Rogers S M, Bernatchez L
Québec Océan, Département de Biologie, Université Laval, Ste-Foy, Québec, Canada.
Mol Biol Evol. 2007 Jun;24(6):1423-38. doi: 10.1093/molbev/msm066. Epub 2007 Apr 2.
Adaptive evolutionary change is contingent on variation and selection; thus, understanding adaptive divergence and ultimately speciation requires information on both the genetic basis of adaptive traits as well as an understanding of the role of divergent natural selection on those traits. The lake whitefish (Coregonus clupeaformis) consists of several sympatric "dwarf" (limnetic) and normal (benthic) species pairs that co-inhabit northern postglacial lakes. These young species pairs have evolved independently and display parallelism in life history, behavioral, and morphological divergence associated with the use of distinct trophic resources. We identified phenotype-environment associations and determined the genetic architecture and the role of selection modulating population genetic divergence in sympatric dwarf and normal lake whitefish. The genetic architecture of 9 adaptive traits was analyzed in 2 hybrid backcrosses individually phenotyped throughout their life history. Significant quantitative trait loci (QTL) were associated with swimming behavior (habitat selection and predator avoidance), growth rate, morphology (condition factor and gill rakers), and life history (onset of maturity and fecundity). Genome scans among 4 natural sympatric pairs, using loci segregating in the map, revealed a signature of selection for 24 loci. Loci exhibiting a signature of selection were associated with QTL relative to other regions of the genome more often than expected by chance alone. Two parallel QTL outliers for growth and condition factor exhibited segregation distortion in both mapping families, supporting the hypothesis that adaptive divergence contributing to parallel reductions of gene flow among natural populations may cause genetic incompatibilities. Overall, these findings offer evidence that the genetic architecture of ecological speciation is associated with signatures of selection in nature, providing strong support for the hypothesis that divergent natural selection is currently maintaining adaptive differentiation and promoting ecological speciation in lake whitefish species pairs.
适应性进化变化取决于变异和选择；因此，理解适应性分化以及最终的物种形成需要有关适应性性状的遗传基础的信息，以及对这些性状上分歧性自然选择作用的理解。湖白鲑（Coregonus clupeaformis）由几个同域分布的“矮型”（湖沼型）和正常（底栖型）物种对组成，它们共同栖息在北方的冰后期湖泊中。这些年轻的物种对独立进化，并在生活史、行为和形态分化方面表现出平行性，这些分化与不同营养资源的利用有关。我们确定了表型与环境的关联，并确定了同域分布的矮型和正常湖白鲑群体遗传分化的遗传结构以及选择的作用。在两个杂交回交群体中分析了9个适应性性状的遗传结构，这两个群体在其整个生活史中都进行了单独的表型分析。显著的数量性状位点（QTL）与游泳行为（栖息地选择和躲避捕食者）、生长速率、形态（体型因子和鳃耙）以及生活史（成熟起始和繁殖力）相关。利用在图谱中分离的位点对4个自然同域分布物种对进行全基因组扫描，发现了24个位点的选择信号。表现出选择信号的位点与QTL的关联比仅靠随机预期的情况更频繁地出现在基因组的其他区域。两个与生长和体型因子相关的平行QTL异常值在两个定位群体中都表现出分离畸变，支持了这样的假说，即导致自然种群间基因流平行减少的适应性分化可能会导致遗传不相容性。总体而言，这些发现提供了证据，表明生态物种形成的遗传结构与自然界中的选择信号相关，为以下假说提供了有力支持：分歧性自然选择目前正在维持湖白鲑物种对中的适应性分化并促进生态物种形成。
