Bees and crops in Spain: an update for melon, watermelon and almond

Abstract

Summary Pollinators of most of the plants cultivated in the Mediterranean regions of Europe are still unknown. We provide new data and we review previously available information on bees (Apoidea) associated with three economically important crops in Spain: melon (Cucumis melo L.), watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) and almond (Prunus dulcis (Mill.) D.A.Webb). We found that, overall, 98 bee species spanning four families visit flowers of the studied crop species, and 46 additional species were sampled within the crops with pan-traps. The bee assemblages visiting melon include 7–33 species, with moderate to high importance of small Lasioglossum (Halictidae) and of honey bee (Apis mellifera Linnaeus, 1758: Apidae), and in one case of small Ceratina: Apidae. Watermelon flowers are visited by 11–14 species of bees, with highest abundance of honey bees or of small Lasioglossum, depending on the locality. Bees collected on almond trees included 12–37 species, with the honey bee and medium-size to large Andrena (Andrenidae) and Osmia (Megachilidae) being predominant. The new samples expanded the geographical distributions of nearly one-fourth of the collected species. Diversity estimators slightly varied even within fields of the same crop, and a cluster analysis suggested both a certain overlap between melon and watermelon and a role of geographical distance on similarity among bee assemblages, though these patterns were much clearer using presence data rather than abundances. Below-ground-nesting and solitary species were more frequently collected than above-ground-nesting and eusocial species, but for melon and watermelon the highest abundances were recorded for eusocial species. Almost exclusively polylectic species visited the flowers of the three studied crops. The results of this study could help in planning conservation actions to maintain this important diversity of potential pollinators in Spanish areas covered by these crops.