Differential effects of farming practice on cuckoo bumblebee communities in relation to their hosts

Abstract

29 30 1. Bees are important for vital pollination of wild and crop plants, but are in 31 decline worldwide. Intensification of agriculture is a major driver of bee 32 decline. Organic farming practices are designed to limit environmental 33 impacts of agriculture and can increase bee abundance and species diversity. 34 However, studies have been heavily focused towards some guilds of bees, 35 overlooking others. This includes social brood parasites, cuckoo bumblebees, 36 an understudied bee lineage. Little is known about bumblebee host and 37 cuckoo population dynamics, and the effects of farming practice on cuckoo 38 bumblebees have never previously been evaluated. 39 2. To compare the effects of farming practice (organic vs conventional) on the 40 abundance, species diversity, and community dissimilarity of cuckoo 41 bumblebees and their hosts, we compared host and cuckoo community 42 metrics across ten matched pairs of organic and conventional farms in 43Yorkshire, UK. 44 3. As found by many previous studies, host bumblebees were more abundant 45 on organic farms than on conventional farms. Despite this, cuckoo 46 bumblebees were equally abundant on both farm types. Contrary to 47 prediction, community dissimilarity and species diversity were unaffected by 48 farm type for both host and cuckoo communities. 49 4. Synthesis and applications: Results suggest that cuckoo bumblebee 50 community metrics are not solely driven by host community metrics, and that 51 cuckoos may respond differently from their hosts to differences among 52 farming practices. This could, in turn, indicate that a unified management 53 practice is not sufficient to conserve all bumblebee species. 54 55 56