Data from: Metapopulation patterns of additive and nonadditive genetic variance in the sea bass (Dicentrarchus labrax)

Describing and explaining the geographic within-species variation in phenotypes (“phenogeography”) in the sea over a species distribution range is central to our understanding of a variety of eco-evolutionary topics. However, phenogeographic studies that have a large potential to investigate adaptive variation are overcome by phylogeographic studies, still mainly focusing on neutral markers. How genotypic and phenotypic data could covary over large geographic scales remains poorly understood in marine species. We crossed 75 noninbred sires (five origins) and 26 dams (two origins; each side of a hybrid zone) in a factorial diallel cross in order to investigate geographic variation for early survival and sex ratio in the metapopulation of the European sea bass (Dicentrarchus labrax), a highly prized marine fish species. Full-sib families (N = 1,950) were produced and reared in a common environment. Parentage assignment of 7,200 individuals was performed with seven microsatellite markers. Generalized linear models showed significant additive effects for both traits and pleiotropy between traits. A significant nonadditive genetic effect was detected. Different expression of traits and distinct relative performances were found for reciprocal crosses involving populations located on each side of the main hybrid zone located at the Almeria-Oran front, illustrating asymmetric reproductive isolation. The poor fitness performance observed for the Western Mediterranean population of sea bass is discussed as it represents the main source of seed hatchery production, but also because it potentially illustrates nonadaptive introgression and maladaptation.

阐明物种分布范围内海洋物种的种内表型地理变异（phenogeography，表型生物地理学），是理解诸多生态进化议题的核心所在。然而，尽管具备探究适应性变异的巨大潜力，表型生物地理学研究却远不如系统发生生物地理学（phylogeography）研究受关注，后者仍主要聚焦于中性分子标记。在海洋物种中，基因型与表型数据如何在大地理尺度上协同变异，目前仍知之甚少。本研究以极具商业价值的海洋鱼类欧洲海鲈（Dicentrarchus labrax）的集合种群为研究对象，为探究其早期存活率与性比的地理变异，采用因子设计双列杂交（factorial diallel cross）方案，将75个非近交父本（源自5个地理种群）与26个母本（源自2个地理种群，分别位于杂交带两侧）进行杂交。共构建全同胞家系1950个，并在统一可控环境下开展养殖培育。利用7个微卫星（microsatellite）标记对7200个个体进行了亲权鉴定。广义线性模型分析结果显示，两个性状均存在显著的加性遗传效应，且性状间存在多效性（pleiotropy）；同时检测到显著的非加性遗传效应。针对位于阿尔梅里亚-奥兰锋面（Almeria-Oran front）主要杂交带两侧种群的互交组合，研究发现其性状表达模式与相对表现均存在显著差异，这表明存在不对称的生殖隔离。本研究最后对西地中海海鲈种群表现出的低适合度进行了讨论：该种群是当前海鲈苗种繁育生产的主要亲本来源，其低适合度或可反映非适应性渐渗（nonadaptive introgression）与适应不良（maladaptation）现象。