Submitted to: Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 27, 2010
Publication Date: November 30, 2010
Citation: Spigler, R.B., Ashman, T., Lewers, K.S. 2010. Genetic architecture of sexual dimorphism in a subdioecious plant with a proto-sex chromosome. Evolution. 65(4):1114-1126.
Interpretive Summary: Scientists know little about how genes are organized in the modern strawberry. By studying wild relatives of the modern strawberry, we determined the locations of genes in the strawberry that influence male and female flower development and hence may be associated with strawberry fruit production. The distribution of these genes in strawberry will help scientists better understand strawberry evolution and come up with better ways to develop new improved strawberries.
Sexual dimorphism is thought to arise once sexually antagonistic genes accumulate on sex chromosomes early in their evolution. Yet because the earliest stages of sex chromosome evolution are elusive, we lack empirical evidence supporting this theory. In this study, we shed first light on the genetic architecture of sexual dimorphism in subdioecious octoploid Fragaria virginiana, a species with a purported proto-sex chromosome, using QTL analysis. Our results clearly show that the region housing the male-function locus not only controls quantitative variation in female function, confirming the existence of a proto-sex chromosome, but also houses major QTL for eight additional sexually dimorphic traits. Examination of the genetic architecture of previously described trait correlations revealed genetically-based trade-offs between male and female traits expected from theory and suggested few constraints to the evolution of greater sexual dimorphism. Repeated involvement of linkage groups homeologous to the proto-sex chromosome in these correlations highlights the polyploid nature of F. virginiana and points to the intriguing possibility that this homeologous group serves as a reproductive hub housing genes controlling primary and secondary sexual traits, thus predisposing one of the chromosomes to become a sex chromosome. Consequently, this system may provide an example of an alternate route to the evolution of sexual dimorphism and sex chromosomes.