Per-gene synonymous divergence and respective standard error (dS ± SE) between alleles associated to the a1b1-a2b2 mating types along the mating-type chromosomes within diploid M. lagerheimii and M. saponariae individuals. Synonymous divergence is plotted against the genomic coordinates of the a1 b1 mating-type chromosomes of M. intermedium for all single-copy genes shared by the mating-type chromosomes, as a proxy for ancestral gene order. Divergence between the a1 and a2 pheromone receptor (PR) was too extensive (Devier et al. 2009) and could not be computed (noted as unalignable [UN]). The positions of the centromeres are indicated by yellow dots. Genes with dS > 0 between mating types around the PR and HD mating-type loci in M. lagerheimii are in purple and blue, respectively. The purple and blue regions correspond to the older PR and HD regions of suppressed recombination that evolved before and at the base of the radiation of the clade, respectively (Branco et al. 2017, 2018). Red arrows indicate the genes used for dating recombination cessation events. (A) Per-gene synonymous divergence between mating types in M. lagerheimii along the gene order of the a2 PR M. intermedium mating-type chromosome. (B) Per-gene synonymous divergence between mating types in M. lagerheimii along the gene order of the b2 HD M. intermedium mating-type chromosome. (C) Per-gene synonymous divergence between mating types in M. saponariae along the gene order of the a2 PR M. intermedium mating-type chromosome. (D) Per-gene synonymous divergence between mating types in M. saponariae along the gene order of the b2 HD M. intermedium mating-type chromosome.
