Molecular species delimitation of reef-building coral genera, <i>Porites</i> and <i>Turbinaria</i> (Anthozoa: Scleractinia), from the intertidal fringing reefs of Gulf of Kutch, India reveals unrecognized diversity

Knowledge of extant biodiversity with accurate species boundaries is one of the crucial prerequisites for guiding conservation priorities in the face of global climate change. DNA taxonomy promises to provide a rapid and reliable tool for species delimitation of morphologically challenging taxa, such as reef-building corals. Despite harbouring diverse coral assemblages, molecular studies of hard corals occurring in the seas around India are lacking. The Gulf of Kutch (GoK), located in the north-western part of India, is one such region. Information on coral species inhabiting this unique ecosystem is limited to morphology, which is often highly variable and phenotypically plastic, obscuring species boundaries. Here, we present the first exploration of molecular divergence of hard corals of the GoK in order to identify evolutionarily distinct lineages. Nuclear ribosomal ITS and mitochondrial <i>COI</i> markers were sequenced for samples of dominant genera, <i>Porites</i> and <i>Turbinaria</i> for phylogenetic comparisons with available data from other ecosystems of the world. Five molecular species delimitation methods were applied to the datasets and their performance was evaluated. Our analyses clearly suggest the occurrence of unique genotypes of both these genera in the GoK, unequivocally discerned by all the five methods as well as microskeletal features. This first integrative assessment provides implications for the phylogeny of these genera and identifies previously unrecognized scleractinian species hidden in the GoK ecoregion.准确界定物种边界的现存生物多样性认知，是全球气候变化背景下制定保护优先级的核心前提之一。DNA分类学（DNA taxonomy）可为形态鉴定存在挑战的类群（如造礁珊瑚）提供快速可靠的物种界定工具。尽管印度周边海域拥有丰富的珊瑚群落，但针对该区域石珊瑚的分子研究仍较为匮乏，位于印度西北部的库奇湾（Gulf of Kutch, GoK）正是此类研究空白区域之一。目前关于该独特生态系统内珊瑚物种的信息仅局限于形态学数据，而形态特征往往具有高度变异性与表型可塑性，极易模糊物种边界。本研究首次对库奇湾的石珊瑚开展分子分化分析，以鉴定演化上独立的支系：我们对该区域优势属——<i>Porites</i>属与<i>Turbinaria</i>属的样本，进行了核糖体DNA内转录间隔区（ITS）与线粒体细胞色素C氧化酶亚基I（<i>COI</i>）的测序，用于与全球其他生态系统的已有数据开展系统发育比较；同时针对数据集应用了五种分子物种界定方法，并评估了各方法的表现。分析结果清晰显示，库奇湾内这两个属均存在独特的基因型，且五种分子方法与微骨骼特征均可明确区分此类基因型。这项首次综合性研究不仅为这两个属的系统发育研究提供了新的科学启示，还揭示了库奇湾生态区内此前未被认知的石珊瑚物种。