Faculty of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland.
Icelandic Institute of Natural History, Akureyri, Iceland.
J Hered. 2023 Apr 6;114(2):165-174. doi: 10.1093/jhered/esac062.
Betula pubescens Ehrh. (mountain birch) is the only forest-forming tree in Iceland. Since human settlement (874 AD), the continuous 25,000 to 30,000 km2 forest has shrunk to 1.200 km2 of fragmented patches, making it a good object to study population genetic consequences of habitat fragmentation and disturbance. Further, genetic studies have also shown that hybridization between the tetraploid (2n = 56) B. pubescens and the diploid (2n = 28) Betula nana L. (dwarf birch) occurs among Iceland's natural populations. This study assessed the genetic variation within and among 11 birch forests remaining across Iceland. Genotype-by-sequencing methodology provided a total of 24,585 single nucleotide polymorphisms (SNP´s), with a minor allele frequency >5% for genetic analyses. The analysis showed similar diversity within forests, suggesting that fragmentation and hybridization have had a limited effect on the genetic variation within sites. A clear genetic divergence is found among forests from the different regions of Iceland that may reflect historical isolation; the differentiation between forests increased with geographic distances reflecting isolation by distance. Information on the distribution of genetic variation of birch in Iceland is essential for its conservation and to establish genotype-phenotype associations to predict responses to new environmental conditions imposed by climate change and novel biotic/abiotic stressors.
欧洲白桦（Betula pubescens Ehrh.）是冰岛唯一的成林树种。自人类定居（公元 874 年）以来，连续的 25000 至 30000 平方公里的森林已经缩小到 1200 平方公里的碎片斑块，这使其成为研究栖息地破碎化和干扰对种群遗传后果的理想对象。此外，遗传研究还表明，四倍体（2n = 56）欧洲白桦和二倍体（2n = 28）矮桦（Betula nana L.）之间发生了杂交。本研究评估了冰岛 11 个剩余桦树林内和之间的遗传变异。基于测序的基因型方法共提供了 24585 个单核苷酸多态性（SNP），其中遗传分析的次要等位基因频率> 5%。分析表明，森林内的多样性相似，表明破碎化和杂交对位点内的遗传变异影响有限。来自冰岛不同地区的森林之间存在明显的遗传差异，这可能反映了历史隔离；森林之间的分化随着地理距离的增加而增加，这反映了隔离距离的影响。了解桦树在冰岛的遗传变异分布信息对于其保护以及建立基因型-表型关联以预测对气候变化和新生物/非生物胁迫施加的新环境条件的响应至关重要。
