Palo J U, O'Hara R B, Laugen A T, Laurila A, Primmer C R, Merilä J
Ecological Genetics Research Unit, Department of Ecology and Systematics, PO Box 65, FIN-00014 University of Helsinki, Finland.
Mol Ecol. 2003 Jul;12(7):1963-78. doi: 10.1046/j.1365-294x.2003.01865.x.
The relative roles of natural selection and direct environmental induction, as well as of natural selection and genetic drift, in creating clinal latitudinal variation in quantitative traits have seldom been assessed in vertebrates. To address these issues, we compared molecular and quantitative genetic differentiation between six common frog (Rana temporaria) populations along an approximately 1600 km long latitudinal gradient across Scandinavia. The degree of population differentiation (QST approximately 0.81) in three heritable quantitative traits (age and size at metamorphosis, growth rate) exceeded that in eight (neutral) microsatellite loci (FST = 0.24). Isolation by distance was clear for both neutral markers and quantitative traits, but considerably stronger for one of the three quantitative traits than for neutral markers. QST estimates obtained using animals subjected to different rearing conditions (temperature and food treatments) revealed some environmental dependency in patterns of population divergence in quantitative traits, but in general, these effects were weak in comparison to overall patterns. Pairwise comparisons of FST and QST estimates across populations and treatments revealed that the degree of quantitative trait differentiation was not generally predictable from knowledge of that in molecular markers. In fact, both positive and negative correlations were observed depending on conditions where the quantitative genetic variability had been measured. All in all, the results suggest a very high degree of genetic subdivision both in neutral marker genes and genes coding quantitative traits across a relatively recently (< 9000 years) colonized environmental gradient. In particular, they give evidence for natural selection being the primary agent behind the observed latitudinal differentiation in quantitative traits.
在脊椎动物中，很少评估自然选择与直接环境诱导以及自然选择与遗传漂变在造成数量性状的渐变纬度变异方面的相对作用。为了解决这些问题，我们比较了斯堪的纳维亚半岛上沿大约1600公里长的纬度梯度分布的六个普通青蛙（林蛙）种群之间的分子和数量遗传分化。三个可遗传数量性状（变态时的年龄和大小、生长速率）的种群分化程度（QST约为0.81）超过了八个（中性）微卫星位点的分化程度（FST = 0.24）。中性标记和数量性状都存在明显的距离隔离现象，但三个数量性状之一的距离隔离比中性标记要强得多。对处于不同饲养条件（温度和食物处理）下的动物进行QST估计，结果显示数量性状的种群分化模式存在一定的环境依赖性，但总体而言，与整体模式相比，这些影响较弱。对不同种群和处理下的FST和QST估计进行成对比较，结果表明，从分子标记的分化程度通常无法预测数量性状的分化程度。事实上，根据测量数量遗传变异的条件，观察到了正相关和负相关。总而言之，结果表明在一个相对较新（<9000年）殖民的环境梯度中，中性标记基因和编码数量性状的基因都存在非常高程度的遗传细分。特别是，它们为自然选择是观察到的数量性状纬度分化背后的主要因素提供了证据。
