Kruse Stefan, Kolmogorov Aleksey I, Pestryakova Luidmila A, Herzschuh Ulrike
Polar Terrestrial Environmental Systems Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Potsdam Germany.
Institute of Natural Sciences North-Eastern Federal University of Yakutsk Yakutsk Russia.
Ecol Evol. 2020 Aug 17;10(18):10017-10030. doi: 10.1002/ece3.6660. eCollection 2020 Sep.
The occurrence of refugia beyond the arctic treeline and genetic adaptation therein play a crucial role of largely unknown effect size. While refugia have potential for rapidly colonizing the tundra under global warming, the taxa may be maladapted to the new environmental conditions. Understanding the genetic composition and age of refugia is thus crucial for predicting any migration response. Here, we genotype 194 larch individuals from an ~1.8 km area in northcentral Siberia on the southern Taimyr Peninsula by applying an assay of 16 nuclear microsatellite markers. For estimating the age of clonal individuals, we counted tree rings at sections along branches to establish a lateral growth rate that was then combined with geographic distance. Findings reveal that the predominant reproduction type is clonal (58.76%) by short distance spreading of ramets. One outlier of clones 1 km apart could have been dispersed by reindeer. In clonal groups and within individuals, we find that somatic mutations accumulate with geographic distance. Clonal groups of two or more individuals are observed. Clonal age estimates regularly suggest individuals as old as 2,200 years, which coincides with a major environmental change that forced a treeline retreat in the region. We conclude that individuals with clonal growth mode were naturally selected as it lowers the likely risk of extinction under a harsh environment. We discuss this legacy from the past that might now be a maladaptation and hinder expansion under currently strongly increasing temperatures.
北极树线以外避难所的出现以及其中的基因适应发挥着关键作用，但其效应大小在很大程度上未知。虽然避难所在全球变暖的情况下有可能迅速在冻原上定殖，但这些分类群可能无法适应新的环境条件。因此，了解避难所的基因组成和年代对于预测任何迁移反应至关重要。在这里，我们通过应用16个核微卫星标记的检测方法，对泰梅尔半岛南部西伯利亚中北部一个约1.8公里区域内的194株落叶松个体进行了基因分型。为了估计克隆个体的年龄，我们在树枝的横截面上计数年轮以确定横向生长速率，然后将其与地理距离相结合。研究结果表明，主要的繁殖类型是克隆繁殖（58.76%），通过分株的短距离传播实现。相距1公里的克隆中有一个异常值可能是由驯鹿传播的。在克隆群体和个体内部，我们发现体细胞突变随着地理距离的增加而积累。观察到两个或更多个体的克隆群体。克隆年龄估计通常表明个体年龄可达2200年，这与该地区树线被迫后退的一次重大环境变化相吻合。我们得出结论，具有克隆生长模式的个体是自然选择的结果，因为它降低了在恶劣环境下灭绝的可能性。我们讨论了这种过去遗留下来的情况，现在它可能是一种不适应，并且在当前温度急剧上升的情况下阻碍了扩张。
