Preliminary study of wild bee communities (Anthophila) in Montpellier city parks

Several threats weigh on biodiversity, particularly pollinators such as wild bees. Land artificialization and urbanization, intensive agriculture and climate change are among these threats. Although urbanization can be a threat for pollinators, in urban contexts, parks and green spaces can serve as refuges for pollinators. This preliminary study aims to select a method for the long-term monitoring of bee communities in Montpellier's city parks and to gain an initial insight into the diversity and structure of these communities. Two protocols, fixed transects and a set of five indices of point abundance (IPA), were compared in six parks by three observers between March and June. More than 10,000 individuals belonging to 227 species were recorded. The structure of the communities remained relatively unchanged throughout the season and between parks, although the composition of the communities varied greatly. Statistical analyses (PERMANOVA) revealed that the communities are mainly influenced by location (the park) and sampling date (the passage). The effects related to the observer and the time of day are less significant but still noteworthy. Some more wooded parks, such as Lironde Park and Domaine Grammont, seem to attract less bee diversity. Others, such as Malbosc Park and the Jardin des Plantes, seem to attract greater bee diversity thanks to their heterogeneous habitats and management methods. Although the two protocols did not produce identical results, the resulting community structure is relatively comparable. Abundance per unit of time is similar between the two protocols, although IPAs detected slightly more species per unit of time. The fixed transect protocol showed less observer bias and is easier and faster to implement for the same sampling effort. We therefore recommend the fixed transect method for future monitoring due to its reproducibility, efficiency and reduced observer bias. A single IPA may be added to detect any specialist species located outside the transect line within a park.