Causes and consequences of variation in maternal effects in the wild

在生命早期经历的条件可能对个人健康有很大的影响。这些早期生命效应的一个重要来源是产前和产后母亲护理的变化-因此称为"母亲效应"，定义为母亲的表型对其后代表型的影响超过了遗传自她的基因的直接影响。母亲效应的变化可能很大，至少与环境或个体自身基因的影响一样大。然而，在自然界中对这些影响的调查少得惊人，而不是实验室或农场种群，因此它们的重要性和进化后果尚未得到充分评估;如果这些母体效应是遗传的，它们可能是进化中的一个主要制约因素。在这项研究中，我们将调查的原因和后果的母亲的影响，在个别监测红鹿的朗姆酒，苏格兰岛。这是一个特别合适的研究群体，因为雄性不参与父母的照顾，而雌性在很长的生命周期内产生许多小牛。在这一群体中，母体对后代性状的影响很大;结合完整的系谱信息、高密度基因分型数据和生活史数据，该系统是表征母体遗传对后代表型的影响的大小、方向和基因组位置的极好候选者。我们的目标是首先，估计一系列性状的变化，如出生体重和幼仔存活率，这些性状可以通过不同类型的母体效应来解释：永久的环境影响，如由于母亲自身的养育条件和由于母亲之间的加性遗传变异（即可以响应定向选择的遗传变异）。其次，我们将确定这些母体效应与小牛的性别、母亲的生殖状态、怀孕期间的环境条件和母亲的年龄之间的差异（相互作用）。一般来说，我们预计随着所需投资的增加（儿子比女儿更昂贵）或条件变得更加艰难，母体效应方差会增加，但反过来也是可能的。第三，我们将使用项目期间获得的早期牛奶质量，寄生虫负荷和抗体产生的新表型，从粪便和新生儿血液样本中非侵入性地估计，以调查我们可以解释先前记录的母体效应的程度。第四，我们将使用基因组信息来研究母体遗传效应的基因组位置，首先考虑每个染色体（染色体划分），然后考虑每个染色体的较小区域（区域遗传力，全基因组关联）。我们的建议的最终目的是解决进化研究中的一个主要难题。在大多数情况下，自然选择倾向于更大的体型，大多数体型特征是可遗传的，但物种不会随着时间的推移改变体型。解释这种停滞的一个假设是，母亲的遗传和选择产生了限制。因此，母亲的基因可能会影响后代的身体大小独立于后代的基因（母亲的加性遗传效应），并可能有一个负的遗传相关性之间的母亲的遗传效应和后代自己的遗传效应对性状。这种遗传相关性是否作为一种进化约束，关键取决于对后代性状和母体对该性状的选择的强度和方向。我们打算在自由生活的人口中首次测量测试进化约束预测所需的所有参数。

Conditions experienced during early life can have large impacts on individual fitness. An important source of these early life effects is variation in pre- and postnatal maternal care - hence 'maternal effects', defined as the influence of a mother's phenotype on the phenotype of her offspring over and above the direct effect of genes inherited from her. Variation in maternal effects can be large, at least as large as that due to influences of the environment or of an individual's own genes. However, there are strikingly few investigations of these effects in natural as opposed to laboratory or farm populations and so their importance and evolutionary consequences have not been fully assessed; if these maternal effects are genetic in origin, they could be a major source of constraint in evolution. In this study we will investigate the causes and consequences of maternal effects in the individually-monitored red deer of the Isle of Rum, Scotland. This is a particularly appropriate study population as males play no part in parental care, whilst females produce many calves over long lifetimes. Maternal effects on offspring traits are known to be large in this population; combined with complete pedigree information, high density genotyping data and life history data, this system is an excellent candidate for characterising the magnitude, direction and genomic location of maternal genetic effects on offspring phenotype.Our aims are first, to estimate the variation in a range of traits such as birth weight and juvenile survival that is explained by different kinds of maternal effects: permanent environment effects such as those due to a mother's own rearing conditions and those due to additive genetic variation between mothers (i.e. genetic variation that can respond to directional selection). Second, we will determine the extent to which these maternal effects vary (interact) with the sex of the calf, the reproductive status of the mother, environmental conditions during pregnancy and the mother's age. Generally we expect maternal effects variance to increase as the investment required gets greater (sons more costly than daughters) or the conditions get tougher, but the reverse is also possible. Third, we will use new phenotypes obtained during the project for early milk quality, parasite load and antibody production, estimated non-invasively from faecal and neonatal blood samples, to investigate the extent to which we can explain the maternal effects documented earlier. Fourth, we will use genomic information to investigate the genomic location of maternal genetic effects, first by considering each chromosome in turn (chromosome partitioning), then by considering smaller regions of each chromosome (regional heritability, genome-wide association).The final and ultimate aim of our proposal is to address a major puzzle in evolutionary research. In most cases where it has been measured, natural selection favours larger body size, and most body size traits are heritable, and yet species do not change body size over time. One hypothesis explaining this stasis is that there are constraints arising from the genetics of and selection on mothers. Thus, a mother's genes may affect offspring body size independently of the offspring's genes (maternal additive genetic effect) and there may be a negative genetic correlation between the maternal genetic effect and the offspring's own genetic effect on a trait. Whether this genetic correlation acts as an evolutionary constraint depends critically on the strength and direction of selection on both the offspring trait and maternal performance for this trait. We intend to measure all the parameters required to test the prediction of evolutionary constraint for the first time in a free-living population.