Reproductive biology and pollinators of Musschia wollastonii Lowe (Campanulaceae)

Abstract

Understanding the reproductive biology of plants is particularly relevant for the conservation of rare, threatened or endemic plants. Musschia wollastonii Lowe is a rare, monocarpic, neoendemic species of the island of Madeira with a complex reproductive biology including outcrossing and selfing. However, nothing is known about the extent of the dependence of the species on pollinators for its reproduction, a possible incompatibility system, or the extent of selfing. We found that M. wollastonii is self-compatible and shows spontaneous but delayed selfing. Outcrossing is promoted by protandry, weak dichogamy, and a mechanism of secondary pollen presentation on the abaxial surface of the stigmatic lobes. The four-month flowering period and large inflorescence, traits that promote cross-pollination, suggest a mixed mating system. Observed flower visitors were insects from the Syrphidae and Drosophilae (both Diptera), Nymphalidae (Lepidoptera) and Vespidae (Hymenoptera) families. All insect flower visitors observed were pollen thieves and had thus potentially a negative impact on reproductive success, but a positive role as pollinators is suggested for syrphids and the butterfly Pararge xiphia (Nymphalidae). Although reported by other authors, no bird visitations were recorded in the studied habitat.