Baker Allan J
Department of Ornithology, Royal Ontario Museum, Toronto, ON, M5S 2C6, CANADA.
Department of Zoology, University of Toronto, Toronto, ON, M5S 1A1, CANADA.
Evolution. 1992 Dec;46(6):1784-1800. doi: 10.1111/j.1558-5646.1992.tb01169.x.
Descendent populations of chaffinches (Fringilla coelebs) introduced to New Zealand about 120 years ago were compared with "ancestral" populations in northern Europe and with those in a broader region of Europe (including Iberia) using protein electrophoresis at 42 loci and 12 skeletal measurements. The New Zealand populations exhibit very small scale differentiation in genetics (F = 0.040) and morphometrics, and the haphazard pattern of among-population variation does not align with environmental variation nor is it predicted by the geographic proximity of populations. Thus random drift is implicated in the differentiation among the descendent populations. The New Zealand chaffinches have diverged only slightly in morphometrics from an extant population in southern England, and constant heritability rate tests suggest that random drift alone could account for this small shift. In sharp contrast, the European populations are subdivided genetically (F = 0.222) and morphometrically, and this subdivision coincides with the Pyrenees mountains between Iberia and northern Europe which act as a barrier to gene flow between these regions. Iberian populations have smaller skulls and longer wings on average than northern European populations and are characterized by high frequencies of alternative common alleles at Ada and Np. Within both the Iberian and northern European regions, however, populations are effectively panmictic in protein-encoding genes, indicating that homogenizing gene flow is apparently extensive enough to prevent among-population differentiation in allozymes by drift. Variation in body size as represented by PC I is related to environmental productivity across Europe, unlike in New Zealand. These observations jointly suggest that longer term adaptive differentiation via selection for optimal body size has evolved in Europe. Because multilocus evolution is expected to proceed slowly in populations subject to the opposing forces of selection and homogenizing gene flow, I argue that local adaptation within "ancestral" populations in northern Europe may still be evolving.
大约120年前被引入新西兰的苍头燕雀（Fringilla coelebs）后代种群，与北欧的“祖先”种群以及欧洲更广泛地区（包括伊比利亚半岛）的种群进行了比较，比较方法是对42个基因座进行蛋白质电泳以及进行12项骨骼测量。新西兰的种群在遗传学（F = 0.040）和形态测量学上表现出非常小的分化，种群间变异的随机模式与环境变异不一致，也不能通过种群的地理距离来预测。因此，随机漂变与后代种群的分化有关。新西兰的苍头燕雀在形态测量学上与英格兰南部的现存种群仅有轻微差异，恒定遗传率测试表明，仅随机漂变就能解释这种小的变化。形成鲜明对比的是，欧洲的种群在基因（F = 0.222）和形态测量学上是细分的，这种细分与伊比利亚半岛和北欧之间的比利牛斯山脉相吻合，该山脉是这些地区之间基因流动 的障碍。伊比利亚半岛的种群平均头骨较小，翅膀较长，其特征是在Ada和Np位点上替代常见等位基因的频率较高。然而，在伊比利亚半岛和北欧地区内，种群在蛋白质编码基因方面实际上是随机交配的，这表明同质化的基因流动显然足够广泛，足以防止通过漂变在等位酶中出现种群间分化。与新西兰不同，以主成分I表示的体型变化与欧洲各地的环境生产力有关。这些观察结果共同表明，欧洲已经通过选择最优体型进化出了更长期的适应性分化。由于在受到选择和同质化基因流动的相反力量影响的种群中，多位点进化预计会进展缓慢，我认为北欧“祖先”种群中的局部适应性可能仍在进化。
