Shrimpton J Mark, Heath Daniel D
Biology Program, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9.
Mol Ecol. 2003 Oct;12(10):2571-83. doi: 10.1046/j.1365-294x.2003.01932.x.
Population viability has often been assessed by census of reproducing adults. Recently this method has been called into question and estimation of the effective population size (Ne) proposed as a complementary method to determine population health. We examined genetic diversity in five populations of chinook salmon (Oncorhynchus tshawytscha) from the upper Fraser River watershed (British Columbia, Canada) at 11 microsatellite loci over 20 years using DNA extracted from archived scale samples. We tested for changes in genetic diversity, calculated the ratio of the number of alleles to the range in allele size to give the statistic M, calculated Ne from the temporal change in allele frequency, used the maximum likelihood method to calculate effective population size (NeM), calculated the harmonic mean of population size, and compared these statistics to annual census estimates. Over the last two decades population size has increased in all five populations of chinook examined; however, Ne calculated for each population was low (81-691) and decreasing over the time interval measured. Values of NeM were low, but substantially higher than Ne calculated using the temporal method. The calculated values for M were generally low (M < 0.70), indicating recent population reductions for all five populations. Large-scale historic barriers to migration and development activities do not appear to account for the low values of Ne; however, available spawning area is positively correlated with Ne. Both Ne and M estimates indicate that these populations are potentially susceptible to inbreeding effects and may lack the ability to respond adaptively to stochastic events. Our findings question the practice of relying exclusively on census estimates for interpreting population health and show the importance of determining genetic diversity within populations.
种群生存力通常通过对繁殖期成年个体的普查来评估。最近，这种方法受到了质疑，有效种群大小（Ne）的估计被提议作为确定种群健康状况的一种补充方法。我们使用从存档鳞片样本中提取的DNA，在20年时间里对来自加拿大不列颠哥伦比亚省弗雷泽河上游流域的五个奇努克鲑（Oncorhynchus tshawytscha）种群的11个微卫星位点的遗传多样性进行了研究。我们测试了遗传多样性的变化，计算了等位基因数量与等位基因大小范围的比值以得出统计量M，根据等位基因频率的时间变化计算Ne，使用最大似然法计算有效种群大小（NeM），计算种群大小的调和平均数，并将这些统计量与年度普查估计值进行比较。在过去二十年中，所研究的五个奇努克鲑种群的数量均有所增加；然而，为每个种群计算出的Ne较低（81 - 691），并且在所测量的时间间隔内呈下降趋势。NeM的值较低，但明显高于使用时间方法计算出的Ne。计算出的M值普遍较低（M < 0.70），表明所有五个种群近期数量都在减少。大规模的历史迁移障碍和开发活动似乎并不能解释Ne值较低的原因；然而，可用的产卵面积与Ne呈正相关。Ne和M的估计值均表明，这些种群可能易受近亲繁殖效应的影响，并且可能缺乏对随机事件进行适应性反应的能力。我们的研究结果对仅依靠普查估计来解释种群健康状况的做法提出了质疑，并表明了确定种群内遗传多样性的重要性。
