Hernández Catalina, Venegas-González Alejandro, Santini Luiz, Craven Dylan
Escuela de Ingeniería Forestal, Universidad Mayor, Camino La Pirámide 5750, Huechuraba, Santiago, Chile.
Instituto de Ciencias Agroalimentarias, Animales y Ambientales (ICA3), Universidad de O'Higgins, San Fernando, Chile.
Ann Bot. 2025 Aug 16;135(7):1459-1474. doi: 10.1093/aob/mcaf052.
Climate change is altering biodiversity by shifting species ranges. Yet, the mechanisms underlying these shifts are not well understood for plants, whose responses to changes in precipitation or temperature are often idiosyncratic. Here, we evaluated whether ecological strategies mediate tree growth and whether intraspecific trait diversity shifts across the range of an endemic tree species in a region experiencing an extreme drought.
We measured functional traits of 45 individuals of Kageneckia angustifolia from populations spanning its distribution in central Chile, along an abiotic stress gradient that decreases from the trailing to the leading edge. We identified individual-level ecological strategies using leaf and xylem traits and tested their association with tree growth, and we estimated statistical moments of intraspecific trait variation and multidimensional trait diversity across populations with bootstrapping.
We found that intraspecific trait variation of K. angustifolia was dominated by three ecological strategies: hydraulic safety and efficiency, resource use and water use. Across populations, tree growth was positively correlated with the hydraulic safety and efficiency ecological strategy, xylem traits and leaf thickness. Our results show that mean leaf traits shifted towards values associated with conservative resource use and xylem traits shifted towards values associated with hydraulic safety in the trailing edge. Likewise, variance decreased towards the trailing edge, skewness was positive for most traits, and kurtosis was largely negative. Consequently, multidimensional trait diversity decreased non-linearly towards the trailing edge.
Our results revealed that asymmetric environmental filtering shifted trait distributions and, therefore, lowered trait diversity of K. angustifolia, probably owing to increasing drought stress. Our results suggest that these shifts enable greater persistence of populations at the trailing edge, yet the long-term viability of the species is likely to depend on its capacity to disperse to sites with suitable abiotic conditions beyond its current distribution.
气候变化正在通过改变物种分布范围来改变生物多样性。然而，对于植物而言，这些分布变化背后的机制尚未得到充分理解，因为它们对降水或温度变化的反应往往具有独特性。在此，我们评估了生态策略是否介导树木生长，以及在经历极端干旱的地区，一个特有树种的种内性状多样性是否会在其分布范围内发生变化。
我们沿着从分布区后缘到前缘逐渐降低的非生物胁迫梯度，测量了智利中部卡赫内基亚窄叶树（Kageneckia angustifolia）分布区内45个个体的功能性状。我们利用叶片和木质部性状确定个体水平的生态策略，并测试它们与树木生长的关联，同时通过自助法估计种群内性状变异的统计矩和多维性状多样性。
我们发现，卡赫内基亚窄叶树的种内性状变异由三种生态策略主导：水力安全与效率、资源利用和水分利用。在各个种群中，树木生长与水力安全和效率生态策略、木质部性状及叶片厚度呈正相关。我们的结果表明，后缘的平均叶片性状向与保守资源利用相关的值转变，木质部性状则向与水力安全相关的值转变。同样，后缘的方差减小，大多数性状的偏度为正，峰度大多为负。因此，多维性状多样性后缘呈非线性下降。
我们的结果表明，不对称的环境筛选改变了性状分布，从而降低了卡赫内基亚窄叶树的性状多样性，这可能是由于干旱胁迫加剧所致。我们的结果表明，这些变化使后缘种群具有更强的持久性，但该物种的长期生存能力可能取决于其扩散到当前分布范围以外具有适宜非生物条件地点的能力。
