Data from: Stable coexistence of genetically divergent Atlantic cod ecotypes at multiple spatial scales

Coexistence in the same habitat of closely related yet genetically different populations is a phenomenon that challenges our understanding of local population structure and adaptation. Identifying the underlying mechanisms for such coexistence can yield new insight into adaptive evolution, diversification, and the potential for organisms to adapt and persist in response to a changing environment. Recent studies have documented cryptic, sympatric populations of Atlantic cod (Gadus morhua) in coastal areas. We analyzed genetic origin of 6483 individual cod sampled annually over 14 years from 125 locations along the Norwegian Skagerrak coast and document stable coexistence of two genetically divergent Atlantic cod ecotypes throughout the study area and study period. A ‘fjord’ ecotype dominated in numbers deep inside fjords while a 'North Sea' ecotype was the only type found in offshore North Sea. Both ecotypes coexisted in similar proportions throughout coastal habitats at all spatial scales. The size-at-age of the North Sea ecotype on average exceeded that of the fjord ecotype by 20% in length and 80% in weight across all habitats. Different growth and size among individuals of the two types might be one of several ecologically significant variables that allow for stable coexistence of closely related populations within the same habitat. Management plans, biodiversity initiatives, and other mitigation strategies that do not account for the mixture of species ecotypes are unlikely to meet objectives related to the sustainability of fish and fisheries.

亲缘关系紧密但遗传背景迥异的种群共存于同一栖息环境，这一现象对我们理解局域种群结构与适应性演化构成了挑战。阐明此类共存现象的内在机制，可为适应性演化、物种分化，以及生物响应环境变化实现适应与存续的相关研究提供全新视角。近期研究已在沿岸海域记录到大西洋鳕鱼（Gadus morhua）的隐蔽同域种群。本研究对挪威斯卡格拉克沿岸125个采样点、14年间逐年采集的6483尾大西洋鳕鱼个体开展遗传溯源分析，证实整个研究区域与研究周期内，两种遗传分化显著的大西洋鳕鱼生态型（ecotype）始终稳定共存。‘峡湾生态型’在峡湾深部的个体数量占据优势，而‘北海生态型’则是近海北海海域唯一被记录到的生态型。在所有空间尺度的沿岸栖息环境中，两种生态型均以相近的占比共存。在所有栖息环境中，北海生态型的平均年龄体型均优于峡湾生态型：体长超出20%，体重超出80%。两种生态型个体间的生长与体型差异，可能是促使亲缘关系紧密的种群在同一栖息环境中稳定共存的若干关键生态变量之一。若未考虑物种生态型的混合分布，现有管理计划、生物多样性保护举措及其他缓解策略，均难以达成鱼类与渔业可持续性相关的目标。