Graduate Degree Program in Ecology, Department of BioAgricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, 80523-1177, USA; Apomixis Research Group, Institute for Plant Genetics and Crop Plant Improvement (IPK), Gatersleben, D-06466, Germany.
Mol Ecol. 2014 Sep;23(18):4486-97. doi: 10.1111/mec.12879. Epub 2014 Sep 3.
Determining the relative contribution of population genetic processes to the distribution of natural variation is a major goal of evolutionary biology. Here, we take advantage of variation in mating system to test the hypothesis that local adaptation is constrained by asexual reproduction. We explored patterns of variation in ecological traits and genome-wide molecular markers in Boechera spatifolia (Brassicaceae), a species that contains both apomictic (asexual) and sexual individuals. Using a combination of quantitative genetics, neutral genetic (SSR) and genome-wide single nucleotide polymorphism, we assessed the hypothesis that asexual lineages should have reduced signatures of adaptation relative to sexual conspecifics. All three measures (traits, SSRs, SNPs) demonstrated that apomicts are genetically distinct from sexuals, regardless of population location. Additionally, phylogenetic clustering revealed that the apomictic group shared a single common ancestor. Across the landscape, sexual genome-wide SNP variation was strongly associated with latitude (r(2) > 0.9), indicating that sexual populations have differentiated across an environmental gradient. Furthermore, flowering time and growth rate, as assessed in a common garden, strongly covary with the elevation and latitude of the source population. Despite a wide geographic distribution that largely overlaps with sexual populations, there was little evidence for differentiation in molecular markers or quantitative characters among apomictic populations. Combined, these data indicated that, in contrast to asexual populations, sexual populations show evidence of local adaptation.
确定种群遗传过程对自然变异分布的相对贡献是进化生物学的主要目标。在这里，我们利用交配系统的变异性来检验局部适应是否受到无性繁殖的限制这一假设。我们探索了 Boechera spatifolia（十字花科）生态特征和全基因组分子标记的变异模式，该物种包含无性（无性）和有性个体。我们采用了数量遗传学、中性遗传（SSR）和全基因组单核苷酸多态性相结合的方法，评估了无性系相对于有性同种个体适应能力降低的假设。所有三种方法（性状、SSR、SNP）都表明，无性系在遗传上与有性系不同，无论种群位置如何。此外，系统发育聚类表明，无性系群体共享一个单一的共同祖先。在整个景观中，性基因组 SNP 变异与纬度呈强正相关（r²＞0.9），表明性种群在环境梯度上已经分化。此外，在一个共同花园中评估的开花时间和生长率与来源种群的海拔和纬度强烈相关。尽管无性种群的地理分布范围广泛，与有性种群有很大的重叠，但在分子标记或数量特征方面，无性种群之间几乎没有分化的证据。综合这些数据表明，与无性种群相反，有性种群表现出局部适应的证据。
