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.

从进化、保护及经济与农业视角来看，分离种群（segregating populations）间的远交（outbreeding）具有重要研究价值。尽管母源效应（maternal effects）对子代早期存活具有显著影响，且众多类群（taxa）中均存在远交带来的适合度效应（fitness effects），但野生种群中远交是否以及如何影响母源效应，相关研究仍较为匮乏。我们在统一实验室环境下，针对野生与驯化大西洋鲑（Salmo salar）种群间的多代杂交（multigenerational crosses，直至培育至第三代杂交后代）的卵黄营养期（yolk-feeding stage）多个性状展开了研究。通过杂交均值分析（cross-means analysis），我们推断：多数子代性状由母本加性远交效应（maternal additive outbreeding effects）主导，而卵黄质量同时受母本显性效应（maternal dominant effects）调控。受加性与显性母本调控性状间相互作用的影响，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）占总质量的比例过高。该子代的剩余卵黄质量较其他杂交组合高出23%~97%，较纯加性模型（additive model）的预测值高出31%。子代加性效应、上位性效应（epistatic）以及子代-母本上位性远交效应（epistatic offspring-by-maternal outbreeding effects），进一步修饰了这一以母本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）占比的提升而增大。由于表型-环境互作（phenotype-by-environment interactions）尚未明确，远交的适合度效应仍难以推断。但本研究结果揭示了：将分化种群（divergent populations）的等位基因结合后，会从机制层面破坏协同适应的遗传母本对子代早期发育的调控。母本与子代层面均存在复杂的远交效应，这使得杂交表型（hybrid phenotypes）的预测难度大幅提升。