Davidson Bill E, Germino Matthew J
Forest and Rangeland Ecosystem Science Center U.S. Geological Survey Boise ID USA.
Ecol Evol. 2020 Aug 19;10(18):9920-9931. doi: 10.1002/ece3.6651. eCollection 2020 Sep.
Adaptive variation among plant populations must be known for effective conservation and restoration of imperiled species and predicting their responses to a changing climate. Common-garden experiments, in which plants sourced from geographically distant populations are grown together such that genetic differences may be expressed, have provided much insight on adaptive variation. Common-garden experiments also form the foundation for climate-based seed-transfer guidelines. However, the spatial scale at which population differentiation occurs is rarely addressed, leaving a critical information gap for parameterizing seed-transfer guidelines and assessing species' climate vulnerability. We asked whether adaptation was evident among populations of a foundational perennial within a single "empirical" seed-transfer zone (based on previous common-garden findings evaluating very distant populations) but different "provisional" seed zones (groupings of areas of similar climate and are not parameterized from common-garden data). Seedlings from three populations originating from similar conditions within an intermediate elevation were planted into gardens nearby at the same elevation, or 250-450 m higher or lower in elevation and 0.4-25 km away. Substantial variation was observed between gardens in survival (ranging 2%-99%), foliar crown volume (7.8-22.6 dm), and reproductive effort (0%-65%), but not among the three transplanted populations. The between garden variation was inversely related to climatic differences between the gardens and seed-source populations, specifically the site differences in maximum-minimum annual temperatures. Results suggest that substantial site-specificity in adaptation can occur at finer scales than is accounted for in empirical seed-transfer guidance when the guidance is derived from broadscale common-garden studies. Being within the same empirical seed zone, geographic unit, and even within 10 km distance may not qualify as "local" in the context of seed transfer. Moving forward, designing common-garden experiments so that they allow for testing the scale of adaptation will help in translating the resulting seed-transfer guidance to restoration projects.
为了有效地保护和恢复濒危物种并预测它们对气候变化的反应，必须了解植物种群之间的适应性变异。在共同花园实验中，将来自地理上遥远种群的植物种植在一起，以便能够表达遗传差异，这为适应性变异提供了很多见解。共同花园实验也构成了基于气候的种子转移指南的基础。然而，种群分化发生的空间尺度很少被涉及，这在参数化种子转移指南和评估物种的气候脆弱性方面留下了关键的信息空白。我们询问，在一个单一的“经验性”种子转移区域（基于先前对非常遥远种群进行评估的共同花园研究结果）内，但不同的“临时性”种子区域（气候相似区域的分组，且未根据共同花园数据进行参数化）中，一种基础多年生植物的种群之间是否存在明显的适应性。将来自中海拔地区相似条件下的三个种群的幼苗种植在附近相同海拔的花园中，或者种植在海拔高250 - 450米或低250 - 450米且距离为0.4 - 25公里的花园中。在不同花园中观察到了存活率（范围为2% - 99%）、叶冠体积（7.8 - 22.6立方分米）和繁殖努力（0% - 65%）的显著差异，但在三个移植种群之间没有观察到差异。花园之间的差异与花园和种子源种群之间的气候差异呈负相关，特别是年最高 - 最低温度的地点差异。结果表明，当经验性种子转移指南来自大规模共同花园研究时，适应性在比该指南所考虑的更精细尺度上可能存在显著的地点特异性。在种子转移的背景下，处于相同的经验性种子区域、地理单元甚至距离在10公里以内，可能都不能算作“本地”。展望未来，设计共同花园实验以便能够测试适应尺度，将有助于把由此产生的种子转移指南应用到恢复项目中。
