Footprints of divergent selection in natural populations of Castanopsis fargesii (Fagaceae)
Footprints of divergent selection in natural populations of Castanopsis fargesii (Fagaceae)
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角槠（壳斗科）自然种群发散选择的足迹
DOI：
10.1038/hdy.2014.58
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发表时间：
2014-12-01
期刊：
影响因子：
3.8
通讯作者：
Cannon, C. H.
中科院分区：
文献类型：
--
作者：
Li, C.;Sun, Y.;Cannon, C. H.
考虑到预计的快速气候变化，了解环境因素如何影响自然种群的遗传多样性是很重要的。未来的选择压力本质上是不可预测的，因此森林管理政策应既保持总体多样性，又确定与预计变化最快的环境因素（如温度和降雨）相关的遗传标记。本研究利用32表达序列标签（EST）衍生的微卫星标记对28个Castanopsis fargesii（壳壳科）居群中的648个个体进行了基因分型。在去除6个偏离Hardy-Weinberg平衡的位点后，我们测量了遗传变异、群体结构，并在温度和降水的选择下确定了候选位点。结果表明，该种群具有较高的遗传多样性，种群间分化程度适中，异交优势明显，对基因流动的限制较少。这些模式减少了随机效应或遗传隔离的可能影响。在四个位点上发现了分化选择的清晰足迹。这些位点的5个等位基因的频率与环境因子，特别是极端降水有很强的相关性。这些等位基因在梯度的一端几乎固定，在另一端则完全不存在。本研究树种是中国亚热带地区重要的森林树种，在未来的管理和再造林计划中具有重要作用。我们的研究结果表明，基因流在自然种群中广泛而丰富，保持了高度的多样性，而多样化选择作用于特定的基因组区域。
Given predicted rapid climate change, an understanding of how environmental factors affect genetic diversity in natural populations is important. Future selection pressures are inherently unpredictable, so forest management policies should maintain both overall diversity and identify genetic markers associated with the environmental factors expected to change most rapidly, like temperature and rainfall. In this study, we genotyped 648 individuals in 28 populations of Castanopsis fargesii (Fagaceae) using 32 expressed sequence tag (EST)-derived microsatellite markers. After removing six loci that departed from Hardy–Weinberg equilibrium, we measured genetic variation, population structure and identified candidate loci putatively under selection by temperature and precipitation. We found that C. fargesii populations possessed high genetic diversity and moderate differentiation among them, indicating predominant outcrossing and few restrictions to gene flow. These patterns reduce the possible impact of stochastic effects or the influence of genetic isolation. Clear footprints of divergent selection at four loci were discovered. Frequencies of five alleles at these loci were strongly correlated with environmental factors, particularly extremes in precipitation. These alleles varied from being near fixation at one end of the gradient to being completely absent at the other. Our study species is an important forest tree in the subtropical regions of China and could have a major role in future management and reforestation plans. Our results demonstrate that the gene flow is widespread and abundant in natural populations, maintaining high diversity, while diversifying selection is acting on specific genomic regions.