Effects of grazing intensity on pollinator abundance and diversity, and on pollination services
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Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Entomological Society
Abstract
1. Pollinating insects provide important ecosystem services and are influ-
enced by the intensity of grazing. Based on the Intermediate Disturbance Hypothesis
(IDH), pollinator diversity is expected to peak at intermediate grazing intensities. How-
ever, this hump-shaped relationship is rarely found.
2. The effect of grazing intensity was tested on flower cover, on the abundance and
richness of bees, hoverflies and bee flies, and on pollination services to early-flowering
bee-pollinated Asphodelus ramosus L. For that, we used data on 11 plant–pollinator
phryganic communities from Lesvos Island (Greece) widely differing in grazing
intensities.
3. Flower abundance and richness showed hump-shaped relationships with grazing
intensity. Grazing affected the abundance and richness of bees and hoverflies directly and
also indirectly, through changes in the flower community. Grazing influenced directly the
richness but not the abundance of bee flies. Overall, pollinator abundance and richness
showed hump-shaped relationships with grazing intensity, but variations in strength
(hoverfly abundance) and direction (bee community) of the effect appeared along the
season. Early in the season, grazing increased bee abundance but decreased richness,
resulting in increased pollen limitation in A. ramosus.
4. The effects of grazing on pollinators vary with the intensity of the disturbance,
generally supporting the IDH, and the timing of land-use activities may influence
pollination services. Management strategies should include moderate grazing levels to
preserve overall diversity in this area, however, the conservation of particular early bee
or bee-pollinated species may benefit from reduced grazing in early spring.
Description
Journal Article
Keywords
Bee flies, Bees, Hoverflies, Intermediate Disturbance Hypothesis, Mediterranean phryganic communities, Pollen limitation, Species richness
Citation
DOI: 10.1111/een.12310