Kalinowski Steven T, Waples Robin S
Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Boulevard East, Seattle, WA 98112, U.S.A.
Conserv Biol. 2002 Feb;16(1):129-136. doi: 10.1046/j.1523-1739.2002.00134.x.
The effective size of a population ( N ) rather than the census size ( N) determines its rate of genetic drift. Knowing the ratio of effective to census size, N / N, is useful for estimating the effective size of a population from census data and for examining how different ecological factors influence effective size. Two different multigenerational ratios have been used in the literature based on either the arithmetic mean or the harmonic mean in the denominator. We clarify the interpretation and meaning of these ratios. The arithmetic mean N / N ratio compares the total number of real individuals to the long-term effective size of the population. The harmonic mean N / N ratio summarizes variation in the N / N ratio for each generation. In addition, we show that the ratio of the harmonic mean population size to the arithmetic mean population size provides a useful measure of how much fluctuation in size reduced the effective size of a population. We discuss applications of these ratios and emphasize how to use the harmonic mean N / N ratio to estimate the effective size of a population over a period of time for which census counts have been collected.
种群的有效大小（Ne）而非普查大小（N）决定了其基因漂变速率。了解有效大小与普查大小的比率（Ne / N），对于根据普查数据估算种群的有效大小以及研究不同生态因素如何影响有效大小很有用。文献中基于分母中的算术平均数或调和平均数使用了两种不同的多代比率。我们阐明了这些比率的解释和含义。算术平均数Ne / N比率将实际个体总数与种群的长期有效大小进行比较。调和平均数Ne / N比率总结了每一代Ne / N比率的变化。此外，我们表明调和平均种群大小与算术平均种群大小的比率提供了一个有用的指标，用于衡量大小波动使种群有效大小降低了多少。我们讨论了这些比率的应用，并强调如何使用调和平均数Ne / N比率来估算在已收集普查计数的一段时间内种群的有效大小。
