Utilisation of pollen resources by bumblebees in an enhanced arable landscape

Carvell, Claire; Meek, Bill; Broughton, Richard; Sparks, Tim; Pywell, Richard; Westrich, Paul; Nowakowski, Marek. 2004 Utilisation of pollen resources by bumblebees in an enhanced arable landscape. NERC/Centre for Ecology & Hydrology, 32pp. (CEH Project number: C02362) (Unpublished)

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Pollen is an essential resource for bumblebees, yet this is often overlooked in studies of their foraging requirements. The decline of bumblebees across the UK and rest of Europe has prompted conservation measures to consider the provision of pollen as well as nectar resources, particularly in intensive agricultural landscapes where the pollination service bumblebees provide is so important. This report details a study carried out in July 2003 to investigate the utilisation of pollen from different forage plant species by two bumblebee species with contrasting ecologies (Bombus pascuorum and Bombus terrestris/lucorum) across an enhanced arable landscape. An area of 1.96 km2 was divided into grid squares of 100m x 100m. Pollen loads were sampled from foraging bumblebees in eight random squares within the centre of this grid, and every square was surveyed in detail to map the distribution and abundance of all plant species in flower. Each pollen load was analysed to identify the pollen genera and/or species present, and to estimate the percentage species composition of the load. The two bumblebee species showed specialization towards pollen from contrasting species. B. pascuorum visited flowers of 23 different species to collect pollen, and although 76% of pollen loads were mixed, many were dominated by species from the Fabaceae, especially Trifolium pratense. B. terrestris/lucorum loads contained pollen from 17 species, only 32% of these were mixed, and Borago officinalis was the dominant pollen type. The majority of pollen loads of both bee species were dominated by species which had been sown in mixtures under the Countryside Stewardship Scheme. Although several unsown species were visited for pollen, they were only present in a few loads and at low proportions. The composition of a bumblebees’ pollen load did not always relate to the forage plant species on which that bee had been caught. Calculation of a pollination probability index (PPI) showed that bumblebees tended to collect large amounts of conspecific pollen from their preferred pollen forage plants (ie. Trifolium pratense, Borago officinalis). This suggested that in our study area, bumblebees may be more efficient pollinators of certain forage plant species than others. Maps of flower abundance and distribution showed that the study landscape contained many diverse patches of flowering plants, particularly of the Fabaceae, which are encouraged under agri-environment schemes such as Countryside Stewardship. The area was therefore of higher quality in terms of pollen resources for B. pascuorum than B. terrestris/lucorum. B. pascuorum was the more abundant species, probably able to undertake relatively short foraging flights with guaranteed rewards, thus enhancing colony success. ·In conclusion, restoration measures, such as those within the agri-environment schemes, must consider the pollen requirements of all bumblebee species in order to conserve populations and retain their important pollination service in agricultural landscapes.

Item Type: Publication - Report
Programmes: CEH Programmes pre-2009 publications > Biodiversity
UKCEH and CEH Sections/Science Areas: _ Ecological Processes & Modelling
Funders/Sponsors: English Nature
Additional Keywords: Bombus pascuorum, Bombus terrestris/lucorum
NORA Subject Terms: Agriculture and Soil Science
Ecology and Environment
Related URLs:
Date made live: 04 Jun 2009 14:05 +0 (UTC)

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