Mass flowering oilseed rape improves early colony growth but not sexual reproduction of bumblebees

By C. Westphal, I. Steffan‐Dewenter, T. Tscharntke. 2009

257 citations recorded by the source corpus.

Summary 1. Pollination is a vital ecosystem service, which is endangered by the ongoing declines of pollinators. These declines also affect bumblebees ( Bombus spp.), which are important generalist pollinators in agricultural landscapes. Most studies focussing on the conservation of bumblebees have investigated the effects of local flower-rich habitats on bumblebee density and diversity. However, bumblebee densities do not necessarily correlate with the colonies’ reproductive success (i.e. the presence or absence of males and/or queens). 2. We analysed the effects of landscape-wide availability of mass flowering oilseed rape Brassica napus on the growth and sexual reproduction of Bombus terrestris colonies. Thirty-two young colonies were established and monitored in different resource environments represented by 16 landscapes (circular study areas with 3000 m radius) with large or small amounts of oilseed rape. As an indicator of colony growth, we used weight gain, which was strongly correlated with the numbers of brood cells in the colonies. 3. The colonies gained significantly more weight in study areas with large amounts of oilseed rape particularly during early colony stages. 4. Despite early weight gain, the colonies in study areas with large amounts of oilseed rape did not reproduce more successfully. The frequencies of colonies that produced males and/or queens did not differ between the two resource environments. 5. Synthesis and applications . Early mass flowering oilseed rape has a beneficial effect on colony growth, which however, does not translate into a greater likelihood of colonies producing sexual offspring. This may be due to food plant scarcity later in the colony cycle. Conservation measures should enhance food plant availability in agricultural landscapes, particularly during the most critical phases of the colony cycle: the colony establishment in spring and the reproductive phase in mid- to late summer.

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

View Paper: https://www.semanticscholar.org/paper/389f3e89f2e0b9b82c58b2973a17f74b50c4e7d6

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Citations in the corpus

Massively Introduced Managed Species and Their Consequences for Plant–Pollinator Interactions (2017, background): “…resources for pollinators are mainly provided by wild flowering plants in seminatural remnants (e.g. grasslands, field margins, hedgerows; Ricketts et al., 2008; Rollin et al., 2013; Steffan-Dewenter and Tscharntke, 2001) and MFC for a short duration (Herrmann et al., 2007; Westphal et al., 2009).”
Bee declines driven by combined stress from parasites, pesticides, and lack of flowers (2015, background): “Some studies have found positive effects of proximity to canola on bumblebee colony growth and abundance (91, 92) and on numbers of nesting red mason bees Osmia bicornis (93, 94); others”
Frontiers inEcology and the Environment From research to action : enhancing crop yield through wild pollinators (2014, background): “Similarly, in Germany, canola improved bumble bee early-colony growth but not whole-season sexual reproduction (Westphal et al. 2009), and greater land cover of mass-flowering crops increased the number of bum- LA Garibaldi et al. Enhancing pollination services ble bee workers but not colony…”
Late-season mass-flowering red clover increases bumble bee queen and male densities (2014, unknown): “The lack of influence on reproductive success has been suggested to be caused by a deficiency of forage resources in late season (Westphal et al., 2009; Williams et al., 2012), but this hypothesis has not been tested.”
Spillover of functionally important organisms between managed and natural habitats (2012, background): “Recent studies found that mass-flowering of rape increases the growth of bumble bee colonies (Westphal et al., 2009).”
Mass‐flowering crops increase richness of cavity‐nesting bees and wasps in modern agro‐ecosystems (2014, background): “This numerical increase in worker bees, however, fails to translate into improved sexual reproduction later in the year when food resources are usually scarce in modern agro-ecosystems (Westphal et al., 2003, 2009).”
From research to action: Enhancing crop yield through wild pollinators (2014, background): “Similarly, in Germany, canola improved bumble bee early-colony growth but not whole-season sexual reproduction (Westphal et al. 2009), and greater land cover of mass-flowering crops increased the number of bumFigure 3.”