Newman Dara, Pilson Diana
Division of Biological Sciences, University of Montana, Missoula, Montana, 59812.
School of Biological Sciences, 348 Manter Hall, University of Nebraska, Lincoln, Nebraska, 68588-0118.
Evolution. 1997 Apr;51(2):354-362. doi: 10.1111/j.1558-5646.1997.tb02422.x.
We established replicated experimental populations of the annual plant Clarkia pulchella to evaluate the existence of a causal relationship between loss of genetic variation and population survival probability. Two treatments differing in the relatedness of the founders, and thus in the genetic effective population size (N ), were maintained as isolated populations in a natural environment. After three generations, the low N treatment had significantly lower germination and survival rates than did the high N treatment. These lower germination and survival rates led to decreased mean fitness in the low N populations: estimated mean fitness in the low N populations was only 21% of the estimated mean fitness in the high N populations. This inbreeding depression led to a reduction in population survival: at the conclusion of the experiment, 75% of the high N populations were still extant, whereas only 31% of the low N populations had survived. Decreased genetic effective population size, which leads to both inbreeding and the loss of alleles by genetic drift, increased the probability of population extinction over that expected from demographic and environmental stochasticity alone. This demonstrates that the genetic effective population size can strongly affect the probability of population persistence.
我们建立了一年生植物美丽车轴草的重复实验种群，以评估遗传变异丧失与种群生存概率之间因果关系的存在。两种处理方式在奠基者的亲缘关系上存在差异，因而在遗传有效种群大小（N）上也有所不同，它们被作为隔离种群维持在自然环境中。三代之后，低N处理组的发芽率和存活率显著低于高N处理组。这些较低的发芽率和存活率导致低N种群的平均适合度下降：低N种群的估计平均适合度仅为高N种群估计平均适合度的21%。这种近交衰退导致种群生存能力降低：在实验结束时，75%的高N种群仍然存在，而低N种群中只有31%存活下来。遗传有效种群大小的降低，既导致了近亲繁殖，又因遗传漂变导致等位基因丧失，这增加了种群灭绝的概率，超过了仅由人口统计学和环境随机性所预期的概率。这表明遗传有效种群大小会强烈影响种群持续存在的概率。
