Due to the dearth of molecular markers variable enough to distinguish species of black corals, species delimitation in Antipatharia is still mainly based on morphological traits. One of the few markers available, the internal transcribed spacer (ITS) region located in ribosomal DNA, has already been used several times to infer phylogenetic relationships among antipatharians. However, this region was never considered in population-scale studies of shallow-water black corals till now. Here, we sampled two phenotypic variants of 41 specimens of the shallow-water antipatharian Stichopathes cf. maldivensis along the SW of Madagascar. The sampling area represents 200 km of shore and encompasses the runoffs of three rivers. We used direct sequencing to determine the main ITS1 types present in the genomes of the collected specimens and retrieved sequences from GenBank for Indonesian specimens. Then, we constructed a haploweb to visualize possible species boundaries using the criterion of mutual allelic exclusivity. With this method, we confirm that the previously described phenotypic variants belong to a single species that apparently extends from Indonesia to Madagascar. Likewise, the three rivers that pour freshwater in southwestern Madagascar do not appear to act as a barrier for the larval dispersal of this species. This study highlights the usefulness of ITS markers within antipatharians at both species and population levels.

由于缺乏足以区分黑珊瑚物种的分子标记物，因此Antipatharia中的物种划界仍然主要基于形态特征。少数可用的标记之一是位于核糖体DNA中的内部转录间隔区（ITS），已被多次用于推断抗病者之间的系统发育关系。但是，到目前为止，在浅水黑珊瑚的人口规模研究中从未考虑过该区域。在这里，我们抽样了41个浅水抗病性Stichopathes cf标本的表型变异。马尔代夫马达加斯加西南部。采样区域代表了200公里的海岸，涵盖了三条河流的径流。我们使用直接测序来确定收集标本的基因组中存在的主要ITS1类型，并从GenBank中检索印度尼西亚标本的序列。然后，我们构建了一个单倍网，以相互等位基因互斥的标准可视化可能的物种边界。通过这种方法，我们证实了先前描述的表型变异属于一个明显从印度尼西亚延伸到马达加斯加的物种。同样，在马达加斯加西南部倒入淡水的三条河似乎没有成为该物种幼虫传播的障碍。这项研究强调了ITS标记物在物种和种群水平的抗病者体内的有用性。