Waples Robin S, Yokota Masashi
Northwest Fisheries Science Center, Seattle, Washington 98112, USA.
Genetics. 2007 Jan;175(1):219-33. doi: 10.1534/genetics.106.065300. Epub 2006 Nov 16.
The standard temporal method for estimating effective population size (N(e)) assumes that generations are discrete, but it is routinely applied to species with overlapping generations. We evaluated bias in the estimates N(e) caused by violation of this assumption, using simulated data for three model species: humans (type I survival), sparrow (type II), and barnacle (type III). We verify a previous proposal by Felsenstein that weighting individuals by reproductive value is the correct way to calculate parametric population allele frequencies, in which case the rate of change in age-structured populations conforms to that predicted by discrete-generation models. When the standard temporal method is applied to age-structured species, typical sampling regimes (sampling only newborns or adults; randomly sampling the entire population) do not yield properly weighted allele frequencies and result in biased N(e). The direction and magnitude of the bias are shown to depend on the sampling method and the species' life history. Results for populations that grow (or decline) at a constant rate paralleled those for populations of constant size. If sufficient demographic data are available and certain sampling restrictions are met, the Jorde-Ryman modification of the temporal method can be applied to any species with overlapping generations. Alternatively, spacing the temporal samples many generations apart maximizes the drift signal compared to sampling biases associated with age structure.
用于估计有效种群大小（N(e)）的标准时间方法假定世代是离散的，但它通常被应用于具有重叠世代的物种。我们使用三种模型物种（人类，I型生存；麻雀，II型；藤壶，III型）的模拟数据，评估了违反这一假设所导致的N(e)估计偏差。我们验证了费尔斯滕森之前的提议，即通过繁殖价值对个体进行加权是计算参数化种群等位基因频率的正确方法，在这种情况下，年龄结构种群的变化率符合离散世代模型的预测。当将标准时间方法应用于年龄结构物种时，典型的抽样方案（仅对新生儿或成体进行抽样；对整个种群进行随机抽样）不会产生加权适当的等位基因频率，并导致N(e)出现偏差。偏差的方向和大小取决于抽样方法和物种的生活史。以恒定速率增长（或下降）的种群的结果与大小恒定的种群的结果相似。如果有足够的人口统计学数据并满足某些抽样限制条件，时间方法的乔德 - 赖曼修正可应用于任何具有重叠世代的物种。或者，与与年龄结构相关的抽样偏差相比，将时间样本间隔许多代可以使漂变信号最大化。
