Data from: Within-individual canalization contributes to age-related increases in trait repeatability: a longitudinal experiment in red knots

Abstract: Age-related increases in the repeatable expression of labile
phenotypic traits are often assumed to arise from an increase in
among-individual variance due to differences in developmental plasticity
or by means of state-behaviour feedbacks. However, age-related increases
in repeatability could also arise from a decrease in within-individual
variance as a result of stabilizing trait expression, i.e. canalization.
Here we describe age-related changes in within- and among-individual
variance components in two correlated traits, gizzard mass and exploration
behavior, in a medium-sized shorebird, the red knot (Calidris canutus).
Increased repeatability of gizzard mass came about due to an increase in
among-individual variance, unrelated to differences in developmental
plasticity, together with decreases in within-individual variance,
consistent with canalization. We also found canalization of exploration,
but no age-related increase in overall repeatability, which suggests that
showing predictable expression of exploration behaviour may be
advantageous from a very young age onward. Contrasts between juveniles and
adults in the first year after their capture provide support for the idea
that environmental conditions play a key role in generating
among-individual variation in both gizzard mass and exploration behavior.
Our study shows that stabilization of traits occurs under constant
conditions: with increased exposure to predictable cues, individuals may
become more certain in their assessment of the environment allowing traits
to become canalized.

摘要：学界普遍认为，易变表型性状的可重复性表达随年龄增长的现象，源于发育可塑性差异或状态-行为反馈所导致的个体间方差升高。然而，表型重复率随年龄的提升也可能源自性状稳定表达所带来的个体内方差降低，即渠化作用（canalization）。本研究以中型滨鸟红腹滨鹬（Calidris canutus）为研究对象，针对肌胃质量与探索行为这两个相关性状，分析了其个体内与个体间方差组分随年龄的变化规律。肌胃质量的表型重复率提升，源于与发育可塑性差异无关的个体间方差升高，以及个体内方差降低，这一结果与渠化作用的理论预期一致。本研究同时发现探索行为存在渠化现象，但整体表型重复率并未随年龄出现显著提升，这提示从幼年期开始，可预测的探索行为表达便具备适应性优势。对捕获后第一年的幼鸟与成鸟进行的对比分析，为“环境条件是驱动肌胃质量与探索行为产生个体间差异的关键因素”这一观点提供了支持。本研究证实，性状稳定化发生于恒定环境条件下：当个体接触到更多可预测的环境线索时，其对环境的评估会更为精准，从而促使性状发生渠化。