Pathways through which phenotypic variation among individuals arise can be complex. One assumption often made in relation to intraspecific diversity is that the stability or predictability of the environment will interact with expression of the underlying phenotypic variation. To address biological complexity below the species level, we investigated variability across years in morphology and annual growth increments between and within two sympatric lake charr Salvelinus namaycush ecotypes in Rush Lake, USA. A rapid phenotypic shift in body and head shape was found within a decade. The magnitude and direction of the observed phenotypic change were consistent in both ecotypes, which suggests similar pathways caused the variation over time. Over the same time period, annual growth increments declined for both lake charr ecotypes and corresponded with a consistent phenotypic shift of each ecotype. Despite ecotype‐specific annual growth changes in response to winter conditions, the observed annual growth shift for both ecotypes was linked, to some degree, with variation in the environment. Particularly, a declining trend in regional cloud cover was associated with an increase of early‐stage (ages 1–3) annual growth for lake charr of Rush Lake. Underlying mechanisms causing changes in growth rates and constrained morphological modulation are not fully understood. An improved knowledge of the biology hidden within the expression of phenotypic variation promises to clarify our understanding of temporal morphological diversity and instability.

中文翻译：

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湖炭表型的时间不稳定性：与环境变量相关的生长速率和形态的同步性？

个体之间发生表型变异的途径可能很复杂。通常与种内多样性有关的一种假设是环境的稳定性或可预测性将与潜在表型变异的表达相互作用。为了解决低于物种水平的生物复杂性，我们研究了两个同胞夏尔鲑鱼Salvelinus namaycush之间和之内的形态变化和年增长率的多年变化。美国拉什湖的生态型。在十年内发现了身体和头部形状的快速表型转变。在两种生态型中观察到的表型变化的大小和方向都一致，这表明相似的途径导致了随时间的变化。在同一时期，两种湖炭生态型的年增长增量均下降，并且与每种生态型的一致表型变化相对应。尽管因冬季条件不同，特定生态类型的年增长率发生了变化，但观察到的两种生态类型的年增长率变化在一定程度上都与环境变化有关。特别是，拉什湖的夏尔湖早期（1-3岁）年增长的增加与区域云量的下降趋势有关。导致生长速率变化和形态调节受限的潜在机制尚未完全清楚。对表型变异表达中隐藏的生物学知识的进一步了解有望阐明我们对时间形态多样性和不稳定性的理解。