Titre de la dissertation/ From Species Delimitation to Conservation: Integrative Approaches for Lasioglossum (Hymenoptera: Halictidae) and Italian Wild Bees

 Promoteur: Monsieur Denis Michez

Résumé de la dissertation: Wild bees are pollinators of crucial importance to maintain ecosystem services, biodiversity, and food production. However, their taxonomy and conservation status are still poorly understood, especially in Mediterranean regions such as Italy. The present thesis develops integrative taxonomy methods, studies historical collections, and develops ecological analysis to better understand Italian wild bees, with a focus on the species-rich genus Lasioglossum Curtis, 1833.In Chapter 1 of the thesis, several taxonomic ambiguities are resolved thanks to the combined analysis of morphological and genetic data. Two Mediterranean taxa, Lasioglossum angustifrons (Vachal, 1892) and L. fertoni (Vachal, 1894), are confirmed as distinct species, while a new Sardinian-Corsican endemic, L. inexpectatum Flaminio & Pauly, 2024, is described. Following these findings, the Italian Lasioglossum fauna is thoroughly revised in Chapter 2. We did consider historical collections in Italian and European fauna, recently collected specimens from different national and personal sampling. An original identification key is provided that allows an accurate species-level determination of Lasioglossum throughout Italy and neighbouring regions. In chapter 3, long-term population trends are determined by integrating digitized collection data from major Italian collections (e.g. Roma, Firenze, Genova, Torino) with recent monitoring records, showing species-specific patterns of expansion and decline that are linked to ecological traits, sociality, and nesting behaviour. The analyses reveal positive trends for several Bombus species and many of their social parasites, but marked declines in ground-nesting bees and larger cavity-nesting species, highlighting differences in trends across ecological groups and a mismatch with some assessments in the European Red List of Wild Bees. In Chapter 4, we explore one potential driver of the decline of Italian fauna: parasite spillover. A survey of the prevalence of honey bee pathogens (viruses, microsporidian parasites, fungal pathogens and trypanosomatid gut parasites) in wild species shows widespread exposure, and that ecological and landscape factors affect infection risk. Ground-nesting, oligolectic, and parasitic species are confirmed as particularly vulnerable, indicating that pathogens may be a contributory factor to declines, alongside habitat loss, climate change, and agricultural intensification.Through the combination of taxonomy, population ecology, and epidemiology, taxonomic puzzles within Italian wild bees are highlighted, integrative approaches are demonstrated as being efficient for delineating conservation units, and tools are provided for evidence-based biodiversity management. The results emphasize that proper species delimitation forms a basis for linking ecological information to conservation strategies for protecting wild bees in Italy and across the Mediterranean.