Défense de thèse de doctorat en sciences géographiques

Wild bee diversity across space and time : the role of land use/land cover and climate

Jury

Nicolas TITEUX (German Centre for Integrative Biodiversity Research), Luisa G. CARVALHEIRO (Universidade Federal de Goias), Jacobus C. BIESMEIJER (Leiden University), co-promoteur, Nicolas VEREECKEN (ULB), Jesus AGUIRRE-GUTIERREZ (University of Oxford), Catherine LINARD (UNamur), présidente, Nicolas DENDONCKER (UNamur), promoteur

Résumé

Wild bees have experienced significant changes in many areas over the last 100 years, showing large shifts in their distribution patterns, declines in diversity and abundance, and local extinctions. To interpret historical dynamics, recognize present day patterns, model potential futures, and mitigate the influence of rapid global changes, it is essential to understand in detail the different drivers of these changes. Land use/land cover (LULC) and climate change have been outlined as two of the most important factors for wild bees. Consequently, the general objective of this thesis is to examine how LULC and climate conditions impact the diversity and distribution of wild bees at different spatial and temporal scales.

The research aims to; (1) test the efficacy of historical collections records with statistical modeling tools, specifically species distribution models (SDM), to understand wild bee distributions in the present and future, (2) to provide a novel understanding of how wild bee community assemblages are structured and what drives this structure; and also (3) to quantify and compare how past, present, and future changes to bumblebee distributions are influenced by LULC and climate changes.

The results highlight the significance of historical wild bee occurrence data and the utility of SDMs for investigating key environmental requirements of wild bee species and assessing long-term trends. We show that wild bee distribution patterns are highly dependent on LULC conditions, and that LULC change must be considered alongside climate change in future scenarios for wild bees. It also indicates the importance of incorporating ecological factors, such as traits and phylogenetic relationships into these approaches to improve the knowledge of the processes behind these patterns.Finally, this thesis provides advice to conserve wild bees at the individual species level but also for species assemblages, and at the landscape scale. As wild bee species are expected to continue to decline globally this thesis increases the knowledge and tools available to ensure that high diversity wild bee communities continue to persist.

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