Araya-Ajoy Yimen G, Dingemanse Niels J
Research Group Evolutionary Ecology of Variation, Max Planck Institute for Ornithology, Seewiesen, Germany.
Center for Biodiversity Dynamics, Norwegian University of Science and Technology, Trondheim, Norway.
J Anim Ecol. 2017 Mar;86(2):227-238. doi: 10.1111/1365-2656.12621.
Labile characters allow individuals to flexibly adjust their phenotype to changes in environmental conditions. There is growing evidence that individuals can differ both in average expression and level of plasticity in this type of character. Both of these aspects are studied in conjunction within a reaction norm framework. Theoreticians have investigated the factors promoting variation in reaction norm intercepts (average phenotype) and slopes (level of plasticity) of a key labile character: behaviour. A general prediction from their work is that selection will favour the evolution of repeatable individual variation in level of plasticity only under certain ecological conditions. While factors promoting individual repeatability of plasticity have thus been identified, empirical estimates of this phenomenon are largely lacking for wild populations. We assayed aggressiveness of individual male great tits (Parus major) twice during their egg-laying stage and twice during their egg-incubation stage to quantify each male's level of seasonal plasticity. This procedure was applied during six consecutive years; all males breeding in our plots during those years were assayed, resulting in repeated measures of individual reaction norms for any individual breeding in multiple years. We quantified among- and within-individual variation in reaction norm components, allowing us to estimate repeatability of seasonal plasticity. Using social pedigree information, we further partitioned reaction norm components into their additive genetic and permanent environmental counterparts. Cross-year individual repeatability for the intercepts (average aggressiveness) and slopes (level of seasonal plasticity) of the aggressiveness reaction norms were 0·574 and 0·516 respectively. The mean of the posterior distributions suggested modest heritabilities (h = 0·260 for intercepts; h = 0·266 for slopes), but these estimates were relatively uncertain. Males behaved more aggressively in areas with higher breeding densities, and became less aggressive and less plastic with increasing age; plasticity thus varied within individuals and was multidimensional in nature. This empirical study quantified cross-year individual repeatability, heritability and age-related reversible plasticity in behaviour. Acknowledging such patterns of multi-level variation is important not only for testing behavioural ecology theory concerning the evolution of repeatable differences in behavioural plasticity but also for predicting how reversible plasticity may evolve in natural populations.
易变性状使个体能够根据环境条件的变化灵活调整其表型。越来越多的证据表明，个体在这类性状的平均表达和可塑性水平上可能存在差异。在反应规范框架内，这两个方面都被结合起来进行研究。理论学家们研究了促进关键易变性状——行为的反应规范截距（平均表型）和斜率（可塑性水平）发生变化的因素。他们研究得出的一个普遍预测是，只有在特定的生态条件下，选择才会有利于可塑性水平上可重复的个体差异的进化。虽然促进可塑性个体重复性的因素已被确定，但对于野生种群中这一现象的实证估计却大多缺乏。我们在雄性大山雀（Parus major）的产卵期和孵卵期各对其攻击性进行了两次测定，以量化每只雄性的季节性可塑性水平。这一过程连续进行了六年；对那些年在我们研究区域内繁殖的所有雄性都进行了测定，从而得到了对多年繁殖的任何个体的反应规范的重复测量结果。我们量化了反应规范成分的个体间和个体内变异，从而能够估计季节性可塑性的重复性。利用社会谱系信息，我们进一步将反应规范成分划分为加性遗传成分和永久环境成分。攻击性反应规范的截距（平均攻击性）和斜率（季节性可塑性水平）的跨年个体重复性分别为0·574和0·516。后验分布的均值表明遗传力适中（截距的h = 0·260；斜率的h = 0·266），但这些估计相对不太确定。雄性在繁殖密度较高的区域表现得更具攻击性，并且随着年龄增长攻击性和可塑性都会降低；因此，可塑性在个体内部有所变化，且本质上是多维度的。这项实证研究量化了行为的跨年个体重复性、遗传力以及与年龄相关的可逆可塑性。认识到这种多层次变异模式不仅对于检验有关行为可塑性中可重复差异进化的行为生态学理论很重要，而且对于预测自然种群中可逆可塑性可能如何进化也很重要。
