Department of Animal Behaviour, Bielefeld University, Germany.
Department of Animal Behaviour, Bielefeld University, Germany; Max Planck Institute for Evolutionary Biology, Plön, Germany.
Horm Behav. 2020 Jun;122:104747. doi: 10.1016/j.yhbeh.2020.104747. Epub 2020 Apr 13.
Consistent between-individual differences in behaviour have been documented across the animal kingdom. Such variation between individuals has been shown to be the basis for selection and to act as a pacemaker for evolutionary change. Recently, equivocal evidence suggests that such consistent between-individual variation is also present in hormones. This observation has sparked interest in understanding the mechanisms shaping individual differences, temporal consistency and heritability of hormonal phenotypes and to understand, if and to what extent hormonal mechanisms are involved in mediating consistent variation in behaviour between individuals. Here, we used zebra finches of the fourth generation of bi-directionally selected lines for three independent behaviours: aggression, exploration and fearlessness. We investigated how these behaviours responded to artificial selection and tested their repeatability. We further tested for repeatability of corticosterone and testosterone across and within lines. Moreover, we are presenting the decomposed variance components for within-individual variance (i.e. flexibility) and between-individual variance (i.e. more or less pronounced differences between individuals) and investigate their contribution to repeatability estimates. Both hormones as well as the exploration and fearlessness but not aggressiveness, were repeatable. However, variance components and hence repeatability differed between lines and were often lower than in unselected control animals, mainly because of a reduction in between-individual variance. Our data show that artificial selection (including active selection and genetic drift) can affect the mean and variance of traits. We stress the importance for understanding how variable a trait is both between and within individuals to assess the selective value of a trait.
动物王国中已有大量关于行为个体间一致性差异的记录。个体间的这种差异已被证明是选择的基础，并作为进化变化的起搏器。最近，有争议的证据表明，激素中也存在这种一致的个体间变异。这一观察结果引发了人们对理解塑造个体差异、激素表型的时间一致性和遗传性的机制的兴趣，并探讨了激素机制是否以及在何种程度上参与了个体间行为的一致性变化。在这里，我们使用了第四代双向选择的斑马雀进行了三个独立行为的研究：攻击性、探索性和无畏性。我们研究了这些行为如何对人工选择做出反应，并测试了它们的可重复性。我们进一步测试了皮质酮和睾酮在个体间和个体内的可重复性。此外，我们还提出了个体内方差（即灵活性）和个体间方差（即个体之间差异的明显程度）的分解方差分量，并研究了它们对可重复性估计的贡献。两种激素以及探索性和无畏性，但不是攻击性，都是可重复的。然而，方差分量，因此可重复性，在个体间和个体内都存在差异，而且通常低于未选择的对照动物，主要是因为个体间方差的减少。我们的数据表明，人工选择（包括主动选择和遗传漂变）可以影响特征的平均值和方差。我们强调了理解一个特征在个体间和个体内的可变性的重要性，以评估一个特征的选择价值。
