Verhoeven Koen J F, Vanhala Tytti K, Biere Arjen, Nevo Eviatar, van Damme Jos M M
Department of Plant Population Biology, Netherlands Institute of Ecology, NIOO-KNAW, PO Box 40, NL-6666 ZG, Heteren, The Netherlands.
Evolution. 2004 Feb;58(2):270-83.
We used a quantitative trait locus (QTL) approach to study the genetic basis of population differentiation in wild barley, Hordeum spontaneum. Several ecotypes are recognized in this model species, and population genetic studies and reciprocal transplant experiments have indicated the role of local adaptation in shaping population differences. We derived a mapping population from a cross between a coastal Mediterranean population and a steppe inland population from Israel and assessed F3 progeny fitness in the natural growing environments of the two parental populations. Dilution of the local gene pool, estimated as the proportion of native alleles at 96 marker loci in the recombinant lines, negatively affected fitness traits at both sites. QTLs for fitness traits tended to differ in the magnitude but not in the direction of their effects across sites, with beneficial alleles generally conferring a greater fitness advantage at their native site. Several QTLs showed fitness effects at one site only, but no opposite selection on individual QTLs was observed across the sites. In a common-garden experiment, we explored the hypothesis that the two populations have adapted to divergent nutrient availabilities. In the different nutrient environments of this experiment, but not under field conditions, fitness of the F3 progeny lines increased with the number of heterozygous marker loci. Comparison of QTL-effects that underlie genotype x nutrient interaction in the common-garden experiment and genotype x site interaction in the field suggested that population differentiation at the field sites may have been driven by divergent nutrient availabilities to a limited extent. Also in this experiment no QTLs were observed with opposite fitness effects in contrasting environments. Our data are consistent with the view that adaptive differentiation can be based on selection on multiple traits changing gradually along ecological gradients. This can occur without QTLs showing opposite fitness effects in the different environments, that is, in the absence of genetic trade-offs in performance between environments.
我们采用数量性状位点（QTL）方法来研究野生大麦（Hordeum spontaneum）群体分化的遗传基础。在这个模式物种中识别出了几种生态型，群体遗传学研究和互交移植实验表明了局部适应在塑造群体差异中的作用。我们从一个地中海沿岸群体与一个来自以色列的草原内陆群体的杂交中获得了一个定位群体，并在两个亲本群体的自然生长环境中评估了F3后代的适合度。局部基因库的稀释，以重组系中96个标记位点上本地等位基因的比例来估计，对两个地点的适合度性状都有负面影响。适合度性状的QTL在不同地点的效应大小上往往有所不同，但方向相同，有益等位基因通常在其本地位点赋予更大的适合度优势。几个QTL仅在一个地点显示出适合度效应，但在不同地点未观察到对单个QTL的反向选择。在一个共同园圃实验中，我们探讨了这两个群体已适应不同养分有效性的假设。在该实验的不同养分环境中，但不是在田间条件下，F3后代系的适合度随着杂合标记位点的数量增加而增加。共同园圃实验中基因型×养分相互作用和田间基因型×地点相互作用所基于的QTL效应比较表明，田间地点的群体分化可能在有限程度上是由不同的养分有效性驱动的。同样在这个实验中，在对比环境中未观察到具有相反适合度效应的QTL。我们的数据与这样一种观点一致，即适应性分化可以基于对沿着生态梯度逐渐变化的多个性状的选择。这可以在不同环境中不存在显示相反适合度效应的QTL的情况下发生，也就是说，在不同环境之间不存在性能上的遗传权衡。
