Wild Bee Conservation in Pollinator-Independent Crop Systems

Abstract

Wild bees are undergoing global declines due to multiple interacting stressors including habitat loss, pesticides, climate change, and interactions with managed and non-native species. These threats are especially prevalent in agricultural landscapes, where natural habitats are replaced with intensively managed monocultures and bees are exposed to agrochemicals and managed pollinators. Pollinator-independent crops - those not reliant on animal pollination for yield or quality - may still support wild bee communities. Chapter 1 presents a systematic review of wild bee conservation research in pollinator-independent crop systems. The review shows strong geographic and crop biases, with commonly studied factors influencing wild bees including ground vegetation management, pesticide use, and surrounding landscapes. Chapter 2 explores how management practices influence wild bee communities in one such pollinator-independent crop, the wine grape (Vitis vinifera). Bee surveys across commercial vineyards showed that reduced between-row mowing consistently supported higher bee abundance and diversity. In contrast, practices like uniform cover cropping, organic production, and certified sustainable management had limited or sometimes negative impacts, suggesting the need for more targeted approaches and further research. Chapter 3 further examines how vineyard bee communities are impacted by local- and landscape-scale variables. Surrounding land-uses and soil factors within a 300m radius around vineyards were analyzed to determine their influence on bee abundance, diversity, and functional traits. Results reveal that wild bees were positively associated with a higher proportion of surrounding semi-natural habitats while sites with coarser soils supported more ground-nesting bees, highlighting the importance of considering both nesting and foraging resources for wild bee conservation and research in agroecosystems. Chapter 4 investigates whether wild bees use floral resources provided by pollinator independent crops by documenting foraging activity on wine grape flowers. Very few bees were observed using grapevine pollen, though some species from Apidae, Andrenidae and Halictidae were recorded. This suggests that wine grapes alone provide minimal floral resources for bees, emphasizing the importance of non-crop vegetation for sustaining bee populations in vineyard landscapes. Together, this thesis provides new insights into bee conservation within pollinator-independent crop systems and highlights practical strategies and research gaps for enhancing wild bee communities in agroecosystems.