Decay of self-incompatibility within a lifespan in Physalis acutifolia (Solanaceae)

Self-incompatibility decays with age in plants of Physalis acutifolia, and plants that have transitioned to selfing produce fewer seeds but with comparable viability. Self-compatibility in this system is closely related to flower size, which is in turn dependent on the direction of the cross, suggesting parental effects on both morphology and compatibility. The sharpleaf groundcherry, Physalis acutifolia, is polymorphic for self-compatibility, with naturally occurring self-incompatible (SI) and self-compatible (SC) populations. Moreover, SI individuals have been documented to transition to SC with age, at least in greenhouse conditions. Here we tested whether this within-lifespan transition occurs predictably (developmental decay of SI) or could result from a lack of pollination (a plastic response). Using greenhouse crosses, we demonstrated that SI P. acutifolia plants transition to SC after 70 days, regardless of pollination treatment, consistent with predictable developmental decay. This loss of SI corresponds to a loss of pollen inhibition, with self-pollen often reaching the ovary after 24 h. The originally SI plants that transition to SC can produce viable seeds from self crosses, albeit significantly fewer than from outcrosses of SI plants or from lines fixed for SC. Throughout the experiment, we observed that flower size, which differs between SI and SC populations, was highly correlated with the compatibility phenotype. These findings suggest that the mechanisms leading to the loss of SI during a lifespan are similar to those involved in fixed losses of SI, but that older plants that transition to SC do not present the same reproductive capacity as fixed selfers.