University of Idaho, Department of Fish and Wildlife Sciences, P.O. Box 441136, Moscow, Idaho 83844, USA.
Ecol Appl. 2013 Jun;23(4):864-78. doi: 10.1890/12-0979.1.
Although climate acts as a fundamental constraint on the distribution of organisms, understanding how this relationship between climate and distribution varies over a species' range is critical for addressing the potential impacts of accelerated climate change on biodiversity. Bioclimatic niche models provide compelling evidence that many species will experience range shifts under scenarios of global change, yet these broad, macroecological perspectives lack specificity at local scales, where unique combinations of environment, biota, and history conspire against generalizations. We explored how these idiosyncrasies of place affect the climate-distribution relationship of the American pika (Ochotona princeps) by replicating intensive field surveys across bioclimatic gradients in eight U.S. national parks. At macroecological scales, the importance of climate as a constraint on pika distribution appears unequivocal; forecasts suggest that the species' range will contract sharply in coming decades. However, the species persists outside of its modeled bioclimatic envelope in many locations, fueling uncertainty and debate over its conservation status. Using a Bayesian hierarchical approach, we modeled variation in local patterns of pika distribution along topographic position, vegetation cover, elevation, temperature, and precipitation gradients in each park landscape. We also accounted for annual turnover in site occupancy probabilities. Topographic position and vegetation cover influenced occurrence in all parks. After accounting for these factors, pika occurrence varied widely among parks along bioclimatic gradients. Precipitation by itself was not a particularly influential predictor. However, measures of heat stress appeared most influential in the driest parks, suggesting an interaction between the strength of climate effects and the position of parks along precipitation gradients. The combination of high elevation, cold temperatures, and high precipitation lowered occurrence probabilities in some parks, suggesting an upper elevational limit for pikas in some environments. Our results demonstrate that the idiosyncrasies of place influence both the nature and strength of the climate-distribution relationship for the American pika. Fine-grained, but geographically extensive, studies replicated across multiple landscapes offer insights important to assessing the impacts of climate change that otherwise may be masked at macroecological scales. The hierarchical approach to modeling provides a coherent conceptual and technical framework for gaining these insights.
虽然气候是生物分布的基本限制因素，但了解气候与分布之间的这种关系在物种范围内如何变化，对于应对加速气候变化对生物多样性的潜在影响至关重要。生物气候生态位模型提供了令人信服的证据，表明许多物种在全球变化情景下将经历分布范围的转移，但这些广泛的宏观生态观点在局部尺度上缺乏特异性，在局部尺度上，环境、生物区系和历史的独特组合不利于概括。我们通过在美国 8 个国家公园的生物气候梯度上重复密集的实地调查，探索了这些地方的特殊性如何影响美洲兔（Ochotona princeps）的气候分布关系。在宏观生态尺度上，气候作为对兔分布的限制因素的重要性似乎是明确的；预测表明，该物种的分布范围将在未来几十年内急剧收缩。然而，在许多地方，该物种在其模型生物气候范围内之外仍然存在，这加剧了对其保护状况的不确定性和争论。我们使用贝叶斯分层方法，在每个公园景观中，根据地形位置、植被覆盖、海拔、温度和降水梯度，对兔分布的局部模式变化进行建模。我们还考虑了站点占有概率的年际变化。地形位置和植被覆盖在所有公园中都影响着兔的出现。在考虑到这些因素后，兔的出现情况在各个公园的生物气候梯度上差异很大。降水本身并不是一个特别有影响力的预测因子。然而，热应激指标在最干旱的公园中最为重要，这表明气候效应的强度与公园在降水梯度上的位置之间存在相互作用。高海拔、寒冷温度和高降水的组合降低了一些公园的出现概率，这表明在某些环境中，兔的海拔上限较低。我们的研究结果表明，地方的特殊性影响了美洲兔的气候分布关系的性质和强度。在多个景观中复制的精细但地理上广泛的研究提供了评估气候变化影响的重要见解，否则这些影响可能会在宏观生态尺度上被掩盖。建模的分层方法为获得这些见解提供了一个连贯的概念和技术框架。
