TY - BOOK
T1 - Wild Bee Community Composition and Foraging Behaviour in Commercial Strawberries
T2 - Effects of Region, Field-Margins and Cultivars
AU - Ahrenfeldt, Erica Juel
PY - 2015
Y1 - 2015
N2 - The agricultural value of wild bees is their contribution to crop pollination and studies have shown
that abundance, species richness and functional diversity of bees can increase yield and quality of
flowering crops. Wild bee pollination services thus carry great value regardless of the presence of
managed honeybees. Among other factors, the functional diversity of wild bees increases with
species richness of the bees present and the variation in species body-size. Globally, agricultural
intensification with increased field sizes and habitat loss and fragmentation has led to a severe
reduction in diversity and abundance of wild bees as a result of reduced and scattered food and
nesting-resources. Agriculture is the dominant type of land-use in Denmark and 66 % of the Danish
landscape is farmland. However, little is known about the diversity of wild bees and associated
pollination services in Denmark despite the fact that value of bee pollination of cultured crops is
estimated to approach 800 million DKK.
This thesis explores how regional, landscape and local differences affect biodiversity and
abundance of wild bees (paper I and II) and wild bee foraging behaviour in terms of spatial
distribution in the field (II) and the influence of crop variety on preference for pollen and nectar
(III). Strawberry (Fragaria x ananassa DUCH.) was used as a model crop for field studies (I, II,
III). Strawberry yield and quality are both considerably increased from insect pollination and
strawberry is grown throughout Denmark and under widespread cultivation in the rest of the world.
A review study (IV) of the literature on wild bees and their pollination services in flowering crops
make up the final part of the thesis. The review study aimed to assess how wild bees may respond to
landscape parameters based on their biology, in particular diet, habitat requirements and sociality.
At a regional scale (I) bee activity-density and species richness was higher in Denmark and
Germany compared to South and Mid Norway, whereas the mean bee body size was higher in
South- and Mid-Norway. At landscape scale (II) hedges and small clusters of trees positively
affected activity-density of bees at scales from 100 m - 2000 m from where the bees were trapped,
which shows the conservation value these habitats represent for wild bees in the agricultural land.
Forest negatively affected activity-density at all spatial scales possibly due to the low biodiversity
offered by many commercially driven, single species, Danish forests. At field scale (I) bee species
richness was higher in field margins compared to field centres but there was no difference between
centre and margin in body-size or activity-density. Sampling time had an effect on wild bee
community composition with higher activity-density and species richness in late May and late June
than in early and mid-June (II). Results thus indicate that functional diversity of visiting wild bee
assemblages in strawberry differs depending on the spatial and time scale in consideration. There
are indications that solitary bees and bumblebees may be affected differently both at landscape and
field scale, with solitary bees having a stronger response than bumblebees at small spatial scales.
Most of the species and individuals sampled in and near strawberry fields were ground-nesting
polylectic solitary species that are known to forage in the family Rosaceae, to which strawberry
belong, which indicate that the bees sampled are a source of pollination in strawberries (I, II).
Furthermore, the high proportion of polylectic bees found in Danish strawberry fields indicate that
an adaptation to a landscape with fragmented resources may already have taken place in the areas
sampled. Paper I and III showed that limitations on foraging ability and different foraging needs can
drive different visitation patterns in a flowering crop. The review study (IV) found variation in
results from different studies on the effects of farming practice and landscape on wild bees.
Ecological and life-history differences between bees may be what the drives this variation. Results
from all three experimental papers (I, II, III) support this conclusion and future studies may
therefore benefit from considering these differences between bee species.
AB - The agricultural value of wild bees is their contribution to crop pollination and studies have shown
that abundance, species richness and functional diversity of bees can increase yield and quality of
flowering crops. Wild bee pollination services thus carry great value regardless of the presence of
managed honeybees. Among other factors, the functional diversity of wild bees increases with
species richness of the bees present and the variation in species body-size. Globally, agricultural
intensification with increased field sizes and habitat loss and fragmentation has led to a severe
reduction in diversity and abundance of wild bees as a result of reduced and scattered food and
nesting-resources. Agriculture is the dominant type of land-use in Denmark and 66 % of the Danish
landscape is farmland. However, little is known about the diversity of wild bees and associated
pollination services in Denmark despite the fact that value of bee pollination of cultured crops is
estimated to approach 800 million DKK.
This thesis explores how regional, landscape and local differences affect biodiversity and
abundance of wild bees (paper I and II) and wild bee foraging behaviour in terms of spatial
distribution in the field (II) and the influence of crop variety on preference for pollen and nectar
(III). Strawberry (Fragaria x ananassa DUCH.) was used as a model crop for field studies (I, II,
III). Strawberry yield and quality are both considerably increased from insect pollination and
strawberry is grown throughout Denmark and under widespread cultivation in the rest of the world.
A review study (IV) of the literature on wild bees and their pollination services in flowering crops
make up the final part of the thesis. The review study aimed to assess how wild bees may respond to
landscape parameters based on their biology, in particular diet, habitat requirements and sociality.
At a regional scale (I) bee activity-density and species richness was higher in Denmark and
Germany compared to South and Mid Norway, whereas the mean bee body size was higher in
South- and Mid-Norway. At landscape scale (II) hedges and small clusters of trees positively
affected activity-density of bees at scales from 100 m - 2000 m from where the bees were trapped,
which shows the conservation value these habitats represent for wild bees in the agricultural land.
Forest negatively affected activity-density at all spatial scales possibly due to the low biodiversity
offered by many commercially driven, single species, Danish forests. At field scale (I) bee species
richness was higher in field margins compared to field centres but there was no difference between
centre and margin in body-size or activity-density. Sampling time had an effect on wild bee
community composition with higher activity-density and species richness in late May and late June
than in early and mid-June (II). Results thus indicate that functional diversity of visiting wild bee
assemblages in strawberry differs depending on the spatial and time scale in consideration. There
are indications that solitary bees and bumblebees may be affected differently both at landscape and
field scale, with solitary bees having a stronger response than bumblebees at small spatial scales.
Most of the species and individuals sampled in and near strawberry fields were ground-nesting
polylectic solitary species that are known to forage in the family Rosaceae, to which strawberry
belong, which indicate that the bees sampled are a source of pollination in strawberries (I, II).
Furthermore, the high proportion of polylectic bees found in Danish strawberry fields indicate that
an adaptation to a landscape with fragmented resources may already have taken place in the areas
sampled. Paper I and III showed that limitations on foraging ability and different foraging needs can
drive different visitation patterns in a flowering crop. The review study (IV) found variation in
results from different studies on the effects of farming practice and landscape on wild bees.
Ecological and life-history differences between bees may be what the drives this variation. Results
from all three experimental papers (I, II, III) support this conclusion and future studies may
therefore benefit from considering these differences between bee species.
UR - https://rex.kb.dk/primo-explore/fulldisplay?docid=KGL01009155026&context=L&vid=NUI&search_scope=KGL&isFrbr=true&tab=default_tab&lang=da_DK
M3 - Ph.D. thesis
BT - Wild Bee Community Composition and Foraging Behaviour in Commercial Strawberries
PB - Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
ER -