Rowe Graham, Beebee Trevor J C
School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom.
Evolution. 2003 Jan;57(1):177-81. doi: 10.1111/j.0014-3820.2003.tb00228.x.
The fitness costs of high genetic load in wild populations have rarely been assessed under natural conditions. Such costs are expected to be greatest in small, bottlenecked populations, including those occurring near range edges. Britain is at the northwesterly range limit of the natterjack toad Bufo calamita. We compared fitness attributes in two populations of this amphibian with very different recent histories. Key larval fitness attributes in B. calamita, notably growth rate and metamorph production, were substantially higher in the large outbreeding population (Ainsdale) than in the small and isolated one (Saltfleetby). These differences were manifest under seminatural conditions, when larvae were reared in mesh cages within breeding ponds at the site of the small population, and were exacerbated by high stress treatments. The results indicate that genetic load effects can be sufficiently severe enough to predispose extinction over relatively short time frames, as predicted by extinction vortex models.
在自然条件下，野生种群中高遗传负荷的适合度代价很少得到评估。预计在小型瓶颈种群中，包括那些分布在分布范围边缘附近的种群，这种代价最大。英国位于黄条蟾蜍（Bufo calamita）分布范围的西北边界。我们比较了这种两栖动物两个近期历史截然不同的种群的适合度属性。在大型远交种群（安斯代尔）中，黄条蟾蜍关键的幼体适合度属性，尤其是生长速率和变态个体产量，显著高于小型孤立种群（索尔特弗利比）。当在小型种群所在地的繁殖池塘内的网箱中饲养幼体时，这些差异在半自然条件下就很明显，并且在高应激处理下会加剧。结果表明，正如灭绝漩涡模型所预测的那样，遗传负荷效应可能足够严重，足以在相对较短的时间框架内使种群易灭绝。
