Genomic diversity, population structure, and migration following rapid range expansion in the balsam poplar, Populus balsamifera

Rapid range expansions can cause pervasive changes in the genetic diversity and structure of populations. The post-glacial history of the Balsam Poplar, Populus balsamifera, involved the colonization of most of northern North America, an area largely covered by continental ice sheets during the last glacial maximum. To characterize how this expansion shaped genomic diversity within and among populations, we developed 412 SNP markers that we assayed for a range-wide sample of 474 individuals sampled from 34 populations. We complemented the SNP dataset with DNA sequence data from 11 nuclear loci from 94 individuals, and used coalescent analyses to estimate historical population size, demographic growth, and patterns of migration. Bayesian clustering identified three geographically separated demes found in the Northern, Central, and Eastern portions of the species range. These demes varied significantly in nucleotide diversity, the abundance of private polymorphisms, and population substr...快速的分布范围扩张会对种群的遗传多样性与群体遗传结构造成广泛影响。美洲脂杨（Populus balsamifera）的冰后演化历史涵盖了对北美北部绝大多数区域的拓殖——该区域在末次盛冰期曾被大陆冰盖大范围覆盖。为解析此次分布扩张如何塑造种群内外的基因组多样性，我们开发了412个单核苷酸多态性（Single Nucleotide Polymorphism, SNP）标记，并对采自34个种群、覆盖该物种全分布范围的474份个体样本开展了分型检测。我们辅以94份个体的11个核基因座DNA序列数据对SNP数据集进行补充，并通过溯祖分析估算了历史种群规模、种群增长模式以及基因流格局。贝叶斯聚类分析（Bayesian clustering）鉴定出该物种分布区北部、中部与东部存在三个地理隔离的居群。上述居群在核苷酸多样性、私有多态位点丰度以及种群亚结构（原文未完整展示）等方面均存在显著差异。