Pollen limitation, fruit abortion, and autonomous selfing in three populations of the perennial herb Ruellia nudiflora

Multiple factors determine plant reproductive success and their influence may vary spatially. This study addresses several factors influencing female reproductive success in three populations of Ruellia nudiflora, specifically we: (i) determine if fruit set is pollen-limited and if pollinator visitation rates are related to this condition; (ii) estimate fruit set via autonomous self-pollination (AS) and relate it to the magnitude of herkogamy; and (iii) evaluate if fruit abortion is a post-pollination mechanism that determines the magnitude of pollen limitation. At each site we marked 35 plants, grouped as: unmanipulated control (C) plants subjected to open pollination, plants manually cross-pollinated (MP), and plants excluded from pollinators and only able to self-pollinate autonomously (AS). Fruit set was greater for MP relative to C plants providing evidence for pollen limitation, while a tendency was observed for lower fruit abortion of MP relative to C plants suggesting that fruit set is influenced not only by pollen delivery per se, but also by subsequent abortion. In addition, although pollinator visits varied significantly among populations, the magnitude of pollen limitation did not, suggesting that pollinator activity was not relevant in determining pollen limitation. Finally, fruit set tended to decrease with the degree of herkogamy for AS plants, but this result was inconclusive. These findings have contributed to identify which factors influence reproductive success in populations of R.nudiflora, with potentially relevant implications for population genetic structure and mating system evolution of this species.