Quantitative genetic analysis indicates natural selection on leaf phenotypes across wild tomato species (Solanum sect. Lycopersicon; Solanaceae)

Adaptive evolution requires both raw genetic material and an accessible path of high fitness from one fitness peak to another. In this study, we used an introgression line (IL) population to map quantitative trait loci (QTL) for leaf traits thought to be associated with adaptation to precipitation in wild tomatoes (Solanum sect. Lycopersicon; Solanaceae). A QTL Sign Test showed that several traits likely evolved under directional natural selection. Leaf traits correlated across species do not share a common genetic basis, consistent with a scenario in which selection maintains trait covariation unconstrained by pleiotropy or linkage disequilibrium. Two large effect QTL for stomatal distribution colocalized with key genes in the stomatal development pathway, suggesting promising candidates for the molecular bases of adaptation in these species. Furthermore, macroevolutionary transitions between vastly different stomatal distributions may not be constrained when such large effect mutation...

适应性演化既需要原始遗传物质，也需要一条从一个适应度峰到另一个适应度峰的高适应度可及路径。本研究利用渐渗系（introgression line, IL）群体，对野生番茄（Solanum sect. Lycopersicon；茄科）中推测与降水适应相关的叶片性状的数量性状位点（quantitative trait loci, QTL）进行了定位。QTL符号检验（QTL Sign Test）结果显示，多个性状极有可能在定向自然选择作用下演化。跨物种间存在相关性的叶片性状并不共享共同的遗传基础，这与选择维持性状协变且不受多效性或连锁不平衡约束的情景相符。两个调控气孔分布的大效应QTL与气孔发育通路中的关键基因共定位，提示这些物种适应性演化的分子基础存在极具潜力的候选基因。此外，当存在此类大效应突变时，截然不同的气孔分布模式之间的宏演化过渡或许并不会受到约束。