Reproductive Biology of the Desertic Micro-Endemic Nolana chapiensis (Solanaceae: Nolanoideae) in Southern Peru: Self-Incompatibility and Solitary Bees as Exclusive Pollinators

Understanding the reproductive biology of microendemic species is crucial for developing effective conservation strategies since they frequently have small, restricted and threatened populations. Nolana chapiensis (Solanaceae: Nolanoideae) is a desert microendemic species found in southern Peru that was studied in the Arequipa department at an altitude of 2280 m, from March to April 2023–2024. This study documents floral features, breeding system, pollination process and fruiting success. The breeding system was assessed by isolating plants from pollinators (bagging). Pollination processes were observed in the field using photo and video documentation. Flowers exhibited a short lifespan (3–5 days) with opening and closing events correlated with fluctuations in temperature. Nolana chapiensis is pollinator-dependent and self-incompatible (unable to set fruit without cross-pollination mediated by pollinators). All five identified pollinator species are solitary bees, with Andrenidae species accounting for 83.91% of visits. Most pollinators are female bees that pollinate during pollen-collecting activities. However, Andrenidae males also contribute to pollination while waiting for females inside the floral tube. Natural fruiting success per individual was high, ranging from 35.15% to 74.77%. While high fruiting success might be unexpected in desert environments and in self-compatible species, in this case, it could be attributed to the diversity and behaviour of pollinator species. This study represents the first detailed study of reproductive biology within the genus, coupling breeding system experiments with detailed pollinator observations.