Evaluating wild bee diversity across key habitats of two Belgian National Parks

Protected areas are central to biodiversity conservation, but management efforts usually prioritise vertebrates or plant communities. The effectiveness of these initiatives in safeguarding insect diversity, particularly wild bees, remains poorly studied, and existing evidence shows contrasting results. To address this gap, we surveyed bee communities for five months in two recently established national parks in Belgium, namely the Semois Valley (SVNP) and Entre-Sambre-et-Meuse (ESEMNP), across a range of habitats. First, we evaluated whether mean alpha diversity (Hill numbers) and beta diversity varied across parks and habitats. Then we assessed whether threatened bee species (as categorized by the Belgian Red List) were associated with specific habitats or park. Collectively, these analyses enabled a comparative assessment of these two parks, highlighting their relative conservation value and identifying key habitats for wild bee conservation. We hypothesized that the mesic and calcareous grasslands would support the highest diversity in the national parks SVNP and ESEMNP respectively. Overall, we recorded 2278 bee specimens belonging to 153 species, including 30 threatened species, with the Semois Valley National Park harbouring higher overall mean alpha diversity than the Entre-Sambre-et-Meuse National Park. While no significant differences in alpha diversity were observed among habitats in the first National Park, calcareous grasslands and hay meadows in the second National Park supported the highest alpha diversity of wild bees, emphasizing the high conservation value of these habitats. Conversely, tall-herb habitats consistently showed the lowest alpha diversity across both national parks. Ensuring the persistence of these parks and their key habitats through targeted management and connectivity measures, will be essential for maintaining bee diversity in Belgium.