Data from: Genetic architecture of sexual dimorphism in a subdioecious plant with a proto-sex chromosome

The rise of sexual dimorphism is thought to coincide with the evolution of sex chromosomes. Yet because sex chromosomes in many species are ancient, we lack empirical evidence of the earliest stages of this transition. We use QTL analysis to examine the genetic architecture of sexual dimorphism in subdioecious octoploid Fragaria virginiana. We demonstrate that the region housing the male-function locus controls the majority of quantitative variation in proportion fruit set, confirming the existence of a proto-sex chromosome, and houses major QTL for eight additional sexually dimorphic traits, consistent with theory and data from animals and plants with more advanced sex chromosomes. We also detected autosomal QTL, demonstrating contributions to phenotypic variation in sexually dimorphic traits outside the sex-determining region. Moreover, for proportion seed set we found significant epistatic interactions between autosomal QTL and the male-function locus, indicating sex-limited QTL. We identified linked QTL reflecting trade-offs between male and female traits expected from theory and positive integration of male traits. These findings indicate the potential for the evolution of greater sexual dimorphism. Involvement of linkage groups homeologous to the proto-sex chromosome in these correlations reflects the polyploid origin of F. virginiana and raises the possibility that chromosomes in this homeologous group were predisposed to become the sex chromosome.

性二态性（sexual dimorphism）的出现被认为与性染色体的演化同步。然而，由于诸多物种的性染色体均起源久远，我们尚缺乏该演化过渡早期阶段的实证证据。本研究采用数量性状基因座（Quantitative Trait Locus, QTL）分析方法，探究亚雌雄异株八倍体弗吉尼亚草莓（Fragaria virginiana）中性二态性的遗传架构。研究证实，携带雄性功能位点的基因组区域主导了坐果率比例的绝大多数数量变异，从而确认了原性染色体（proto-sex chromosome）的存在；该区域同时包含调控8个额外性二态性状的主效QTL，这与拥有更高级性染色体的动植物的相关理论及研究数据相符。本研究还检测到常染色体QTL，表明性别决定区域之外的性二态性状的表型变异同样受到其调控。此外，针对种子坐果率比例，我们发现常染色体QTL与雄性功能位点间存在显著的上位性互作，提示存在性别限制性QTL。我们还鉴定出连锁QTL，其反映了理论预期的雌雄性状间权衡关系，以及雄性性状间的正向整合。上述发现表明，该物种具备演化出更强性二态性的潜力。与原性染色体部分同源的连锁群参与上述相关性调控，这反映了弗吉尼亚草莓的多倍体起源，同时也提示该部分同源连锁群中的染色体原本就倾向于演化成为性染色体。