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Critical resource levels of pollen for the declining bee Andrena hattorfiana (Hymenoptera, Andrenidae)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
2007 (English)In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 134, no 3, 405-414 p.Article in journal (Refereed) Published
Abstract [en]

The native bee fauna provides an important ecosystem function, but a large proportion of this fauna in Europe is threatened as a result of habitat loss and fragmentation. The solitary bee Andrena hattorfiana is specialised on collecting pollen from the plant-family Dipsacaceae. In northern Europe the major pollen resource is the insect-pollinated herb Knautia arvensis. We quantified the available K. arvensis resource, measured habitat characteristics and performed a flower-visitor survey in 57 well-defined K. arvensis populations in southern Sweden. There was a strong relationship between bee and plant population sizes. In populations with A. hattorfiana present (N=26), the female bees utilised on average 39% (12-80%) of the total available pollen resource. The nest architecture and nesting biology of A. hattorfiana is described for the first time. By excavating nests, we found that the provisioning for one average bee nest (containing 6 cells) required ca. 72 inflorescences or 11 plant individuals. The results suggest a certain minimum pollen amount needed to host an A. hattorfiana population. For example, for a population of ten reproducing A. hattorfiona female with the average degree of utilisation, the critical resource was predicted as 156 +/- 16 individuals (+/- SE) of the plant K. arvensis, which corresponds to 780 inflorescences or 36,731,978 pollen grains. These findings suggest that calculations via a 'pollen budget' can predict critical resources for a given size of specialised bee population, and thereby provide a tool in conservation.

Place, publisher, year, edition, pages
2007. Vol. 134, no 3, 405-414 p.
Keyword [en]
extinction; minimal resource; oligolecty; pollen limitation; specialisation; threshold
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-94776DOI: 10.1016/j.biocon.2006.08.030ISI: 000244385100012OAI: oai:DiVA.org:uu-94776DiVA: diva2:168752
Available from: 2006-09-21 Created: 2006-09-21 Last updated: 2011-02-15Bibliographically approved
In thesis
1. To Bee or Not to Be: Critical Floral Resources of Wild-Bees
Open this publication in new window or tab >>To Bee or Not to Be: Critical Floral Resources of Wild-Bees
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In recent decades, the development of strategies to prevent or slow the loss of biodiversity has become an important task for ecologists. In most terrestrial ecosystems wild-bees play a key role as pollinators of herbs, shrubs and trees. The scope of this thesis was to study 1) pollinator effectiveness of specialist bees vs. generalist flower-visitors, 2) critical floral resources for wild-bees, and 3) methods to estimate the size of wild-bee populations. The wild-bee species Andrena hattorfiana and A. marginata were used as model species. These two species are specialized on pollen from the plant family Dipsacaceae.

The bee A. hattorfiana was found to be a frequent visitor but a poor pollinator of its preferred food-plant Knautia arvensis. The female bees exert such a strong preference for pollen-producing inflorescences that they likely have deleterious effects on the plant, harvesting valuable pollen that could have been transferred to conspecific stigmas by other flower-visitors. To explore the relationship between wild-bees and their food-plants, the concept of pollen budget was developed. We quantified pollen production in the food-plant population and pollen consumption of wild-bee nests. A survey of the visitation by all flower-visitor taxa indicated that the degree of utilization (the fraction of the total pollen amount that is harvested and utilized by A. hattorfiana) varied from 12% to 80% among K. arvensis populations (N=26). The bee Andrena marginata utilized 44% of the pollen production in a population of Succisa pratensis. The pollen budget suggests that with an average flower-visitor diversity and abundance, 330 individuals of the food-plant K. arvensis are required to sustain a population of 20 A. hattorfiana ♀ (the approximate median natural population size). Based on a study of A. hattorfiana, considerable simplifications were proposed for the commonly used mark-recapture design for measuring wild-bee population size. For this species, population size estimated based on mark-recapture data was strongly correlated with the number of observations per survey-walk. The results suggest that large-scale surveys of solitary bee species can be simplified by performing survey-walks.

The pollen budget and the method proposed for estimating the size of bee populations have the potential to become valuable tools for monitoring and management of wild-bee populations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 33 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 210
Ecology, Andrena hattorfiana, Andrena marginata, Andrenidae, Knautia arvensis, limitation, oligolecty, pollen, pollination, solitary bee, specialist bee, Succisa pratensis, Ekologi
urn:nbn:se:uu:diva-7108 (URN)91-554-6634-6 (ISBN)
Public defence
2006-10-14, the lecture hall, Växtekologen, yellow building, Villavägen 14, Uppsala, 10:00
Available from: 2006-09-21 Created: 2006-09-21Bibliographically approved

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