Providing foraging resources for solitary bees on farmland: current schemes for pollinators benefit a limited suite of species

By T. Wood, John M. Holland, Dave Goulson. 2017

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1. Changes in agricultural practice across Europe and North America have been associated with range contractions and a decline in the abundance of wild bees. Concerns at these declines has led to the development of flower-rich agri-environment schemes as a way to enhance bee diversity and abundance. Whilst the effect of these schemes on bumblebee species (Bombus spp.) has been well studied, their impact on the wider bee community is poorly understood. 2. We used direct observations of foraging bees and pollen load analysis to quantify the relative contribution that sown flowers (i.e. those included in agri-environment scheme seed mixes) make to the pollen diets of wild solitary bees on Higher Level Stewardship farms (HLS) implementing pollinator-focused schemes and on Entry Level Stewardship farms (ELS) without such schemes in southern England, UK. 3. HLS management significantly increased floral abundance, and as the abundance of sown flowers increased these sown plants were utilised for pollen by a greater proportion of the solitary bee species present. However, the overall proportion of pollen collected from sown plants was low for both direct observations (27.0%) and pollen load analysis (23.3%). 4. At most only 25 of the 72 observed species of solitary bee (34.7%) were recorded utilising sown plants to a meaningful degree. The majority of solitary bee species did not collect pollen from flower species sown for pollinators. 5. Total bee species richness was significantly associated with plant species richness, but there was no difference in the total species richness of either bee or flowering plant species between HLS and ELS farms. 6. Synthesis and applications. These results show that the majority of solitary bee species present on farmland in the south-east of England collect the majority of their pollen from plants that persist unaided in the wider environment, not from those included in agri-environment schemes focused on pollinators. If diverse bee communities are to be maintained on farmland, existing schemes should contain an increased number of flowering plant species and additional schemes that increase the diversity of flowering plants in complementary habitats should be studied and trialled.

Subfields: Ecology, Evolution, Behavior and Systematics, Genetics, Insect Science

View Paper: https://www.semanticscholar.org/paper/93ea73b814c7fdd95ddab8ce257a0311dce83e0a

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Citations in the corpus

Insect pollinators collect pollen from wind‐pollinated plants: implications for pollination ecology and sustainable agriculture (2018, background): “Recent evidence has shown that cultivated wildflower plantings are not visited by pollinators as often as wild plants, and may do little to support the persistence of local pollinator populations (e.g. Wood et al., 2017).”
Pollination reservoirs for wild bee habitat enhancement in cropping systems: a review (2017, background): “To date, most pollen load analyses have relied upon painstaking visual identification of each pollen grain (Carvell et al. 2006; Venturini 2015; Wood, Holland, and Goulson 2016).”
Foraging distances in six species of solitary bees with body lengths of 6 to 15 mm, inferred from individual tagging, suggest 150 m-rule-of-thumb for flower strip distances (2020, background): “…the relatively small spatial and temporal scale of their life cycles, habitat ranges, and nesting behaviour (Westrich 1996; Gathmann and Tscharntke 2002; Greenleaf et al. 2007; Franzén et al. 2009; Zurbuchen et al. 2010a; Wood et al. 2016), which makes them vulnerable to landscape fragmentation.”
The potential of different semi-natural habitats to sustain pollinators and natural enemies in European agricultural landscapes (2019, background): “Some of these species have been suggested as important floral resource species in other European agroecosystems for bees (Carvell et al., 2006; Requier et al., 2015; Wood et al., 2017).”