点，我们假设这些矛盾的结果可以用该物种的入侵特征来解释。尽管遗传物质广泛存在（包括成虫、幼虫和繁殖体），但成熟种群尚未在各地完全发育。所调查的七个河口似乎代表了本地物种和被替代的不同阶段。我们的研究表明，视觉观察和分子方法的结合是监测外来物种逐渐扩散的理想选择。