Data from: Flower resource and land management drives hoverfly communities and bee abundance in semi-natural and agricultural grasslands

1. Pollination is a key ecosystem service, and appropriate management, particularly in agricultural systems, is essential to maintain a diversity of pollinator guilds. However, management recommendations frequently focus on maintaining plant communities, with the assumption that associated invertebrate populations will be sustained. 2. We tested whether plant community, flower resources and soil moisture would influence hoverfly (Syrphidae) abundance and species richness in floristically-rich semi-natural and floristically-impoverished agricultural grassland communities in Wales (U.K.), and compared these to two Hymenoptera genera, Bombus and Lasioglossum. Interactions between environmental variables were tested using generalised linear modelling, and hoverfly community composition examined using canonical correspondence analysis. 3. There was no difference in hoverfly abundance, species richness, or bee abundance, between grassland types. There was a positive association between hoverfly abundance, species richness and flower abundance in unimproved grasslands. However, this was not evident in agriculturally improved grassland, possibly reflecting intrinsically low flower resource in these habitats, or the presence of plant species with low or relatively inaccessible nectar resources. There was no association between soil moisture content and hoverfly abundance or species richness. 4. Hoverfly community composition was influenced by agricultural improvement and the amount of flower resource. Hoverfly species with semi-aquatic larvae were associated with both semi-natural and agricultural wet grasslands, possibly because of localised larval habitat. Despite the absence of differences in hoverfly abundance and species-richness, distinct hoverfly communities are associated with marshy grasslands, agriculturally improved marshy grasslands and unimproved dry grasslands, but not with improved dry grasslands. 5. Grassland plant community cannot be used as a proxy for pollinator community. Management of grasslands should aim to maximise the pollinator feeding resource, as well as maintain plant communities. Retaining waterlogged ground may enhance the number of hoverflies with semi-aquatic larvae.

1. 传粉是一项关键生态系统服务，而合理的管理（尤其在农业系统中）对维持多样的传粉者类群至关重要。然而当前的管理建议往往聚焦于植物群落的维护，默认伴随的无脊椎动物种群也将因此得以存续。
2. 本研究针对英国威尔士境内植物种类丰富的半自然草地与植物种类匮乏的农业草地生境，检验了植物群落、花资源与土壤含水量是否会影响食蚜蝇（Syrphidae）的种群数量与物种丰富度，并将其与膜翅目（Hymenoptera）下的熊蜂属（Bombus）和隧蜂属（Lasioglossum）进行对比。研究通过广义线性模型（generalised linear modelling）检验环境变量间的交互作用，并通过典范对应分析（canonical correspondence analysis）解析食蚜蝇的群落组成。
3. 两类草地生境中的食蚜蝇种群数量、物种丰富度以及蜂类种群数量均无显著差异。在未改良草地中，食蚜蝇的种群数量与物种丰富度与花资源丰度呈正相关关系，但该现象并未出现在农业改良草地中，这可能源于此类生境中花资源本底较低，或是存在花蜜量少或难以获取的植物类群。土壤含水量与食蚜蝇的种群数量及物种丰富度均无关联。
4. 食蚜蝇的群落组成受农业改良措施与花资源丰度的影响。幼虫为半水生的食蚜蝇物种与半自然及农业湿地草地均存在关联，这可能与其局地幼虫生境相关。尽管食蚜蝇的种群数量与物种丰富度并无组间差异，但沼泽草地、农业改良沼泽草地与未改良干旱草地分别对应特征鲜明的食蚜蝇群落，而农业改良干旱草地则未形成独特的食蚜蝇群落。
5. 草地植物群落无法作为传粉者群落的替代指标。草地管理应在维持植物群落的同时，最大化传粉者的觅食资源。保留积水地块或许能够提升具有半水生幼虫的食蚜蝇种群数量。