Data from: Multigenerational hybridisation and its consequences for maternal effects in Atlantic salmon

Outbreeding between segregating populations can be important from an evolutionary, conservation, and economical- agricultural perspective. Whether and how outbreeding influences maternal effects in wild populations has rarely been studied, despite both the prominent maternal influence on early offspring survival and the known presence of fitness effects resulting from outbreeding in many taxa. We studied several traits during the yolk-feeding stage in multigenerational crosses between a wild and a domesticated Atlantic salmon (Salmo salar) population up to their third-generation hybrid in a common laboratory environment. Using cross-means analysis, we inferred that maternal additive outbreeding effects underlie most offspring traits, but that yolk mass also underlies maternal dominant effects. As a consequence of the interplay between additive and dominant maternally controlled traits, offspring from first-generation hybrid mothers expressed an excessive proportion of residual yolk mass, relative to total mass, at time of first feeding. Their residual yolk mass was 23-97% greater than those of other crosses and 31% more than that predicted by a purely additive model. Offspring additive, epistatic, and epistatic offspring-by-maternal outbreeding effects appeared to further modify this largely maternally controlled cross-means pattern, resulting in an increase in offspring size with the percentage of domesticated alleles. Fitness implications remain elusive because of unknown phenotype- by-environment interactions. However, these results suggest how mechanistically co-adapted genetic maternal control on early offspring development can be disrupted by the effects of combining alleles from divergent populations. Complex outbreeding effects at both the maternal and offspring levels make the prediction of hybrid phenotypes difficult.分离种群（segregating populations）间的远交（outbreeding），从进化生物学、保护生物学以及经济农业视角来看均具有重要意义。尽管母体对子代早期存活具有显著影响，且众多类群（taxa）中均已证实远交可产生适合度效应（fitness effects），但野生种群中远交如何以及是否会影响母体效应（maternal effects）的相关研究仍较为匮乏。本研究在统一实验室环境下，对野生与驯化大西洋鲑（Atlantic salmon, *Salmo salar*）种群间的多代杂交组合展开研究，直至获得第三代杂交后代，并聚焦于摄食卵黄阶段（yolk-feeding stage）的多项性状。通过杂交均值分析（cross-means analysis），我们推断多数子代性状的形成受母体加性远交效应（maternal additive outbreeding effects）调控，而卵黄质量（yolk mass）同时受母体显性效应（maternal dominant effects）影响。由于加性与显性母体调控性状间存在相互作用，第一代杂交母本所产子代在初次摄食时，其剩余卵黄质量（residual yolk mass）占总质量的比例显著偏高：该比例较其他杂交组合高出23%~97%，较纯加性模型（purely additive model）的预测值高出31%。子代加性效应、上位性（epistatic）效应以及子代-母体上位性远交效应，进一步修饰了这一以母体调控为主的杂交均值模式，使得子代体型随驯化等位基因（domesticated alleles）占比的升高而增大。由于表型-环境互作（phenotype-by-environment interactions）尚未明确，远交对适合度的影响仍难以阐明。但本研究结果揭示了：将分化种群（divergent populations）的等位基因进行融合，会破坏对子代早期发育具有机制性协同适应作用的遗传母体调控。母体与子代层面均存在复杂的远交效应，这使得杂交后代表型的预测难度大幅提升。