Department of Integrative Biology, University of Guelph, Guelph, 50 Stone Road West, ON, Canada, N1G 2W1.
Evol Dev. 2014 Jul-Aug;16(4):247-57. doi: 10.1111/ede.12087. Epub 2014 Jun 11.
The genetic variance that determines phenotypic variation can change across environments through developmental plasticity and in turn play a strong role in evolution. Induced changes in genotype-phenotype relationships should strongly influence adaptation by exposing different sets of heritable variation to selection under some conditions, while also hiding variation. Therefore, the heritable variation exposed or hidden from selection is likely to differ among habitats. We used ecomorphs from two divergent populations of Arctic charr (Salvelinus alpinus) to test the prediction that genotype-phenotype relationships would change in relation to environment. If present over several generations this should lead to divergence in genotype-phenotype relationships under common conditions, and to changes in the amount and type of hidden genetic variance that can evolve. We performed a common garden experiment whereby two ecomorphs from each of two Icelandic lakes were reared under conditions that mimicked benthic and limnetic prey to induce responses in craniofacial traits. Using microsatellite based genetic maps, we subsequently detected QTL related to these craniofacial traits. We found substantial changes in the number and type of QTL between diet treatments and evidence that novel diet treatments can in some cases provide a higher number of QTL. These findings suggest that selection on phenotypic variation, which is both genetically and environmentally determined, has shaped the genetic architecture of adaptive divergence in Arctic charr. However, while adaptive changes are occurring in the genome there also appears to be an accumulation of hidden genetic variation for loci not expressed in the contemporary environment.
决定表型变异的遗传方差可以通过发育可塑性在环境之间发生变化，并进而在进化中发挥重要作用。基因型-表型关系的诱导变化应该通过在某些条件下使不同的遗传变异组暴露于选择，同时隐藏变异，从而强烈影响适应。因此，可遗传的变异在选择下暴露或隐藏的可能性在不同的栖息地之间存在差异。我们使用来自两个不同北极鳕鱼（Salvelinus alpinus）种群的生态型来检验基因型-表型关系会随环境变化的预测。如果这种变化持续几代，这应该会导致在共同条件下的基因型-表型关系的分歧，并导致可进化的隐藏遗传方差的数量和类型发生变化。我们进行了一个共同的花园实验，其中每个冰岛湖的两个生态型在模仿底栖和浮游猎物的条件下进行饲养，以诱导颅面特征的反应。使用基于微卫星的遗传图谱，我们随后检测到与这些颅面特征相关的 QTL。我们发现饮食处理之间 QTL 的数量和类型发生了很大变化，并且有证据表明，新的饮食处理在某些情况下可以提供更多的 QTL。这些发现表明，对由遗传和环境决定的表型变异的选择塑造了北极鳕鱼适应性分歧的遗传结构。然而，尽管基因组中正在发生适应性变化，但在当代环境中未表达的基因座的隐藏遗传变异似乎也在积累。
