Data from: Mapping QTL contributing to variation in posterior lobe morphology between strains of Drosophila melanogaster

Closely-related, and otherwise morphologically similar insect species frequently show striking divergence in the shape and/or size of male genital structures, a phenomenon thought to be driven by sexual selection. Comparative interspecific studies can help elucidate the evolutionary forces acting on genital structures to drive this rapid differentiation. However, genetic dissection of sexual trait divergence between species is frequently hampered by the difficulty generating interspecific recombinants. Intraspecific variation can be leveraged to investigate the genetics of rapidly-evolving sexual traits, and here we carry out a genetic analysis of variation in the posterior lobe within D. melanogaster. The lobe is a male-specific process emerging from the genital arch of D. melanogaster and three closely-related species, is essential for copulation, and shows radical divergence in form across species. There is also abundant variation within species in the shape and size of the lobe, and while this variation is considerably more subtle than that seen among species, it nonetheless provides the raw material for QTL mapping. We created an advanced intercross population from a pair of phenotypically-different inbred strains, and after phenotyping and genotyping-by-sequencing the recombinants, mapped several QTL contributing to various measures of lobe morphology. The additional generations of crossing over in our mapping population led to QTL intervals that are smaller than is typical for an F2 mapping design. The intervals we map overlap with a pair of lobe QTL we previously identified in an independent mapping cross, potentially suggesting a level of shared genetic control of trait variation. Our QTL additionally implicate a suite of genes that have been shown to contribute to the development of the posterior lobe. These loci are strong candidates to harbor naturally-segregating sites contributing to phenotypic variation within D. melanogaster, and may also be those contributing to divergence in lobe morphology between species.

亲缘关系相近且形态学整体相似的昆虫物种，其雄性生殖器结构的形状和/或尺寸往往存在显著分化，这一现象被认为是由性选择（sexual selection）驱动的。跨物种比较研究有助于阐明作用于生殖器结构、推动这一快速分化的进化力量。然而，对物种间性性状分化进行遗传解析，往往因难以获得种间重组体而受阻。种内变异可被用于研究快速演化的性性状的遗传基础，本研究对黑腹果蝇（Drosophila melanogaster）的后叶（posterior lobe）变异开展了遗传分析。该后叶是从黑腹果蝇及其三种近缘物种的生殖弓（genital arch）中伸出的雄性特异性结构，对交配至关重要，且在不同物种间呈现出显著的形态分化。该物种内部的后叶形状与尺寸也存在丰富的变异，尽管这类变异远较物种间的变异更为细微，但仍为数量性状位点（quantitative trait locus, QTL）定位提供了基础材料。我们从一对表型存在差异的近交品系构建了高级互交群体，对重组体进行表型分型和基于测序的基因分型（genotyping-by-sequencing）后，定位了多个与后叶形态多项指标相关的数量性状位点。本研究的定位群体经过多代重组交换，使得定位得到的数量性状位点区间较典型的F2代（F2）定位设计更小。我们定位得到的区间与此前在独立定位杂交中发现的两个后叶数量性状位点存在重叠，这提示该性状变异可能存在一定程度的共享遗传调控机制。本研究定位的数量性状位点还关联到一系列已被证实参与后叶发育的基因。这些基因座极有可能携带导致黑腹果蝇种内表型变异的天然分离位点，同时也可能是推动物种间后叶形态分化的遗传基础。