Flower-visiting and pollen-carrying arthropods of Leucojum aestivum L. (Amaryllidaceae) in wild, reintroduced and ex situ populations

Leucojum aestivum L. is a wetland-dependent perennial geophyte occurring in Europe and western Asia. It is self-incompatible, with high level of fruit-set and seed-set. Yet, its pollinators are poorly known. Here, we present the most recent research on potential pollinators of L. aestivum. We collected data on flower-visiting and pollen-carrying arthropods in three populations of the species in the River Po plain (N-Italy), where L. aestivum occurs mainly in forests with Alnus glutinosa and Fraxinus sp. pl. close to rivers. We studied a wild population, a new reintroduced population and an ex situ population located at the Botanical Garden of the University of Pavia. Our study identified 18 arthropod taxa carrying L. aestivum pollen; the soft-winged flower beetle Dasytes plumbeus (Coleoptera: Melyridae) and the sac-spider Clubiona sp. pl. (Araneae: Clubionidae) were the most frequent visitors. Hymenoptera only occasionally visited L. aestivum flowers (e.g. the sweat bee Lasioglossum punctatissimum). D. plumbeus, the long-horned beetle Grammoptera ruficornis (Coleoptera: Cerambycidae), Clubiona sp. pl. and L. punctatissimum resulted in the taxa with the highest average abundance of pollen grains on their body suggesting a potential role in L. aestivum pollination. Differences in flower-visiting and pollen-carrying arthropods were observed between the three populations, with a decreasing taxonomic diversity of visiting species from the wild population to the ex situ population. Our results, based on direct observation in the field, are partially in contrast with a previous study on L. aestivum pollinators that suggested diurnal and nocturnal Lepidoptera and occasionally bees as main pollinators for the species.