Directional selection shifts trait distributions of planted species in dryland restoration

1. The match between species trait values and local abiotic filters can restrict community membership. An often-implicit assumption of this relationship is that abiotic filters select for a single locally optimal strategy, though difficulty in isolating effects of the abiotic environment from those of dispersal limitation and biotic interactions has resulted in few empirical tests of this assumption. Similar constraints have made it difficult to assess whether the type and intensity of abiotic filters shift along gradients of environmental harshness, as predicted by the stress dominance hypothesis.

2. We planted 9,216 plants of perennial grass and forb species that had a range of functional trait values and were assigned to a warm, intermediate, or cool temperature tolerance pools across eight sites on the Colorado Plateau. We compared the distributions of traits of surviving individuals to null distributions to evaluate whether there were shifts in trait means and variation. Borrowi...

1. 物种功能性状值（species trait values）与局域非生物过滤（local abiotic filters）的匹配关系，可限制群落成员构建（community membership）。该关联的一个普遍隐含假设为：非生物过滤会筛选得到单一的局域最优策略，但由于难以将非生物环境的效应与扩散限制（dispersal limitation）和生物相互作用（biotic interactions）的效应分离开来，目前针对该假设的实证检验寥寥无几。类似的研究限制也使得我们难以评估非生物过滤的类型与强度是否会沿环境严酷性梯度发生变化——这正是胁迫优势假说（stress dominance hypothesis）所预测的结论。
2. 我们在科罗拉多高原的8个样地内，种植了9216株具备多样功能性状值的多年生草本与非禾本草本植物，并将其划分为暖耐受、中耐受与冷耐受三类温度耐受功能群。我们将存活个体的性状分布与零分布（null distributions）进行对比，以评估性状均值与变异度是否发生了偏移。本研究借鉴……