title: Pollinator communities in strawberry crops - variation at multiple spatial scales.
abstract: Predicting potential pollination services of wild bees in crops requires knowledge of their spatial distribution within fields. Field margins can serve as nesting and foraging habitats for wild bees and can be a source of pollinators. Regional differences in pollinator community composition may affect this spill-over of bees. We studied how regional and local differences affect the spatial distribution of wild bee species richness, activity-density and body size in crop fields. We sampled bees both from the field centre and at two different types of semi-natural field margins, grass strips and hedges, in 12 strawberry fields. The fields were distributed over four regions in Northern Europe, representing an almost 1100 km long north-south gradient. Even over this gradient, daytime temperatures during sampling did not differ significantly between regions and did therefore probably not impact bee activity. Bee species richness was higher in field margins compared with field centres independent of field size. However, there was no difference between centre and margin in body-size or activity-density. In contrast, bee activity-density increased towards the southern regions, whereas the mean body size increased towards the north. In conclusion, our study revealed a general pattern across European regions of bee diversity, but not activity-density, declining towards the field interior which suggests that the benefits of functional diversity of pollinators may be difficult to achieve through spill-over effects from margins to crop. We also identified dissimilar regional patterns in bee diversity and activity-density, which should be taken into account in conservation management.
authors.affiliation: Department of Plant and Environmental Sciences,Faculty of Science,University of Copenhagen,Thorvaldsensvej 40,1871 Frederiksberg C,Denmark.
authors.forename: E J
authors.initials: EJ
authors.lastname: Ahrenfeldt
authors.affiliation: Agroecology,Georg-August-University Göttingen,Grisebachstraße 6,37077 Göttingen,Germany.
authors.forename: B K
authors.initials: BK
authors.lastname: Klatt
authors.affiliation: Department of Plant and Environmental Sciences,Faculty of Science,University of Copenhagen,Thorvaldsensvej 40,1871 Frederiksberg C,Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Arildsen
authors.affiliation: Norwegian Institute for Agricultural and Environmental Research (Bioforsk),Høgskoleveien 7,1432 Ås,Norway.
authors.forename: N
authors.initials: N
authors.lastname: Trandem
authors.affiliation: Department of Biology,Lund University,Ecology building,223 62 Lund,Sweden.
authors.forename: G K S
authors.initials: GK
authors.lastname: Andersson
authors.affiliation: Agroecology,Georg-August-University Göttingen,Grisebachstraße 6,37077 Göttingen,Germany.
authors.forename: T
authors.initials: T
authors.lastname: Tscharntke
authors.affiliation: Department of Biology,Lund University,Ecology building,223 62 Lund,Sweden.
authors.forename: H G
authors.initials: HG
authors.lastname: Smith
authors.affiliation: Department of Plant and Environmental Sciences,Faculty of Science,University of Copenhagen,Thorvaldsensvej 40,1871 Frederiksberg C,Denmark.
authors.forename: L
authors.initials: L
authors.lastname: Sigsgaard
mesh_terms: D063147:Animal Distribution; D000818:Animals; D001516:Bees / Q000502:physiology*; D049628:Body Size; D005060:Europe; D031985:Fragaria / Q000502:physiology*; D054817:Pollination / Q000502:physiology*
keywords: activity-density; body size; pollination; strawberry; wild bee diversity