LaBarbera Katie, Marsh Kyle J, Hayes Kia R R, Hammond Talisin T
Museum of Vertebrate Zoology, Department of Integrative Biology, University of California - Berkeley, Berkeley CA 94720, USA.
Point Blue Conservation Science, 3820 Cypress Drive, Ste #11, Petaluma, CA 94954, USA.
R Soc Open Sci. 2020 Apr 15;7(4):192203. doi: 10.1098/rsos.192203. eCollection 2020 Apr.
Species increasingly face environmental extremes. Morphological responses to changes in average environmental conditions are well documented, but responses to environmental extremes remain poorly understood. We used museum specimens to investigate relationships between a thermoregulatory morphological trait, bird bill surface area (SA) and a measure of short-term relative temperature extremity (RTE), which quantifies the degree that temperature maxima or minima diverge from the 5-year norm. Using a widespread, generalist species, , we found that SA exhibited different patterns of association with RTE depending on the overall temperature regime and on precipitation. While thermoregulatory function predicts larger SA at higher RTE, we found this only when the RTE existed in an environmental context that opposed it: atypically cold minimum temperature in a warm climate, or atypically warm maximum temperature in a cool climate. When environmental context amplified the RTE, we found a negative relationship between SA and RTE. We also found that the strength of associations between SA and RTE increased with precipitation. Our results suggest that trait responses to environmental variation may qualitatively differ depending on the overall environmental context, and that environmental change that extremifies already-extreme environments may produce responses that cannot be predicted from observations in less-extreme contexts.
物种越来越多地面临极端环境。对平均环境条件变化的形态学响应已有充分记录，但对极端环境的响应仍知之甚少。我们利用博物馆标本研究了一种体温调节形态特征——鸟类喙表面积（SA）与短期相对温度极值（RTE）的一种度量之间的关系，RTE量化了温度最大值或最小值偏离5年平均值的程度。以一种分布广泛的广布种为例，我们发现SA与RTE的关联模式因总体温度状况和降水量而异。虽然体温调节功能预测在较高的RTE下SA会更大，但我们仅在RTE存在于与其相反的环境背景中时才发现这一点：温暖气候下非典型的低温最小值，或凉爽气候下非典型的高温最大值。当环境背景加剧了RTE时，我们发现SA与RTE之间呈负相关。我们还发现SA与RTE之间关联的强度随降水量增加。我们的结果表明，性状对环境变化的响应可能因总体环境背景而在性质上有所不同，而且使已经极端的环境更加极端的环境变化可能会产生无法从较不极端背景下的观察结果预测的响应。
