Department of Molecular and Cell Biology, Energy Biosciences Institute, 545 Life Sciences Addition, University of California-Berkeley, Berkeley, CA 94720-3200, USA.
Mol Ecol. 2010 Jul;19(13):2739-53. doi: 10.1111/j.1365-294X.2010.04680.x. Epub 2010 Jun 7.
Local adaptation is considered to be the result of fitness trade-offs for particular phenotypes across different habitats. However, it is unclear whether such phenotypic trade-offs exist at the level of individual genetic loci. Local adaptation could arise from trade-offs of alternative alleles at individual loci or by complementary sets of loci with different fitness effects of alleles in one habitat but selective neutrality in the alternative habitat. To evaluate the genome-wide basis of local adaptation, we performed a field-based quantitative trait locus (QTL) mapping experiment on recombinant inbred lines (RILs) created from coastal perennial and inland annual races of the yellow monkeyflower (Mimulus guttatus) grown reciprocally in native parental habitats. Overall, we detected 19 QTLs affecting one or more of 16 traits measured in two environments, most of small effect. We identified 15 additional QTL effects at two previously identified candidate QTLs [DIVERGENCE (DIV)]. Significant QTL by environment interactions were detected at the DIV loci, which was largely attributable to genotypic differences at a single field site. We found no detectable evidence for trade-offs for any one component of fitness, although DIV2 showed a trade-off involving different fitness traits between sites, suggesting that local adaptation is largely controlled by non-overlapping loci. This is surprising for an outcrosser, implying that reduced gene flow prevents the evolution of individuals adapted to multiple environments. We also determined that native genotypes were not uniformly adaptive, possibly reflecting fixed mutational load in one of the populations.
局部适应被认为是不同生境中特定表型的适应性权衡的结果。然而，个体遗传基因座水平上是否存在这种表型权衡尚不清楚。局部适应可能源于个体基因座上替代等位基因的权衡，也可能源于具有不同等位基因适合度效应的互补基因座集合，在一个生境中具有选择中性，但在另一个生境中具有选择性。为了评估局部适应的全基因组基础，我们对来自沿海多年生和内陆一年生的黄色猴面花（Mimulus guttatus）重组自交系（RILs）进行了基于现场的数量性状基因座（QTL）作图实验，这些 RILs 在原生父母栖息地中相互生长。总体而言，我们检测到 19 个影响两个环境中 16 个测量性状之一或多个性状的 QTL，大多数 QTL 的效应较小。我们在两个先前鉴定的候选 QTL [DIVERGENCE (DIV)] 中鉴定了另外 15 个 QTL 效应。在 DIV 基因座上检测到 QTL 与环境的显著相互作用，这主要归因于单个现场的基因型差异。我们没有发现任何一个适合度成分的权衡的可检测证据，尽管 DIV2 显示了不同地点之间不同适合度特征的权衡，这表明局部适应主要由非重叠基因座控制。对于一个异交者来说，这令人惊讶，这意味着基因流的减少阻止了适应多个环境的个体的进化。我们还确定了本地基因型并非均匀适应，这可能反映了一个种群中的固定突变负荷。
