Data from: Significant differences in maternal carotenoid provisioning and effects on offspring fitness in Chinook salmon colour morphs

In oviparous species, maternal carotenoid provisioning can deliver diverse fitness benefits to offspring via increased survival, growth, and immune function. Despite demonstrated advantages of carotenoids, large intra‐ and interspecific variation in carotenoid utilization exists, suggesting trade‐offs associated with carotenoids. In Chinook salmon (Oncorhynchus tshawytscha), extreme variation in carotenoid utilization delineates two colour morphs (red and white) that differ genetically in their ability to deposit carotenoids into tissues. Here, we take advantage of this natural variation to examine how large differences in maternal carotenoid provisioning influence offspring fitness. Using a full‐factorial breeding design crossing morphs and common‐garden rearing, we measured differences in a suite of fitness‐related traits, including survival, growth, viral susceptibility, and host response, in offspring of red (carotenoid‐rich eggs) and white (carotenoid‐poor eggs) females. Eggs of red females had significantly higher carotenoid content than those of white females (6X more); however, this did not translate into measurable differences in offspring fitness. Given that white Chinook salmon may have evolved to counteract their maternal carotenoid deficiency, we also examined the relationship between egg carotenoid content and offspring fitness within each morph separately. Egg carotenoids only had a positive effect within the red morph on survival to eyed‐egg (earliest measured trait), but not within the white morph. While previous work shows that white females benefit from reduced egg predation, our study also supports a hypothesis that white Chinook salmon have evolved additional mechanisms to improve egg survival despite low carotenoids, providing novel insight into evolutionary mechanisms that maintain this stable polymorphism.在卵生动物类群中，母体类胡萝卜素（carotenoid）供给可通过提升子代存活率、生长速率与免疫功能，为后代带来多样的适合度收益。尽管类胡萝卜素的益处已得到实证支持，但其利用效率存在显著的种内与种间变异，这提示类胡萝卜素存在相关的权衡（trade-off）效应。在奇努克鲑（Oncorhynchus tshawytscha）中，类胡萝卜素利用效率的极端差异划分出两种体色形态（红色与白色），二者在将类胡萝卜素沉积至组织的遗传能力上存在显著差异。本研究利用这一天然变异，探究母体类胡萝卜素供给的显著差异如何影响子代适合度。研究采用跨形态的全因子繁育设计与同质园饲养方案，对红色（类胡萝卜素富集型卵）与白色（类胡萝卜素匮乏型卵）雌性亲本的子代开展检测，测量了一系列与适合度相关的性状差异，包括存活率、生长速率、病毒易感性与宿主免疫应答反应。红色雌性亲本的卵类胡萝卜素含量显著高于白色雌性（高出6倍），但这一差异并未转化为子代适合度的可检测差异。鉴于白色型奇努克鲑可能已演化出应对母体类胡萝卜素缺乏的补偿策略，本研究还分别在两种形态内部，探究了卵类胡萝卜素含量与子代适合度之间的关联。仅在红色形态中，卵类胡萝卜素对发育至眼胚期（首个检测性状）的存活率具有正向效应，而在白色形态中未观察到此效应。尽管已有研究表明白色型雌性亲本可通过降低卵被捕食的概率获得收益，但本研究同样支持以下假说：白色型奇努克鲑已演化出额外机制，以在类胡萝卜素水平较低的情况下提升卵的存活率，这为维持这一稳定多态性的演化机制提供了全新的研究视角。