Natural history collections provide an unparalleled resource for documenting population responses to past anthropogenic change. However, in many cases, traits measured on specimens may vary temporally in response to a number of different anthropogenic pressures or demographic processes. While teasing apart these different drivers is challenging, approaches that integrate analyses of spatial and temporal series of specimens can provide a robust framework for examining whether traits exhibit common responses to ecological variation in space and time. We applied this approach to analyze bill morphology variation in California Savannah Sparrows (Passerculus sandwichensis). We found that bill surface area increased in birds from higher salinity tidal marshes that are hotter and drier. Only the coastal subspecies, alaudinus, exhibited a significant increase in bill size through time. As with patterns of spatial variation, alaudinus populations occupying higher salinity tidal marshes that have become warmer and drier over the past century exhibited the greatest increases in bill surface area. We also found a significant negative correlation between bill surface area and total evaporative water loss (TEWL) and estimated that observed increases in bill size could result in a reduction of up to 16.2% in daily water losses. Together, these patterns of spatial and temporal variation in bill size were consistent with the hypothesis that larger bills are favored in freshwater‐limited environments as a mechanism of dissipating heat, reducing reliance on evaporative cooling, and increasing water conservation. With museum collections increasingly being leveraged to understand past responses to global change, this work highlights the importance of considering the influence of many different axes of anthropogenic change and of integrating spatial and temporal analyses to better understand the influence of specific human impacts on population change over time.

中文翻译：

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空间异质人为变化对沿海鸣鸟喙尺寸演化的影响


自然历史收藏为记录人口对过去人为变化的反应提供了无与伦比的资源。然而，在许多情况下，样本上测量的性状可能会因许多不同的人为压力或人口统计过程而暂时变化。虽然区分这些不同的驱动因素具有挑战性，但整合样本的空间和时间系列分析的方法可以提供一个强大的框架，用于检查性状是否对空间和时间的生态变化表现出共同的反应。我们应用这种方法来分析加州萨凡纳麻雀（ Passerculus sanddensis ）的喙形态变化。我们发现，生活在盐度较高且更热、更干燥的潮汐沼泽中的鸟类的喙表面积有所增加。随着时间的推移，只有沿海亚种alaudinus 的喙尺寸显着增加。与空间变化模式一样，居住在盐度较高的潮汐沼泽的阿劳迪努斯种群在过去一个世纪变得更加温暖和干燥，其喙表面积的增加最大。我们还发现水嘴表面积和总蒸发水损失 (TEWL) 之间存在显着的负相关性，并估计观察到的水嘴尺寸的增加可能会导致每日水损失减少高达 16.2%。总之，钞票大小的这些空间和时间变化模式与这样的假设是一致的：在淡水有限的环境中，较大的钞票更受青睐，作为一种散热机制，减少对蒸发冷却的依赖，并增加节水。 随着博物馆藏品越来越多地被用来了解过去对全球变化的反应，这项工作强调了考虑人为变化的许多不同轴的影响以及整合时空分析的重要性，以更好地了解特定人类影响对人口变化的影响。时间。