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Turnover in bee species composition and functional trait distributions between seasons in a tropical agricultural landscape
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
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Number of Authors: 5
2015 (English)In: Agriculture, Ecosystems & Environment, ISSN 0167-8809, E-ISSN 1873-2305, Vol. 211, 185-194 p.Article in journal (Refereed) Published
Abstract [en]

A comprehensive understanding of how spatial variation across landscapes regulates local abundances and species richness also needs to consider possible temporal changes in such relationships. In many tropical areas, the contrast between dry and rainy season is pronounced and the types and distributions of the main floral resources differ (herbs vs trees). This shift in resources could result in different pollinator abundances, species richness and trait compositions between seasons, as well as in how these components are spatially distributed. We compared the bee species composition between dry and rainy season in an agricultural mosaic landscape in southwestern Ethiopia, and analyzed it in relation to forest cover. We sampled bees for 67 days in the dry season and 86 days in the rainy season with pan and vane traps in 28 homegardens covering a gradient from low to high tree cover in the surrounding area. We found a clear shift in species composition between seasons, with more small bee species and more below-ground nesting bees in the rainy season compared to the dry season. The distribution of height at which the bees were foraging shifted between seasons with a higher proportion of the bees foraging at tree level in the dry season. Bee abundance and richness were generally positively affected by higher forest cover surrounding the homegardens, but there were no clear interaction effects between seasons, in contrast to our hypothesis. The clear turnover in species composition between seasons and the positive effect of forest cover show that mechanisms acting both at spatial and temporal scales are important in regulating local bee communities.

Place, publisher, year, edition, pages
2015. Vol. 211, 185-194 p.
Keyword [en]
Ethiopia, Functional trait, Pollinator, Spatial pattern, Temporal dynamic
National Category
Agricultural Science, Forestry and Fisheries Biological Sciences Earth and Related Environmental Sciences
Research subject
Plant Ecology
URN: urn:nbn:se:su:diva-122233DOI: 10.1016/j.agee.2015.06.010ISI: 000362049800021OAI: diva2:866635
Available from: 2015-11-03 Created: 2015-10-28 Last updated: 2016-02-12Bibliographically approved
In thesis
1. The impact of forest on pest damage, pollinators and pollination services in an Ethiopian agricultural landscape
Open this publication in new window or tab >>The impact of forest on pest damage, pollinators and pollination services in an Ethiopian agricultural landscape
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The distribution of wild biodiversity in agroecosystems affect crop performance and yield in various ways. In this thesis I have studied the impact of wild biodiversity, in terms of trees and forest structures, on crop pests, pollinators and the pollination services provided in a heterogeneous landscape in southwestern Ethiopia. 

Coffee, Coffea arabica, is a forest shrub native to Ethiopia and is grown in most wooded areas in the landscape where I conducted my studies. Wild coffee is still found in remote parts of the forests in the landscape. For my first paper, I surveyed pest damage on coffee in coffee forest sites, where some sites were situated in continuous forest and some in isolated forest patches. I found the variation in pest damage frequency to mainly be among coffee plants within a site, rather than among sites, which indicates the importance of local processes. However, some pests were clearly connected to the forest habitat, such as the olive baboon.

In my second study, I surveyed pollinators visiting coffee flowers across a gradient of shade-tree structures. I found the semi-wild honeybee to be the dominating flower visitor. The abundance of the honeybee was not related to shade-tree structures, but to amount of coffee flower resources in the site. On the other hand, other pollinators, which included other bee species and hoverflies, were positively affected by more shade trees in the site.

In my third study I investigated how the forest cover affected local bee communities in the agricultural landscape. Moreover, I investigated if this relationship differed between the dry and rainy season. The distribution of food resources for bees changes between the seasons, which may affect the bees. Most trees, fruit trees and coffee, which are patchy resources, flowers in the dry season, whereas most herbs and annual crops, which are more evenly spread resources, flowers during the rainy season. I found a clear turnover in bee species composition between the dry and rainy season, with more mobile species in the dry season. Increased forest cover in the surrounding landscape had a positive impact on bee abundance and species richness. However, the impact did not change between seasons.

In my fourth study I evaluated the pollination success and pollen limitation of a common oil crop in the landscape in relation to forest cover. I found severe pollen limitation across the landscape, which may be related to the observed low bee abundances. The pollen limitation was not related to surrounding forest cover.

In conclusion, I have found the forest and wooded habitats to impact several mobile animals and pathogens in our study landscape, which in turn affect people. However, there is large complexity in nature and general relationships between forest structures and all crop related organisms may be unlikely to find. Various species are dependent on different resources, at different spatial scales and are interacting with several other species. To develop management strategies for increased pollination services, for reduced pest damage or for conservation in the landscape, more species-specific knowledge is needed.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2016. 48 p.
agroforestry, Apoidea, Coffea arabica, crop pests, Ethiopia, forest cover, landscape ecology, moist afromontane forests, pollination, species composition, tropical agriculture
National Category
Research subject
Plant Ecology
urn:nbn:se:su:diva-126669 (URN)978-91-7649-354-0 (ISBN)
Public defence
2016-04-01, Vivi Täckholmsalen, NPQ-huset, Svante Arrhenius väg 20 A, Stockholm, 10:00 (English)
Sida - Swedish International Development Cooperation Agency, SWE-2009-134Swedish Research Council Formas, 229-2009-991

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2016-03-09 Created: 2016-02-10 Last updated: 2016-02-26Bibliographically approved

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Samnegård, UlrikaHambäck, Peter A.Hylander, Kristoffer
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