Data from: Long-term fitness consequences of early environment in a long-lived ungulate

Cohort effects can be a major source of heterogeneity and play an important role in population dynamics. Silver-spoon effects, when environmental quality at birth improves future performance regardless of the adult environment, can induce strong lagged responses on population growth. Alternatively, the external predictive adaptive response (PAR) hypothesis predicts that organisms will adjust their developmental trajectory and physiology during early life in anticipation of expected adult conditions but has rarely been assessed in wild species. We used over 40 years of detailed individual monitoring of bighorn ewes (Ovis canadensis) to quantify long-term cohort effects on survival and reproduction. We then tested both the silver-spoon and the PAR hypotheses. Cohort effects involved a strong interaction between birth and current environments: reproduction and survival were lowest for ewes that were born and lived at high population densities. This interaction, however, does not support the PAR hypothesis because individuals with matching high-density birth and adult environments had reduced fitness. Instead, individuals born at high density had overall lower lifetime fitness suggesting a silver-spoon effect. Early-life conditions can induce long-term changes in fitness components, and their effects on cohort fitness vary according to adult environment.队列效应（Cohort effects）是种群异质性的重要来源，且在种群动态中发挥关键作用。银匙效应（Silver-spoon effects）指个体出生时所处的环境质量可提升其未来的表现，且不受成年后环境的影响，该效应可对种群增长诱发强烈的滞后响应。与之相对，外部预测性适应反应（PAR）假说预测，生物会在早期发育阶段，根据预期的成年环境条件调整自身的发育轨迹与生理状态，但该假说在野生种群中鲜有实证验证。我们依托历时四十余年的大角羊母羊（Ovis canadensis）个体详细监测数据，量化了队列效应对个体存活与繁殖的长期影响，并同时检验了银匙效应与PAR假说。研究结果显示，队列效应体现为出生环境与当前成年环境间的强烈交互作用：在高种群密度环境下出生且成年后仍栖息于高密度环境的母羊，其繁殖能力与存活概率均处于最低水平。然而这一交互结果并不支持PAR假说，因为出生与成年环境均为高密度的个体，其适合度（fitness）反而有所降低。与之相反，在高密度环境下出生的个体，整体终身适合度显著更低，这一结果印证了银匙效应的存在。早期生活环境可对适合度组分产生长期影响，且其对队列适合度的效应会随成年环境的变化而发生改变。