Self-incompatibility in Habranthus gracilifolius (Amaryllidaceae): pre- and post-pollination barriers

Abstract

The evolution of self-incompatibility seems to be responsible for a great part of the evolutionary success of flowering plants by preventing self-fertilization and, hence, the effects of inbreeding. The recognition of incompatibility mechanisms allows us to explore their emergency and functionality and is particularly interesting in hermaphrodite plants due to the sexual conflict they experience. Here, we investigated some pre- and post-pollination barriers for self-reproduction in Habranthus gracilifolius Herb. In a natural population, we performed hand pollinations to check mating and incompatibility systems, measured the distance between anthers and stigma within flowers, and observed flower visitors. Our results evidence that this species is self-incompatible and reproduces via outcrossing (90% of crossed flowers set fruits). Self-pollen grains germinate on the stigma surface and are stopped at the beginning of the style, typical of gametophytic self-incompatibility. The species presents approach herkogamy–stigma is positioned in average 2.78 mm above stamens, which may reduce pollen self-interference. It is visited by a variety of insects, many acting as thieves. Our indirect measures of pollinator performance suggest that flower visitation frequency alone is not enough to evaluate visitors’ effects on fruit set. Herkogamy and gametophytic self-incompatibility prevent self-pollination and self-fertilization, respectively, and together with pollinators appropriated size and correct work of blossoms ensure the reproductive success of this species.