Gade Florian, Metz Johannes
Plant Ecology & Nature Conservation Group, Institute of Biology & Chemistry University of Hildesheim Hildesheim Germany.
Ecol Evol. 2024 Nov 10;14(11):e70513. doi: 10.1002/ece3.70513. eCollection 2024 Nov.
Competition in mesic sites and drought stress combined with short growing seasons in drier sites are key environmental factors along macroclimatic aridity gradients. They impose a triangular trade-off for local adaptation. However, as experiments have rarely disentangled their effects on plant fitness, uncertainty remained whether mesic populations are indeed better competitors and drier populations better adapted to drought stress and short season length. Aridity differs also at microclimatic scale between north (more mesic) and south (more arid) exposed hill-slopes. Little is known whether local adaptation occurs among exposures and whether south exposures harbor conspecifics better adapted to drier climates that could provide adaptive reservoirs under climate change. We sampled two Mediterranean annuals () in 15 sites along a macroclimatic aridity gradient (89-926 mm rainfall) on corresponding north and south exposures. In a large greenhouse experiment, we measured their fitness under drought stress, competition, and short vs. long growing seasons. Along the macroclimatic gradient, mesic populations were better competitors under benign conditions. Drier populations performed no better under drought stress per se but coped better with the short growing seasons typical for drier macroclimates. At microclimatic scale, north exposure plants were slightly better competitors in in , south exposure plants coped better with drought under short season length. We demonstrate that local adaptation to drier macroclimates is trading-off with competitive ability under benign conditions and vice-versa. Drought escape via short life-cycles was the primary adaptation to drier macroclimates, suggesting that intensified drought stress within the growing season under climate change challenges arid and mesic populations alike. Moreover, the drier microclimates at south exposures exhibited some potential as nearby reservoirs of drier-adapted genotypes. This potential needs further investigation, yet may assist populations to persist under climate change and lessen the need for long-distance migration.
中生境的竞争、干旱胁迫以及干旱地区较短的生长季节，这些都是沿宏观气候干旱梯度的关键环境因素。它们构成了一个关于局部适应的三角权衡关系。然而，由于实验很少能区分它们对植物适合度的影响，中生境种群是否确实是更好的竞争者，而干旱地区的种群是否更能适应干旱胁迫和较短的季节长度，仍然存在不确定性。在微气候尺度上，朝北（更湿润）和朝南（更干旱）的山坡之间干旱程度也有所不同。对于不同朝向之间是否发生局部适应，以及朝南的地方是否存在更能适应干旱气候的同种植物，而这些植物在气候变化下可能成为适应性储备，我们了解得很少。我们沿着宏观气候干旱梯度（降雨量89 - 926毫米）在15个地点对两种地中海一年生植物进行了采样，这些地点对应的有朝北和朝南的朝向。在一个大型温室实验中，我们测量了它们在干旱胁迫、竞争以及短生长季节与长生长季节条件下的适合度。沿着宏观气候梯度，中生境种群在良性条件下是更好的竞争者。干旱地区的种群本身在干旱胁迫下表现并不更好，但能更好地应对干旱地区典型的短生长季节。在微气候尺度上，在[具体条件1]下朝北朝向的植物是稍好的竞争者，在短季节长度下朝南朝向的植物更能应对干旱。我们证明，对更干旱宏观气候的局部适应与在良性条件下的竞争能力是相互权衡的，反之亦然。通过短生命周期实现的干旱逃避是对更干旱宏观气候的主要适应方式，这表明气候变化下生长季节内加剧的干旱胁迫对干旱地区和中生境的种群都构成了挑战。此外，朝南朝向更干旱微气候区域表现出作为适应干旱基因型的附近储备的一些潜力。这种潜力需要进一步研究，但可能有助于种群在气候变化下持续存在，并减少长距离迁移的需求。
