Poulsen Nina A A, Nielsen Einar E, Schierup Mikkel H, Loeschcke Volker, Grønkjaer Peter
Department of Inland Fisheries, Danish Institute for Fisheries Research, DK-8600 Silkeborg, Denmark.
Mol Ecol. 2006 Feb;15(2):321-31. doi: 10.1111/j.1365-294X.2005.02777.x.
DNA from archived otoliths was used to explore the temporal stability of the genetic composition of two cod populations, the Moray Firth (North Sea) sampled in 1965 and 2002, and the Bornholm Basin (Baltic Sea) sampled in 1928 and 1997. We found no significant changes in the allele frequencies for the Moray Firth population, while subtle but significant genetic changes over time were detected for the Bornholm Basin population. Estimates of the effective population size (Ne) generally exceeded 500 for both populations when employing a number of varieties of the temporal genetic method. However, confidence intervals were very wide and Ne's most likely range in the thousands. There was no apparent loss of genetic variability and no evidence of a genetic bottleneck for either of the populations. Calculations of the expected levels of genetic variability under different scenarios of Ne showed that the number of alleles commonly reported at microsatellite loci in Atlantic cod is best explained by Ne's exceeding thousand. Recent fishery-induced bottlenecks can, however, not be ruled out as an explanation for the apparent discrepancy between high levels of variability and recently reported estimates of Ne << 1000. From life history traits and estimates of survival rates in the wild, we evaluate the compatibility of the species' biology and extremely low Ne/N ratios. Our data suggest that very small Ne's are not likely to be of general concern for cod populations and, accordingly, most populations do not face any severe threat of losing evolutionary potential due to genetic drift.
利用存档耳石中的DNA来探究两个鳕鱼种群遗传组成的时间稳定性，这两个种群分别是1965年和2002年在莫雷湾（北海）采样的种群，以及1928年和1997年在博恩霍尔姆盆地（波罗的海）采样的种群。我们发现莫雷湾种群的等位基因频率没有显著变化，而博恩霍尔姆盆地种群随时间出现了细微但显著的遗传变化。当采用多种时间遗传方法时，两个种群的有效种群大小（Ne）估计值通常都超过了500。然而，置信区间非常宽，Ne最可能的范围在数千。两个种群均未出现明显的遗传变异性丧失，也没有遗传瓶颈的证据。在不同Ne情景下对遗传变异性预期水平的计算表明，大西洋鳕鱼微卫星位点通常报告的等位基因数量最好由超过一千的Ne来解释。然而，最近渔业导致的瓶颈不能排除作为变异性高水平与最近报告的Ne << 1000估计值之间明显差异的一种解释。根据生活史特征和野生种群存活率估计，我们评估了该物种生物学特性与极低的Ne/N比率之间的兼容性。我们的数据表明，非常小的Ne对鳕鱼种群不太可能普遍构成问题，因此，大多数种群不会因遗传漂变而面临丧失进化潜力的严重威胁。
