Development of regionally optimized flower mixtures for supporting the wild bee pollinators in Serbia

Abstract

Intensive agricultural practices have led to landscape simplification, resulting in a significant reduction of essential floral resources for various pollinator groups. Among the mitigation measures, EU and national strategies promote the establishment of sown flower strips, tailored to attract and sustain pollinator populations in various local and regional contexts. Within the EcoStack project (H2020), we aimed to develop regionally specific flower mixtures suitable for supporting the wild bee populations in large agricultural areas of Serbia. In the study conducted during 2021–2022, we tested a total of 32 flower species (24–25 per year; randomised block design of four square metre plots per sown species), of which 26 were established successfully (variably between the years). We carried out multiple timed sampling of bees from May through July, and recorded 20 bee genera (15–19 per year). The three most attractive plants (based on the frequency of wild bee visitation) were: Cynara scolymus>Phacelia tanacetifolia>Coriandrum sativum in 2021, and Phacelia tanacetifolia>Coriandrum sativum>Daucus carota in 2022. Other prospective plants were: Pimpinella anisum, Centaurea cyanus, Sinapis alba, Onobrychis viciifolia and Calendula officinalis. Phacelia tanacetifolia attracted the highest number of visiting bee genera in both years (9–12). Four bee genera (Lasioglossum, Apis, Andrena, Hylaeus) contributed each with more than 10% of all visits in at least one year (totalling 73 77%). The analysis of bee-plant visitation network parameters yielded similar results in both years. The networks were relatively simple, with low connectance and low specialisation. Among the bee genera Andrena, Halictus and Seladonia showed the lowest specificity in both years, while Lasioglossum and Apis only in 2021, whereas among the plants Phacelia tanacetifolia had the lowest specificity in both years. Starting with these initial findings, we are now extending the analyses of further plant combinations and of interactions at bee species level.