Reproductive biology of Santolina ligustica Arrigoni, a rare narrow-ranged species: implications for conservation

Santolina ligustica is a rare narrow-ranged species endemic to Liguria (Italy) for which a likely trend of decline has been recorded. For this reason, it would be important to assess the reproductive biology of this endemic species. In this study, we investigated the plant–pollinator interactions, the reproductive mode of the plant, and we evaluated both reproductive efficiency and seeds’ germination performances. Santolina ligustica is an obligate cross-pollinating species with a generalist pollination system. The most frequent insects are Coleoptera belonging to the genus Oedemera. Seed set is low, but the seeds germinate under a wide range of temperatures. Taken together, our results indicate that S. ligustica is an insect pollinated and self-incompatible plant, in which low visitation rate, secondary pollen presentation and/or lack of compatible mate may cause a low seed set per capitulum. Nevertheless, the high number of capitula per plant and the high percentage of germination may assure high number of seedlings. Thus, the survival of S. ligustica is probably threatened by other factors such as fragmented distribution and habitat reduction because of land-use change. Under this scenario, we proved that species’ decline is not directly related to reproductive failure and different studies are desirable to provide suggestions for the species conservation.