INRA French National Institute for Agricultural Research, UMR 1137 Ecologie et Ecophysiologie Forestières, Champenoux, F-54280, France.
Ecologie et Ecophysiologie Forestières, UMR1137, Université de Lorraine, Vandoeuvre Les Nancy, F-54500, France.
Ecol Appl. 2017 Mar;27(2):446-457. doi: 10.1002/eap.1448. Epub 2017 Feb 16.
Species distribution models (SDMs), which statistically relate species occurrence to climatic variables, are widely used to identify areas suitable for species growth under future climates and to plan for assisted migration. When SDMs are projected across times or spaces, it is assumed that species climatic requirements remain constant. However, empirical evidence supporting this assumption is rare, and SDM predictions could be biased. Historical human-aided movements of tree species can shed light on the reliability of SDM predictions in planning for assisted migration. We used Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), a North American conifer introduced into Europe during the mid-19th century, as a case-study to test niche conservatism. We combined transcontinental data sets of Douglas-fir occurrence and climatic predictors to compare the realized niches between native and introduced ranges. We calibrated a SDM in the native range and compared areas predicted to be climatically suitable with observed presences. The realized niches in the native and introduced ranges showed very limited overlap. The SDM calibrated in North America had very high predictive power in the native range, but failed to predict climatic suitability in Europe where Douglas-fir grows in climates that have no analogue in the native range. We review the ecological mechanisms and silvicultural practices that can trigger such shifts in realized niches. Retrospective analysis of tree species introduction revealed that the assumption of niche conservatism is erroneous. As a result, distributions predicted by SDM are importantly biased. There is a high risk that assisted migration programs may be misdirected and target inadequate species or introduction zones.
物种分布模型（SDMs）通过统计方法将物种的出现与气候变量联系起来，广泛用于识别未来气候下适合物种生长的区域，并为辅助迁移做规划。当 SDM 被用于跨时间或空间的预测时，通常假设物种的气候需求保持不变。然而，支持这一假设的经验证据很少，SDM 预测可能存在偏差。历史上人类对树种的辅助迁移可以为 SDM 预测在辅助迁移规划中的可靠性提供一些启示。我们以北美冷杉（Pseudotsuga menziesii (Mirb.) Franco）为例，研究了物种分布模型的预测在辅助迁移规划中的可靠性。这种树种在 19 世纪中期被引入欧洲，是一种被广泛研究的案例。我们将北美冷杉的跨大陆发生数据与气候预测因子相结合，比较了其在原生和引入范围的实现生态位。我们在原生范围内校准了一个 SDM，并将预测的气候适宜区域与观察到的存在区域进行了比较。在原生和引入范围的实现生态位之间的重叠非常有限。在北美的 SDM 校准中，在原生范围内具有非常高的预测能力，但在欧洲，它无法预测冷杉生长的气候条件，因为这些条件在原生范围内没有类似的气候。我们回顾了可能引发这种实现生态位变化的生态机制和造林实践。对树种引种的回顾性分析表明，生态位保守性的假设是错误的。因此，SDM 预测的分布存在重要的偏差。辅助迁移计划可能会被误导，目标物种或引入区域可能不合适，存在很高的风险。
