Data from: Genetic variation in variability: phenotypic variability of fledging weight and its evolution in a songbird population

Variation in traits is essential for natural selection to operate and genetic and environmental effects can contribute to this phenotypic variation. From domesticated populations, we know that families can differ in their level of within-family variance, which leads to the intriguing situation that within-family variance can be heritable. For offspring traits, such as birth weight, this implies that within-family variance in traits can vary among families and can thus be shaped by natural selection. Empirical evidence for this in wild populations is however lacking. We investigated whether within-family variance in fledging weight is heritable in a wild great tit (Parus major) population and whether these differences are associated with fitness. We found significant evidence for genetic variance in within-family variance. The genetic coefficient of variation (GCV) was 0.18 and 0.25, when considering fledging weight a parental or offspring trait, respectively. We found a significant quadratic relationship between within-family variance and fitness: families with low or high within-family variance had lower fitness than families with intermediate within-family variance. Our results show that within-family variance can respond to selection and provides evidence for stabilizing selection on within-family variance.

表型性状的变异是自然选择发挥作用的必要前提，遗传与环境效应均可促成此类表型变异（phenotypic variation）。通过驯化种群的相关研究，我们已知不同家系的家系内变异（within-family variance）水平存在差异，这引出了一个耐人寻味的现象：家系内变异本身可遗传。以出生体重这类子代性状为例，这意味着性状的家系内变异在不同家系间存在差异，因此可被自然选择所塑造。然而，野生种群中该现象的实证证据仍较为匮乏。本研究针对野生大山雀（Parus major）种群展开调查，旨在明确其离巢体重的家系内变异是否可遗传，以及这类变异差异是否与个体适合度相关联。我们的研究结果证实，家系内变异存在显著的遗传变异。当将离巢体重分别视为亲本性状与子代性状时，其遗传变异系数（genetic coefficient of variation, GCV）分别为0.18与0.25。我们还发现家系内变异与适合度之间存在显著的二次函数关系：家系内变异处于极低或极高水平的家系，其适合度均低于家系内变异处于中等水平的家系。本研究结果表明，家系内变异可对选择作出响应，同时为家系内变异所承受的稳定选择提供了实证依据。