Solé-Medina Aida, Heer Katrin, Opgenoorth Lars, Kaldewey Phillip, Danusevicius Darius, Notivol Eduardo, Robledo-Arnuncio Juan J, Ramírez-Valiente José A
Department of Forest Ecology & Genetics, INIA-CIFOR, Madrid, Spain.
Escuela Internacional de Doctorado, Universidad Rey Juan Carlos, Móstoles, Spain.
AoB Plants. 2020 May 25;12(3):plaa019. doi: 10.1093/aobpla/plaa019. eCollection 2020 Jun.
Given that the ecological niche of tree species is typically narrower for earlier life stages, intraspecific genetic variation at early fitness traits may greatly influence the adaptive response of tree populations to changing environmental conditions. In this study, we evaluated genetic variation in early fitness traits among 12 populations of from a wide latitudinal range in Europe (41-55°N). We first conducted a chamber experiment to test for population differences in germination and the effect of pre-chilling treatment on seed dormancy release. We then established three common gardens spread across the species latitudinal range in order to evaluate levels of quantitative genetic variation and genotype-by-environment interaction at different early life traits. Our results showed significant variation in chamber germination rates among populations (0-60 %), with southern populations exhibiting lower germination. Pre-chilling treatments did not generally improve germination success. Population seedling emergence rates in the field were correlated with chamber germination rates, though being an order of magnitude lower, with an average ranging from 0 to 1.3 % across gardens. Highly significant variation was found in field emergence rates among populations, and between seed-crop years within populations, but not among families within populations. Populations differed in seedling height, diameter, slenderness and budburst date, with significant among-family variation. Population latitude was positively associated with chamber germination rate and with seedling emergence rate in one of the central field sites. Overall, genetic, environmental and demographic factors seem to influence the observed high levels of variation in early fitness traits among populations. Our results suggest limited regeneration capacity for the study species under drier conditions, but further field trials with sufficient replication over environments and seed crops will improve our understanding of its vulnerability to climate change.
鉴于树种的生态位在早期生命阶段通常较窄，早期适合度性状的种内遗传变异可能极大地影响树木种群对不断变化的环境条件的适应性反应。在本研究中，我们评估了来自欧洲广泛纬度范围（北纬41 - 55°）的12个种群的早期适合度性状的遗传变异。我们首先进行了室内实验，以测试种群在发芽方面的差异以及预冷处理对种子休眠解除的影响。然后，我们在该物种的纬度范围内建立了三个共同花园，以评估不同早期生命性状的数量遗传变异水平和基因型与环境的相互作用。我们的结果表明，种群间室内发芽率存在显著差异（0 - 60%），南部种群的发芽率较低。预冷处理一般并未提高发芽成功率。田间种群的幼苗出土率与室内发芽率相关，尽管低了一个数量级，各花园的平均出土率在0到1.3%之间。在种群间以及种群内不同种子丰年之间，田间出土率存在极显著差异，但在种群内家系间不存在差异。种群在幼苗高度、直径、细长比和芽萌发日期方面存在差异，家系间存在显著变异。种群纬度与室内发芽率以及一个中部田间地点的幼苗出土率呈正相关。总体而言，遗传、环境和人口统计学因素似乎影响了观察到的该树种早期适合度性状的高水平变异。我们的结果表明，在较干燥条件下，该研究物种的更新能力有限，但在不同环境和种子丰年进行充分重复的进一步田间试验将增进我们对其气候变化脆弱性的理解。
