Figure 1.

Evolution of S. latifolia PAR, showing the origins of the PAR boundary genes studied in this paper (simplified from Figure 4 of Qiu et al. (2016), and including gene locations only for these PAR boundary genes). (a) The ancestral state before the translocation events had a sex chromosome with a PAR (green region) and a region that had stopped recombining (black region, but not as separate X-linked and male-specific, or MSY, regions; different strata are not indicated in this diagram, but the black line includes all fully sex-linked regions). The two autosomes that later became translocated, moving the whole or part of these chromosome arms onto the PAR of the ancestral sex chromosome, are represented as pink and blue lines. The first and second translocation events are represented in (b and c), with different tones (or colours) indicating the linkage groups in S. vulgaris that carry the PAR boundary genes, when this is known. The cs4991 gene is not indicated because it could not be mapped in our S. vulgaris family; however, its location in the genetic map of the S. latifolia X chromosome is among the more distal genes added in the second translocation event. Other genes added in both translocations have remained loosely linked to the MSY boundary, and are not shown in the diagram. A full color version of this figure is available at the Heredity journal online.