Mass-flowering crops enhance wild bee abundance

Andrea Holzschuh,Ingolf Steffan-Dewenter,Teja Tscharntke,Carsten F Dormann

doi:10.1007/s00442-012-2515-5

Andrea Holzschuh, Ingolf Steffan-Dewenter + Show 2 more

Open Access

https://doi.org/10.1007/s00442-012-2515-5

Copy DOI

Abstract

Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 % when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 % higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-012-2515-5) contains supplementary material, which is available to authorized users.

Highlights

Communicated by Riccardo Bommarco.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.A
We recorded 2,473 brood cells in nests of Osmia bicornis, 1,104 brood cells in 12 grasslands adjacent to oilseed rape, brood cells in 14 grasslands isolated from oilseed rape, 606 brood cells in 10 oilseed rape fields adjacent to grasslands, and 48 brood cells in 2 oilseed rape fields isolated from grassland
The presence of adjacent grassland had a positive effect on the number of brood cells in oilseed rape resulting in 606 brood cells in nests of the O. bicornis in 10 of 17 oilseed rape fields adjacent to grassland (59 % of the fields), but only 48 brood cells in 2 of 17 oilseed rape fields isolated from grassland (12 % of the fields; GLM with quasibinomial errors: F1,32 = 8.3, P = 0.007; Fig. 1a)

Summary

Methods

Study sitesThe study was carried out in 2007 near the city of Gottingen (51.5°N, 9.9°E), Lower Saxony, Germany. Each of the 17 study grasslands of category 2 was in 1–15 m distance of one of the studied oilseed rape fields of category 3. All study sites where we recorded Osmia bicornis in our traps were included in the analyses of pollen contents and brood cell numbers (in all cases [9 brood cells per site): (1) 14 grasslands isolated from oilseed rape; (2) 12 grasslands adjacent to oilseed rape; and (3) 10 oilseed rape fields adjacent to grasslands. Category 4 (oilseed rape fields isolated from grasslands) was excluded from the analyses of pollen contents and brood cell numbers because only 2 sites had been colonized by O. bicornis. The 34 oilseed rape fields of category 3 and 4 were included in an analysis of O. bicornis incidence (see below)

Results

Discussion

Conclusion