Climate change may alter the signal of plant facilitation in Mediterranean drylands

Facilitation is an ecological interaction that has allowed plant lineages to survive past climate aridification. This same interaction can be expected to buffer the effects of current climate change, which is tending to become more arid in the Mediterranean basin. However, facilitation may wane when stress conditions are extreme. Here we argue that the erosion of the facilitation signal between Quercus ilex and its nurses detected by García-Fayos et al. (2020) along 50 years in the eastern Iberian Peninsula may have been due to the reversion of facilitation to competition imposed by an increasingly arid climate. To support this speculation, we reconstructed the climatic niche of Q. ilex and its nurses as well as the local climate change occurring in the populations studied. We found that the decreasing trend in precipitation is pushing Q. ilex out of its climatic optimum in the stressful (semi-arid) but not in the mild (sub-humid) habitats. These results suggest that facilitation will b..., Niche modelling: Studied species occurrences were extracted from the Global Biodiversity Information Facility (GBIF) database (GBIF 2023, www.gbif.org). For each occurrence we extracted the precipitation of that location from the CHELSA database (Karger et al. 2017, https://chelsa-climate.org). Final species datasets used for the analyses were cleaned and redundant data were droped. Precipitation trend in our study area: Studied plots precipitation were extracted from quality controlled and homogenized meteorological observations from high spatial resolution databases (González‐Hidalgo et al. 2011, 2022), , # Climate change may alter the signal of plant facilitation in Mediterranean drylands [https://doi.org/10.5061/dryad.h9w0vt4rj](https://doi.org/10.5061/dryad.h9w0vt4rj) Facilitation is an ecological interaction that has allowed plant lineages to survive past climate aridification. This same interaction can be expected to buffer the effects of current climate change, which is tending to become more arid in the Mediterranean basin. However, facilitation may wane when stress conditions are extreme. Here we argue that the erosion of the facilitation signal between Quercus ilex and its nurses detected by García-Fayos et al. (2020) along 50 years in the eastern Iberian Peninsula may have been due to the reversion of facilitation to competition imposed by an increasingly arid climate. To support this speculation, we reconstructed the climatic niche of Q. ilex and its nurses as well as the local climate change occurring in the populations studied. We found that the decreasing trend in precipi...植物促进作用（Facilitation）是一类生态交互作用，曾帮助植物类群度过过往的气候干旱化进程。当前地中海盆地正趋于气候干旱化，这类交互作用有望缓解当前气候变化带来的负面影响。然而当环境胁迫条件趋于极端时，促进作用可能会减弱。本文提出假说：伊比利亚半岛东部的冬青栎（Quercus ilex）与其保育植物（nurse plants）之间的促进作用信号在近50年间出现衰减（García-Fayos et al., 2020），这一现象或许是因日益干旱的气候使得促进作用逆转成为竞争作用所致。为验证这一推测，我们重建了冬青栎及其保育植物的气候生态位，同时还原了研究种群所在区域的局地气候变化。研究发现，降水减少的趋势正迫使冬青栎脱离其在胁迫生境（半干旱生境）中的气候最优区间，但在温和的亚湿润生境中并未出现该现象。上述结果表明，植物促进作用将…… 生态位建模（Niche modelling）： 研究物种的出现记录提取自全球生物多样性信息设施（Global Biodiversity Information Facility, GBIF）数据库（GBIF 2023, www.gbif.org）。针对每一条出现记录，我们从CHELSA气候数据库（CHELSA database）中提取对应地点的降水数据。用于分析的最终物种数据集经过清洗处理，冗余数据已被剔除。 研究区域降水趋势： 研究样地的降水数据提取自经质量控制与均一化处理的高空间分辨率气象观测数据库（high spatial resolution meteorological observation database）（González-Hidalgo et al. 2011, 2022）。 # 气候变化或改变地中海旱地的植物促进作用信号 [https://doi.org/10.5061/dryad.h9w0vt4rj](https://doi.org/10.5061/dryad.h9w0vt4rj)