Land uses that support wild bee (Hymenoptera: Apoidea: Anthophila) communities within an agricultural matrix

Abstract

My main aim in this thesis was to explore if there are habitat elements within the agricultural matrix that support bee diversity and abundance. I examined the influence of land-use on bee diversity in a predominantly agricultural landscape at sites varying in habitat thought to be bee-friendly, such as semi-natural lands, grasslands, and crops providing bee forage. I sought to determine whether and to what extent these potentially bee-friendly land uses support diverse bee communities. Bees found near crops not providing forage, including corn, soybean, and wheat, had less functional diversity. Bees found near semi-natural lands that contained flowers providing bee forage had increased functional diversity. Wooded areas were associated with increased bee species richness and bee abundance, and wetlands were associated with greater bee abundance. Crops providing bee forage were associated with increased bee species richness and diversity. Altering land management practices to promote retention and enhancement of these land uses will help support diverse wild bee communities within agricultural matrices. I also compared responses of wild bees and commercially managed honey bee colonies to bee-friendly land uses. Both honey bees and wild bees responded positively to semi-natural lands and crops providing bee forage. Examination of past and present bee and floral visitation records revealed a 16 to 30% loss of species richness. The bee genera Lasioglossum, Mellisodes, Halictus, and Ceratina increased in relative abundance more than 50%, while the genera Bombus, Megachile, and Colletes, decreased in relative abundance more than 65% and the genus Andrena decreased in relative abundance by 47%. The plant genera that received the most bee visits from 2010 to 2012 were Melilotus, Sonchus, and Cirsium, while the plants with the highest number of bee species visitors were Solidago, Cirsium, and Sonchus. The plant genera Zizia, Hydrophyllum, and Dalea all received more visitation in the past. This survey of flower visitors revealed a community in need of conservation with a remaining species pool to enable recovery given improvements in available habitat.