Exploring the bee fauna on the islands of Brittany (France): an initial survey reveals a remarkable species richness.

Islands are areas where biodiversity conservation is of the utmost importance and is particularly challenging due to the isolation and vulnerability of animal and plant populations. The coastline of Brittany includes a large number of islands, which vary greatly in size, distance from the mainland, landscape composition and climate. Until recently, virtually nothing was known about the bees on these islands, but a number of studies have been carried out in recent years, allowing an initial assessment to be made. The aim of this article is to provide an overview of the bee fauna of the islands of Brittany, in terms of species richness, species composition and rarity status. In total, we gathered records of 188 wild bee species on 25 continental islands, located on both the north and south coasts of Brittany. For most of the islands, we obtained only occasional data, but a few have benefitted from intensive surveys, with data collected throughout the entire flight period and over several years and in different locations and habitat types. For four islands, we considered that the current knowledge is relatively good: Groix (113 wild bee species), Houat (82 species), Hoedic (64 species) and Ouessant (57 species). In addition to the number of species, this study shows that the islands host many species that are rare at regional or national level. Our results highlight the importance of taking bees into account when managing habitats and defining protected areas in islands, in order to conserve both food resources and nesting sites for these pollinator insects.