School of Forestry, Northern Arizona University, Flagstaff, AZ, USA.
Instituto de Biología, Universidad Nacional Autónoma de México, Ciudad de México, México.
BMC Ecol Evol. 2024 Sep 3;24(1):117. doi: 10.1186/s12862-024-02304-4.
Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plays a critical role in the ecology and economy of Western North America. This conifer species comprises two distinct varieties: the coastal variety (var. menziesii) along the Pacific coast, and the interior variety (var. glauca) spanning the Rocky Mountains into Mexico, with instances of inter-varietal hybridization in Washington and British Columbia. Recent investigations have focused on assessing environmental pressures shaping Douglas-fir's genomic variation for a better understanding of its evolutionary and adaptive responses. Here, we characterize range-wide population structure, estimate inter-varietal hybridization levels, identify candidate loci for climate adaptation, and forecast shifts in species and variety distribution under future climates.
Using a custom SNP-array, we genotyped 540 trees revealing four distinct clusters with asymmetric admixture patterns in the hybridization zone. Higher genetic diversity observed in coastal and hybrid populations contrasts with lower diversity in inland populations of the southern Rockies and Mexico, exhibiting a significant isolation by distance pattern, with less marked but still significant isolation by environment. For both varieties, we identified candidate loci associated with local adaptation, with hundreds of genes linked to processes such as stimulus response, reactions to chemical compounds, and metabolic functions. Ecological niche modeling revealed contrasting potential distribution shifts among the varieties in the coming decades, with interior populations projected to lose habitat and become more vulnerable, while coastal populations are expected to gain suitable areas.
Overall, our findings provide crucial insights into the population structure and adaptive potential of Douglas-fir, with the coastal variety being the most likely to preserve its evolutionary path throughout the present century, which carry implications for the conservation and management of this species across their range.
花旗松（Pseudotsuga menziesii [Mirb.] Franco）在北美西部的生态和经济中起着至关重要的作用。这种针叶树种由两个截然不同的变种组成：太平洋沿岸的沿海变种（var. menziesii）和跨越落基山脉延伸到墨西哥的内陆变种（var. glauca），在华盛顿州和不列颠哥伦比亚省存在着变种间杂交的情况。最近的研究集中在评估塑造花旗松基因组变异的环境压力，以更好地了解其进化和适应反应。在这里，我们描述了广泛的种群结构，估计了变种间杂交的水平，确定了候选的适应气候的基因座，并预测了未来气候下物种和变种分布的变化。
使用定制的 SNP 芯片，我们对 540 棵树进行了基因分型，揭示了四个不同的聚类，在杂交区有不对称的杂种形成模式。沿海和杂种群体中观察到的更高遗传多样性与落矶山脉南部和墨西哥内陆群体中的较低多样性形成对比，表现出显著的距离隔离模式，环境隔离的程度虽然较小，但仍然显著。对于这两个变种，我们确定了与局部适应相关的候选基因座，有数百个基因与刺激反应、对化合物的反应以及代谢功能等过程有关。生态位建模揭示了在未来几十年中品种之间潜在分布的变化趋势不同，内陆种群预计会失去栖息地并变得更加脆弱，而沿海种群预计会获得适宜的区域。
总的来说，我们的研究结果提供了对花旗松种群结构和适应潜力的重要见解，沿海变种最有可能在本世纪内保持其进化轨迹，这对该物种在其分布范围内的保护和管理具有重要意义。
