Pick Joel L, Postma Erik, Tschirren Barbara
Department of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstrasse 190 8057 Zurich Switzerland.
Institute of Evolutionary Biology School of Biological Sciences, University of Edinburgh Edinburgh EH9 3JT United Kingdom.
Evol Lett. 2019 Jul 2;3(4):412-423. doi: 10.1002/evl3.125. eCollection 2019 Aug.
Maternal effects are prevalent in nature and significantly contribute to variation in phenotypic trait expression. However, little attention has been paid to the factors shaping variation in the traits mediating these effects (maternal effectors). Specific maternal effectors are often not identified, and typically they are assumed to be inherited in an additive genetic and autosomal manner. Given that these effectors can cause long-lasting effects on offspring phenotype, it is likely that they may also affect themselves in the next generation. Although the existence of such cascading maternal effects has been discussed and modeled, empirical examples of such effects are rare, let alone quantitative estimates of their strength and evolutionary consequences. Here, we demonstrate that the investment a mother makes in her eggs positively affects the egg investment of her daughters. Through reciprocally crossing artificially selected lines for divergent prenatal maternal investment in Japanese quail (), we demonstrate that the size of eggs daughters lay resembles the egg size of their maternal line significantly more than that of their paternal line, highlighting that egg size is in part maternally inherited. Correspondingly, we find that variation in the daughters' egg size is in part determined by maternal identity, in addition to substantial additive genetic effects. Furthermore, this maternal variance in offspring egg size is fully explained by maternal egg size, demonstrating the presence of a positive cascading effect of maternal egg size on offspring egg size. Finally, we use an evolutionary model to quantify the consequences of covariance between cascading maternal and additive genetic effects for both maternal effector and offspring body mass evolution. Our study demonstrates that by amplifying the amount of variation available for selection to act on, positive cascading maternal effects can significantly enhance the evolutionary potential of maternal effectors and the offspring traits that they affect.
母体效应在自然界中普遍存在，并显著促成表型性状表达的变异。然而，对于塑造介导这些效应的性状（母体效应因子）变异的因素，人们关注甚少。具体的母体效应因子往往未被识别，通常假定它们以加性遗传和常染色体方式遗传。鉴于这些效应因子可对后代表型产生持久影响，它们很可能在下一代中也会影响自身。尽管已经讨论并建立了这种级联母体效应的模型，但此类效应的实证例子却很罕见，更不用说对其强度和进化后果的定量估计了。在此，我们证明母亲对其卵的投入会对其女儿的卵投入产生积极影响。通过对日本鹌鹑进行产前母体投入差异的人工选择品系的正反交，我们证明女儿所产蛋的大小与其母系的蛋大小相似程度显著高于父系，这突出表明蛋大小部分是母系遗传的。相应地，我们发现除了大量的加性遗传效应外，女儿蛋大小的变异部分由母体身份决定。此外，后代蛋大小的这种母体方差完全由母体蛋大小解释，证明了母体蛋大小对后代蛋大小存在正向级联效应。最后，我们使用一个进化模型来量化级联母体效应和加性遗传效应之间的协方差对母体效应因子和后代体重进化的影响。我们的研究表明，通过扩大可供选择作用的变异量，正向级联母体效应可显著增强母体效应因子及其所影响的后代性状的进化潜力。
