The importance of landscape and spatial structure for hymenopteran‐based food webs in an agro‐ecosystem

Abstract

Summary1. Understanding the environmental factors that structure biodiversity and food webs among communities is central to assess and mitigate the impact of landscape changes. 2. Wildflower strips are ecological compensation areas established in farmland to increase pollination services and biological control of crop pests and to conserve insect diversity. They are arranged in networks in order to favour high species richness and abundance of the fauna. 3. We describe results from experimental wildflower strips in a fragmented agricultural landscape, comparing the importance of landscape, of spatial arrangement and of vegetation on the diversity and abundance of trap-nesting bees, wasps and their enemies, and the structure of their food webs. 4. The proportion of forest cover close to the wildflower strips and the landscape heterogeneity stood out as the most influential landscape elements, resulting in a more complex trap-nest community with higher abundance and richness of hosts, and with more links between species in the food webs and a higher diversity of interactions. We disentangled the underlying mechanisms for variation in these quantitative food web metrics. 5. We conclude that in order to increase the diversity and abundance of pollinators and biological control agents and to favour a potentially stable community of cavity-nesting hymenoptera in wildflower strips, more investment is needed in the conservation and establishment of forest habitats within agro-ecosystems, as a reservoir of beneficial insect populations.

Flower preferences and pollen transport networks for cavity‐nesting solitary bees: Implications for the design of agri‐environment schemes

“…Nest boxes followed designs used successfully in previous studies (Fabian et al., 2013; Steckel et al., 2014; Tylianakis, Tscharntke, & Lewis, 2007; Williams & Kremen, 2007). Each consisted of a 20 cm long plastic cylinder, of diameter 10 cm, filled with hollow, untreated sections of bamboo with apertures ranging from 4 to 12 mm in diameter (Falk, 2015; Tylianakis et al., 2007).…”

Modeling Pollinator Community Response to Contrasting Bioenergy Scenarios

“…Wind-pollinated crops, annual flowering crops, forests, and grasslands were included as explanatory variables because they accounted for a large proportion of the land cover and (with the exception of forest) are the cover classes that will change under contrasting bioenergy scenarios. Although the proportion of forest does not change under the different bioenergy scenarios, this variable was retained in the model because forests are ecologically important to pollinators, providing nesting habitat and floral resources early in the season [37], [38], [39].…”

Weed-insect pollinator networks as bio-indicators of ecological sustainability in agriculture. A review

“…They provide suitable ecological niches for many pollinators. The introduction of wildflower strips favors a potentially stable community of cavity-nesting hymenoptera (Fabian et al 2013), with particular reference to honey bees (Decourtye et al 2010(Decourtye et al , 2011. But the efficiency of flowering areas managed for bees can be influenced by the presence of alternative flowers in the seminatural habitats close by (Henry et al 2012;Blaauw and Isaacs 2014).…”