Kujala Sonja T, Avia Komlan, Kumpula Timo A, Kärkkäinen Hanni, Heikkinen Juha, Kärkkäinen Katri, Savolainen Outi
Natural Resources Institute Finland, Oulu, Finland.
University of Oulu, Ecology and Genetics, Oulu, Finland.
Evol Lett. 2023 Nov 27;8(2):231-242. doi: 10.1093/evlett/qrad054. eCollection 2024 Apr.
Parallel clines in traits related to adaptation in a species can be due to independent selection on a pair of traits, or due to selection in one trait resulting in a parallel cline in a correlated trait. To distinguish between the mechanisms giving rise to parallel adaptive population divergence of multiple traits along an environmental gradient we need to study variation, correlations, and selective forces within individual populations along the gradient. In many tree species, budset timing (BST) forms a latitudinal cline, and parallel clinal variation is also found in other seedling traits, such as first-year height (FYH) and fall frost injury (FFI). In this study, we set up a common garden experiment with open pollinated progeny from natural populations of Scots pine (), with one large sample from single population (500 families) and smaller samples from across a latitudinal gradient. BST, FYH and induced FFI were first measured in a greenhouse. The seedlings were then planted in the field, where survival and height were measured at the age of 9 years as fitness proxies. We compared between- and within-population variation and genetic correlations of these three seedling traits, and estimated selection gradients at the family level in our main population, taking into account the potential effects of seed weight. Between-population genetic correlations between seedling traits were high (0.76-0.95). Within-population genetic correlations in the main population were lower (0.14-0.35), as in other populations (0.10-0.39). Within population, extensive adaptive variation persists in the seedling traits, in line with rather weak selection gradients, yet maintaining the clines. Although our sampling does not cover the whole cline equally, the results suggest that the individual clines in these traits are maintained by largely independently acting selection, which results in fewer constraints in adaptation under changing climate.
一个物种中与适应相关的性状的平行渐变群可能是由于对一对性状的独立选择，或者是由于一个性状的选择导致相关性状出现平行渐变群。为了区分沿环境梯度导致多个性状平行适应性种群分化的机制，我们需要研究沿该梯度的各个种群内的变异、相关性和选择力。在许多树种中，芽形成时间（BST）形成了一个纬度渐变群，并且在其他幼苗性状中也发现了平行渐变变异，例如第一年树高（FYH）和秋季霜冻伤害（FFI）。在本研究中，我们用来自苏格兰松天然种群的开放授粉后代进行了一个共同园试验，从单个种群选取了一个大样本（500个家系），并从一个纬度梯度上选取了较小的样本。首先在温室中测量BST、FYH和诱导的FFI。然后将幼苗种植在田间，在9岁时测量其存活率和树高作为适合度指标。我们比较了这三个幼苗性状的种群间和种群内变异以及遗传相关性，并在考虑种子重量潜在影响的情况下，估计了我们主要种群中家系水平的选择梯度。幼苗性状之间的种群间遗传相关性较高（0.76 - 0.95）。主要种群内的种群内遗传相关性较低（0.14 - 0.35），其他种群也是如此（0.10 - 0.39）。在种群内，幼苗性状中存在广泛的适应性变异，这与相当弱的选择梯度一致，但仍维持着渐变群。尽管我们的采样并没有平等地覆盖整个渐变群，但结果表明这些性状中的各个渐变群在很大程度上是由独立起作用的选择维持的，这导致在气候变化下适应过程中的限制较少。
