Heterostyly and self-incompatibility are usually controlled by the S locus complex, but the usually distylous Primula siebolodii shows continuous variation of anther and stigma position in some populations. Yoshida et al. make a genetic map of the species, and show that major QTLs for stigma and anther heights collocate with the S locus (accounting for 85% of the phenotypic variance). There are additional QTLs controlling anther height and corolla tube length, some being morph-specific. The markers were effective for investigating morph ratios in non-flowering populations, important as floral morphology is a target of selection and ratios differ between populations.
