Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway.
Mol Ecol. 2014 Jun;23(11):2653-68. doi: 10.1111/mec.12770. Epub 2014 May 16.
Effective population size (N(e)) is a key parameter to understand evolutionary processes and the viability of endangered populations as it determines the rate of genetic drift and inbreeding. Low Ne can lead to inbreeding depression and reduced population adaptability. In this study, we estimated contemporary N(e) using genetic estimators (LDNE, ONeSAMP, MLNE and CoNe) as well as a demographic estimator in a natural insular house sparrow metapopulation. We investigated whether population characteristics (population size, sex ratio, immigration rate, variance in population size and population growth rate) explained variation within and among populations in the ratio of effective to census population size (N(e)/N(c)). In general, N(e)/N(c) ratios increased with immigration rates. Genetic N(e) was much larger than demographic N(e), probably due to a greater effect of immigration on genetic than demographic processes in local populations. Moreover, although estimates of genetic N(e) seemed to track N(c) quite well, the genetic N(e) -estimates were often larger than Nc within populations. Estimates of genetic N(e) for the metapopulation were however within the expected range (<N(c)). Our results suggest that in fragmented populations, even low levels of gene flow may have important consequences for the interpretation of genetic estimates of N(e). Consequently, further studies are needed to understand how N(e) estimated in local populations or the total metapopulation relates to actual rates of genetic drift and inbreeding.
有效种群大小 (N(e)) 是理解进化过程和濒危种群生存能力的关键参数，因为它决定了遗传漂变和近亲繁殖的速度。低 Ne 会导致近交衰退和种群适应能力降低。在这项研究中，我们使用遗传估算器 (LDNE、ONeSAMP、MLNE 和 CoNe) 以及人口统计学估算器在自然岛屿麻雀复合种群中估算了当代 N(e)。我们研究了种群特征（种群大小、性别比例、移民率、种群大小方差和种群增长率）是否解释了有效种群大小与种群大小之比 (N(e)/N(c)) 内和种群之间的变异。一般来说，N(e)/N(c) 比值随移民率的增加而增加。遗传 N(e) 远大于人口统计学 N(e)，这可能是由于移民对当地种群遗传过程的影响大于人口统计学过程。此外，尽管遗传 N(e) 的估计似乎很好地跟踪了 N(c)，但种群内的遗传 N(e) 估计通常大于 Nc。然而，复合种群的遗传 N(e) 估计值在预期范围内（<N(c)）。我们的研究结果表明，在碎片化的种群中，即使是低水平的基因流也可能对遗传 N(e) 的解释产生重要影响。因此，需要进一步的研究来了解如何将当地种群或整个复合种群的 N(e) 估计与实际遗传漂变和近亲繁殖的速度联系起来。
