Department of Earth Sciences, Montana State University, Bozeman, MT, USA.
U.S. Geological Survey, Northern Rocky Mountain Science Center, Bozeman, MT, USA.
Glob Chang Biol. 2021 Oct;27(19):4498-4515. doi: 10.1111/gcb.15793. Epub 2021 Jul 29.
Species are frequently responding to contemporary climate change by shifting to higher elevations and poleward to track suitable climate space. However, depending on local conditions and species' sensitivity, the nature of these shifts can be highly variable and difficult to predict. Here, we examine how the American pika (Ochotona princeps), a philopatric, montane lagomorph, responds to climatic gradients at three spatial scales. Using mixed-effects modeling in an information-theoretic approach, we evaluated a priori model suites regarding predictors of site occupancy, relative abundance, and elevational-range retraction across 760 talus patches, nested within 64 watersheds across the Northern Rocky Mountains of North America, during 2017-2020. The top environmental predictors differed across these response metrics. Warmer temperatures in summer and winter were associated with lower occupancy, lower relative abundances, and greater elevational retraction across watersheds. Occupancy was also strongly influenced by habitat patch size, but only when combined with climate metrics such as actual evapotranspiration. Using a second analytical approach, acute heat stress and summer precipitation best explained retraction residuals (i.e., the relative extent of retraction given the original elevational range of occupancy). Despite the study domain occurring near the species' geographic-range center, where populations might have higher abundances and be at lower risk of climate-related stress, 33.9% of patches showed evidence of recent extirpations. Pika-extirpated sites averaged 1.44℃ warmer in summer than did occupied sites. Additionally, the minimum elevation of pika occupancy has retracted upslope in 69% of watersheds (mean: 281 m). Our results emphasize the nuance associated with evaluating species' range dynamics in response to climate gradients, variability, and temperature exceedances, especially in regions where species occupy gradients of conditions that may constitute multiple range edges. Furthermore, this study highlights the importance of evaluating diverse drivers across response metrics to improve the predictive accuracy of widely used, correlative models.
物种经常通过向更高海拔和更北的地方迁移来适应当代气候变化，以追踪适宜的气候空间。然而，取决于当地条件和物种的敏感性，这些变化的性质可能高度可变且难以预测。在这里，我们研究了美国白靴兔（Ochotona princeps），一种有亲缘关系的山地兔，如何在三个空间尺度上对气候梯度做出反应。我们使用信息论中的混合效应模型，评估了 2017-2020 年在北美落基山脉北部的 64 个流域内嵌套的 760 个岩屑斑块中，站点占有率、相对丰度和海拔范围退缩的先验模型套件，以及这些反应指标的预测因子。顶级环境预测因子因这些反应指标而异。夏季和冬季的温暖温度与较低的占有率、较低的相对丰度和更大的流域海拔退缩有关。栖息地斑块大小也对占有率有强烈影响，但仅当与实际蒸散等气候指标结合使用时才会产生影响。使用第二种分析方法，急性热应激和夏季降水最好地解释了退缩残差（即给定原始占有率的海拔范围的退缩程度）。尽管研究区域位于物种地理范围的中心附近，那里的种群可能数量更多，面临与气候相关的压力的风险较低，但仍有 33.9%的斑块有最近灭绝的迹象。与有白靴兔栖息的斑块相比，白靴兔灭绝的斑块在夏季平均温度高出 1.44°C。此外，在 69%的流域（平均值：281 米）中，白靴兔占有率的最低海拔已向上坡退缩。我们的研究结果强调了在评估物种对气候梯度、变异性和温度超过的范围动态时的细微差别，尤其是在物种占据可能构成多个范围边缘的条件梯度的地区。此外，这项研究强调了在不同的反应指标中评估多种驱动因素以提高广泛使用的相关模型的预测准确性的重要性。
