Data from: Transmission advantage favors selfing in experimental populations of self-incompatible Witheringia solanacea

The evolution of self-fertilization is one of the most commonly traversed transitions in flowering plants, with profound implications for population genetic structure and evolutionary potential. We investigated factors influencing this transition using Witheringia solanacea, a predominantly self-incompatible species within which self-compatible genotypes have been identified. We showed that self-compatibility in this species segregates with variation at the S-locus as inherited by plants in F1 and F2 generations. To examine reproductive assurance and the transmission advantage of selfing, we placed self-compatible and self-incompatible genotypes in genetically replicated gardens and monitored male and female reproductive success, as well as selfing rates of self-compatible plants. Self-compatibility did not lead to increased fruit or seed set, even under conditions of pollinator scarcity, and the realized selfing rate of self-compatible plants was less than 10%. Self-compatible plants had higher fruit abortion rates, consistent with previous evidence showing strong inbreeding depression at the embryonic stage. Although the selfing allele did not provide reproductive assurance under observed conditions, it also did not cause pollen discounting, so the transmission advantage of selfing should promote its spread. Given observed numbers of S-alleles and selfing rates, self-compatibility should spread even under conditions of exceedingly high initial inbreeding depression.