Assessing the attractiveness of native wildflower species to bees (Hymenoptera: Anthophila) in the southeastern United States

Pesticide use, disease, climate change, and habitat loss associated with agricultural intensification and urbanization have contributed to the decline of numerous insect groups. Recent government incentives have recognized the importance of supplementary wildflower plantings to support native bee populations, yet little information exists on the attractiveness of recommended plant species to bees. We evaluated the bee attractiveness of 18 native wildflower species belonging to 6 families (Apiaceae, Apocynaceae, Asteraceae, Fabaceae, Lamiaceae, and Verbenaceae) commonly recommended by the U.S. Department of Agriculture – Natural Resource Conservation Service (USDA-NRCS) to land managers in the southeastern United States. To accomplish this, we planted the 18 wildflower species in separate 1 m2 plots arranged in a randomized block design with four replicates in Auburn, Alabama, USA. We conducted floral counts and timed sweep netting events to assess each species’ attractiveness to bees from May-November 2019. We also evaluated the floral preferences of seven bee taxa (<em>Apis mellifera</em>, <em>Halictus poeyi/ligatus</em>, <em>Bombus griseocollis, Bombus impatiens, Lasioglossum </em>spp., <em>Megachile </em>spp., and <em>Xylocopa virginica</em>) to the planted wildflower species. We found that <em>Asclepias tuberosa, Gaillardia pulchella, </em>and <em>Verbena hastata </em>attracted the greatest abundance, richness, and diversity of native bees compared to the other wildflower species. While several wildflower species attracted low abundance, richness, and diversity of native bees, they are still ecologically important for attracting uncommon or specialist bee species. Each bee taxa were attracted to a particular combination of planted wildflower species; collectively, <em>Asclepias tuberosa, Gaillardia pulchella, </em>and <em>Verbena hastata </em>attracted 89% of all be taxa in the study, which exemplifies the importance of including them in a wildflower mixture to attract native bees. Our results highlight that each species of native wildflower varies in the abundance, richness, and diversity of native bees they attract; this could be considered in the decision-making of landowners and land managers to promote wildflower plantings to reflect their needs.

农药施用、病害、气候变化以及农业集约化与城市化引发的栖息地丧失，共同导致了众多昆虫类群的种群衰退。近年来，相关政府激励政策已认可补充种植野花对维持本土蜂群的重要性，但目前关于推荐植物物种对蜜蜂的吸引效果的相关研究信息仍较为匮乏。本研究评估了美国东南部地区土地管理者常用的、由美国农业部自然资源保护局（USDA-NRCS）推荐的18种本土野花物种对蜜蜂的吸引效果，这些野花分属6个科：伞形科（Apiaceae）、夹竹桃科（Apocynaceae）、菊科（Asteraceae）、豆科（Fabaceae）、唇形科（Lamiaceae）以及马鞭草科（Verbenaceae）。为开展该评估，我们在美国阿拉巴马州奥本市将18种野花分别种植于独立的1平方米样地中，采用随机区组设计并设置4次重复。2019年5月至11月期间，我们通过花量调查与定时扫网采样的方式，评估各野花物种对蜜蜂的吸引效果。此外，我们还评估了7个蜂类类群对所种植野花物种的花部偏好，这7个蜂类类群分别为：西方蜜蜂（*Apis mellifera*）、波伊隧蜂/侧条隧蜂（*Halictus poeyi/ligatus*）、灰胸丸熊蜂（*Bombus griseocollis*）、印巴熊蜂（*Bombus impatiens*）、隧蜂属（*Lasioglossum* spp.）、切叶蜂属（*Megachile* spp.）以及木蜂（*Xylocopa virginica*）。研究结果显示，与其余野花物种相比，块根马利筋（*Asclepias tuberosa*）、美丽天人菊（*Gaillardia pulchella*）以及狭叶马鞭草（*Verbena hastata*）所吸引的本土蜜蜂个体数量、物种丰富度及多样性均为最高。尽管部分野花物种所吸引的本土蜜蜂个体数量、物种丰富度及多样性均较低，但它们对于吸引稀有或特化蜂类仍具有重要的生态价值。不同蜂类类群均偏好特定的野花物种组合；总体而言，块根马利筋、美丽天人菊与狭叶马鞭草共吸引了本研究中89%的蜂类类群，这体现了将这三种野花纳入混合种植群落以吸引本土蜜蜂的重要性。本研究结果表明，不同本土野花物种所吸引的本土蜜蜂个体数量、物种丰富度及多样性均存在差异；土地所有者与管理者在制定推广野花种植的决策时，可参考该研究结果以匹配自身需求。