PDF(Pubmed)
Abstract：
Estimating effective population size (N e) is important for theoretical and practical applications in evolutionary biology and conservation. Nevertheless, estimates of N e in organisms with complex life-history traits remain scarce because of the challenges associated with estimation methods. Partially clonal plants capable of both vegetative (clonal) growth and sexual reproduction are a common group of organisms for which the discrepancy between the apparent number of individuals (ramets) and the number of genetic individuals (genets) can be striking, and it is unclear how this discrepancy relates to N e. In this study, we analysed two populations of the orchid Cypripedium calceolus to understand how the rate of clonal versus sexual reproduction affected N e. We genotyped >1000 ramets at microsatellite and SNP loci, and estimated contemporary N e with the linkage disequilibrium method, starting from the theoretical expectation that variance in reproductive success among individuals caused by clonal reproduction and by constraints on sexual reproduction would lower N e. We considered factors potentially affecting our estimates, including different marker types and sampling strategies, and the influence of pseudoreplication in genomic data sets on N e confidence intervals. The magnitude of N e/N ramets and N e/N genets ratios we provide may be used as reference points for other species with similar life-history traits. Our findings demonstrate that N e in partially clonal plants cannot be predicted based on the number of genets generated by sexual reproduction, because demographic changes over time can strongly influence N e. This is especially relevant in species of conservation concern in which population declines may not be detected by only ascertaining the number of genets.
摘要：
估计有效种群大小（Ne）对于进化生物学和保护中的理论和实际应用非常重要。然而，由于与估计方法相关的挑战，具有复杂生活史特征的生物体中Ne的估计仍然很少。能够营养（克隆）生长和有性生殖的部分克隆植物是一类常见的生物体，其个体（分株）的表观数量和遗传个体（基因组）的数量之间的差异可能是惊人的，目前还不清楚这种差异是如何与Ne相关的。在这项研究中，我们分析了兰花的两个种群，以了解克隆与有性生殖的比率如何影响Ne。我们在微卫星和SNP位点对>1000分株进行了基因分型，并用连锁不平衡方法估计当代Ne，从理论上的预期开始，克隆繁殖和有性生殖的限制引起的个体之间生殖成功的差异会降低Ne。我们考虑了可能影响我们估计的因素，包括不同的标记类型和采样策略，以及基因组数据集中伪复制对Ne置信区间的影响。我们提供的Ne/N分株的大小和Ne/N基因组比率可用作具有相似生活史特征的其他物种的参考点。我们的发现表明，部分克隆植物中的Ne不能根据有性生殖产生的基因组数量来预测，因为人口统计学随时间的变化会强烈影响Ne。这在保护关注的物种中尤其重要，在该物种中，仅通过确定基因组数量就无法检测到种群下降。
