Much more than bees-Wildflower plantings support highly diverse flower-visitor communities from complex to structurally simple agricultural landscapes

摘要

One goal of wildflower plantings is to promote biodiversity in intensively managed agricultural landscapes. Flower visitors of wildflower plantings encompass many ecologically and economically important species. However, most studies on flower visitors of wildflower plantings have focused on single or few prominent taxa (e.g., wild bees and hoverflies). In contrast, it remains largely unresolved how non-prominent flower visitors of the community are affected by wildflower resources, landscape context and time of the flowering season. We studied highly diverse flower-visitor communities on 14 wildflower plantings varying in flower abundance and richness and their surrounding landscape context within a 500 m radius (percentage arable land, presence of additional wildflower plantings). Flower visitors were sampled in the early (May-June) and late (June-July) flowering season and grouped as follows: managed honeybees, wild bees, hoverflies, all other flower visitors. Strikingly, only 81 (25.1%) of all 322 visiting species (50.0% of individuals) were bees or hoverflies, and 241 non-prominent 'other' visitor taxa were sampled, encompassing many ecologically and economically important species, e.g., parasitic wasps and non-syrphid Diptera. With the exception of honeybee abundance that was positively related to flower abundance, flower abundance and richness of wildflower plantings affected neither abundance nor richness of any visitor group. While a high amount of surrounding arable land decreased species richness of wild bees, richness of all other groups was unaffected. In contrast to the relatively weak abundance and richness responses at the group-level, we found strong species-specific responses to landscape context, resulting in substantial spatial and temporal turnover in community composition. In the early flowering season, wildflower plantings that were accompanied by additional local plantings and embedded within complex landscapes supported the highest abundances of habitat specialists (e.g. Bombus spp.), whereas isolated plantings were predominantly visited by agricultural generalists (e.g. predatory hoverflies and pollen beetles). These compositional differences diminished towards the end of the flowering season. Our study highlights the great conservation potential of wildflower plantings in agricultural landscapes. With the exception of wild bees, wildflower plantings support a high diversity of functionallycomplementary flower-visitor species from complex to structurally simple agricultural landscapes. These so-far overlooked flower visitors may have the potential to provide complementary ecosystem services and to step-in in agricultural settings where prominent providers have been lost. Assessments of the value of wildflower plantings to biodiversity conservation and agriculture require a shift away from solely focusing on prominent taxa and towards a more holistic appreciation of the entire flower-visitor community. (C) 2016 Elsevier B.V. All rights reserved.