Ecological and biogeographic information for marine gastropods has lagged behind taxonomic, molecular and phylogenetic information, limiting understanding of evolutionary processes. We investigated niche separation and speciation in rapinine whelks that represent a rare deep estuarine penetration by muricid gastropods. We studied the genetic and ecological differentiation of four Indothais morphotypes, distributed along a salinity gradient in Brunei (Borneo, South East Asia). Our molecular analyses, based on three mitochondrial genes (COI, 12S rRNA and 16S rRNA) and one nuclear gene (28S rRNA), revealed three species having the following relationship [Indothais rufotincta (Tan & Sigurdsson, 1996), [I. javanica (Philippi, 1848), [I. gradata (Jonas, 1846)]]]. This pattern coincided with their salinity-related distributions, such that I. rufotincta occurred alone in the open coastal waters, and I. javanica and I. gradata extended into the upper estuary. This suggests speciation through divergent selection and local adaptation, specifically synapomorphic low salinity tolerance by I. javanica and I. gradata. The observed intertidal vertical separation where the species co-occur suggests competitive exclusion of the others by the most-recently evolved I. gradata. This species also showed greatest morphological and genetic variation, and unique niche expansion involving feeding on both hard surface and muddy sediment organisms. Our study presents a novel hypothesis for the speciation of these snails.

中文翻译：

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进化的河口入侵：婆罗洲 Indothais 蜗牛（Rapaninae，Muricidae）的分子分化和生态位分离

海洋腹足动物的生态和生物地理信息落后于分类、分子和系统发育信息，限制了对进化过程的理解。我们研究了代表鼠腹足类动物罕见的深河口穿透的 rapinine 螺的生态位分离和物种形成。我们研究了四种植物的遗传和生态分化印度人形态型，沿着文莱（婆罗洲，东南亚）的盐度梯度分布。我们的分子分析基于三个线粒体基因（COI、12S rRNA 和 16S rRNA）和一个核基因（28S rRNA），揭示了三个物种具有以下关系[红毛茛(Tan & Sigurdsson, 1996), [一、爪哇（菲利普，1848），[一、毕业数据（乔纳斯，1846 年）]]]。这种模式与它们与盐度相关的分布相吻合，因此I. rufotincta单独发生在开阔的沿海水域，并且一、爪哇和一、毕业数据延伸至河口上游。这表明通过不同的选择和局部适应进行物种形成，特别是通过一、爪哇和一、毕业数据. 观察到的潮间带垂直分离，其中物种共存表明最近进化的物种竞争排斥其他物种一、毕业数据. 该物种还表现出最大的形态和遗传变异，以及独特的生态位扩张，包括以坚硬的表面和泥泞的沉积生物为食。我们的研究为这些蜗牛的物种形成提出了一个新假设。