Intraspecific genetic admixture and the morphological diversification of an estuarine fish population complex

The North-east American Rainbow smelt (Osmerus mordax) is composed of two glacial races first identified through the spatial distribution of two distinct mtDNA lineages. Contemporary breeding populations of smelt in the St. Lawrence estuary comprise contrasting mixtures of both lineages, suggesting that the two races came into secondary contact in this estuary. The overall objective of this study was to assess the role of intraspecific genetic admixture in the morphological diversification of the estuarine rainbow smelt population complex. The morphology of mixed-ancestry populations varied as a function of the relative contribution of the two races to estuarine populations, supporting the hypothesis of genetic admixture. Populations comprising both ancestral mtDNA races did not exhibit intermediate morphologies relative to pure populations but rather exhibited many traits that exceeded the parental trait values, consistent with the hypothesis of transgressive segregation. Evidence for ...美洲东北彩虹胡瓜鱼（Osmerus mordax）由两个冰川支系种群构成，二者最初通过两种截然不同的线粒体DNA（mtDNA）谱系的空间分布特征得以鉴定。当前栖息于圣劳伦斯河口湾的胡瓜鱼繁殖种群，呈现出两类谱系的混合共存特征，表明这两个支系种群已在该河口湾发生次生接触。本研究的核心目标为评估种内遗传混杂在河口湾彩虹胡瓜鱼种群复合体形态多样化进程中所发挥的作用。研究结果显示，具有混合祖先背景的种群，其形态特征随两个支系种群对河口湾种群的相对贡献比例而发生变化，这一发现支持了遗传混杂相关假说。相较于纯种种群，同时携带两类祖先线粒体DNA谱系的种群并未呈现出中间过渡形态，反而表现出诸多超出亲本性状值的特征，这与超亲分离（transgressive segregation）假说相符。相关研究证据表明……