Distribution and phenotypic variability of the Mediterranean gorgonian <i>Paramuricea macrospina</i> (Cnidaria: Octocorallia)

The genus <i>Paramuricea</i> is present in the Mediterranean Sea with two species, <i>P. clavata</i> and <i>P. macrospina</i>. These species have similar bathymetric distributions and can live in sympatry. <i>P. macrospina</i> shows morphological plasticity leading sometimes to an erroneous classification as <i>P. clavata</i>. Studying four ambiguous morphotypes of <i>P. macrospina</i> collected in different localities of the Mediterranean Sea, we provide new insights on both the taxonomy and the distribution of this species. Our analyses reveal high morphological plasticity within the sampled colonies, which in two cases were characterised by a peculiar pigmentation and a morphological pattern resembling that of <i>P. clavata</i>. After having confirmed the genetic identity of the samples, we tested the validity of traditional taxonomic characters, and found that the most reliable character to discriminate between <i>P. macrospina</i> and <i>P. clavata</i> is the number of rows of spindles in the collaret of the polyps. All other features are highly variable and therefore do not allow a correct identification. The bathymetric and geographic distribution of <i>P. macrospina</i> is here updated, showing, with the exception of the south-eastern side, broad preference in the whole basin. Moreover, further studies are needed to investigate the gene flow among and within the Mediterranean populations of <i>P. macrospina</i> and to assess whether the morphological plasticity is driven by adaptive genetic processes of populations exposed to different environmental, climatic and bathymetric conditions.地中海海域分布有紫柳珊瑚属（*Paramuricea*）的两个物种，即棒状紫柳珊瑚（*P. clavata*）与大棘紫柳珊瑚（*P. macrospina*）。二者的水深分布特征相近，且可同域共存。大棘紫柳珊瑚（*P. macrospina*）具有显著的表型可塑性，偶尔会被误鉴定为棒状紫柳珊瑚（*P. clavata*）。本研究采集了地中海不同海域的4份大棘紫柳珊瑚的模糊形态型样本，为该物种的分类学与分布格局研究提供了新的视角。分析结果显示，采样的珊瑚群体内部存在高度的表型可塑性，其中2份样本具有独特的色素沉着特征，且形态模式与棒状紫柳珊瑚相似。在确认样本的遗传身份后，我们对传统分类学特征的有效性进行了检验，结果表明：区分大棘紫柳珊瑚与棒状紫柳珊瑚最可靠的特征为珊瑚虫领部的骨针列数；其余所有特征均具有较高的变异性，无法实现准确的物种鉴定。本研究更新了大棘紫柳珊瑚的水深与地理分布数据，结果显示该物种在整个地中海盆地广泛分布，仅东南海域除外。此外，未来仍需开展进一步研究，以探明大棘紫柳珊瑚地中海种群内部及种群间的基因流情况，并评估其表型可塑性是否由暴露于不同环境、气候与水深条件的种群所经历的适应性遗传过程所驱动。