Data from: Genome-wide scans reveal cryptic population structure in a dry-adapted eucalypt

Genome-wide DArTseq scans of 268 individuals of Eucalyptus salubris, distributed along an aridity gradient in southwestern Australia, revealed cryptic population structure that appears to signal hitherto unappreciated ecotypic differentiation and barriers to gene flow. Genome-wide scans were undertaken on 30 wild-sampled individuals from each of nine populations; 10 individuals per population were measured for habit and functional traits. DArTseq generated 16,122 high-quality markers, of which 56.3 % located to E. grandis chromosomes. Genetic affinities of the nine populations were only weakly correlated with geographic distances. Rather, populations appeared to form two distinct molecular lineages that maintained their distinctiveness in an area of geographic overlap. Twenty-four outlier markers signalled divergent selection and differentiation of the two putative lineages. Populations from the two lineages were phenotypically differentiated in leaf thickness, specific leaf area (SLA) and leaf nitrogen per unit mass (Nmass). The more northerly lineage (with thinner leaves) occurred in hotter, drier conditions with higher radiation. Populations of the more southerly lineage occurred on soils that were relatively low in phosphorus; the trees had thicker leaves, lower SLA and lower leaf Nmass, consistent with general responses to low nutrient levels. While historic isolation and drift may have contributed to the cryptic population structure observed, there is evidence of ecotypic adaptation, which may provide an exogenous barrier to gene flow. This study highlights the power of new molecular technologies to provide novel insights into the genetic architecture of wild populations.

对分布于澳大利亚西南部沿干旱梯度分布的268株亮果桉（Eucalyptus salubris）个体开展全基因组DArTseq扫描，结果揭示了隐秘的种群结构，该结构似乎预示着此前未被认知的生态型分化与基因流屏障。本研究从9个种群中各采集30株野生个体开展全基因组扫描，其中每个种群选取10株测定其生活型与功能性状。DArTseq共获得16122个高质量分子标记，其中56.3%的标记可定位至巨桉（E. grandis）染色体。9个种群的遗传亲缘关系与地理距离仅呈弱相关，与之相反，这些种群可划分为两个独立的分子谱系，且在地理重叠区域仍维持其遗传独特性。24个离群分子标记信号表明两个推定谱系间存在趋异选择与遗传分化。两个谱系的种群在叶厚度、比叶面积（specific leaf area, SLA）和单位质量叶氮含量（leaf nitrogen per unit mass, Nmass）上存在表型分化。分布更靠北的谱系（叶片更薄）栖息于辐射更强、更炎热干旱的生境；而分布更靠南的谱系的种群则生长于磷含量相对较低的土壤中，这类树木拥有更厚的叶片、更低的比叶面积与更低的单位质量叶氮含量，这与低养分条件下的典型响应特征一致。尽管历史隔离与遗传漂变可能促成了本次观测到的隐秘种群结构，但仍有证据表明存在生态型适应，这可能为基因流施加了外源屏障。本研究彰显了新兴分子技术的强大效力，可为解析野生种群的遗传架构提供全新视角。