ABSTRACTLand use change threatens global biodiversity and compromises ecosystem functions, including pollination and food production. Reduced taxonomic α‐diversity is often reported under land use change, yet the impacts could be different at larger spatial scales (i.e., γ‐diversity), either due to reduced β‐diversity amplifying diversity loss or increased β‐diversity dampening diversity loss. Additionally, studies often focus on taxonomic diversity, while other important biodiversity components, including phylogenetic diversity, can exhibit differential responses. Here, we evaluated how agricultural and urban land use alters the taxonomic and phylogenetic α‐, β‐, and γ‐diversity of an important pollinator taxon—bees. Using a multicontinental dataset of 3117 bee assemblages from 157 studies, we found that taxonomic α‐diversity was reduced by 16%–18% in both agricultural and urban habitats relative to natural habitats. Phylogenetic α‐diversity was decreased by 11%–12% in agricultural and urban habitats. Compared with natural habitats, taxonomic and phylogenetic β‐diversity increased by 11% and 6% in urban habitats, respectively, but exhibited no systematic change in agricultural habitats. We detected a 22% decline in taxonomic γ‐diversity and a 17% decline in phylogenetic γ‐diversity in agricultural habitats, but γ‐diversity of urban habitats was not significantly different from natural habitats. These findings highlight the threat of agricultural expansions to large‐scale bee diversity due to systematic γ‐diversity decline. In addition, while both urbanization and agriculture lead to consistent declines in α‐diversity, their impacts on β‐ or γ‐diversity vary, highlighting the need to study the effects of land use change at multiple scales.

While an increasing number of studies indicate that the range, diversity and abundance of many wild pollinators has declined, the global area of pollinator-dependent crops has significantly increased over the last few decades. Crop pollination studies to date have mainly focused on either identifying different guilds pollinating various crops, or on factors driving spatial changes and turnover observed in these communities. The mechanisms driving temporal stability for ecosystem functioning and services, however, remain poorly understood. Our study quantifies temporal variability observed in crop pollinators in 21 different crops across multiple years at a global scale. Using data from 43 studies from six continents, we show that (i) higher pollinator diversity confers greater inter-annual stability in pollinator communities, (ii) temporal variation observed in pollinator abundance is primarily driven by the three-most dominant species, and (iii) crops in tropical regions demonstrate higher inter-annual variability in pollinator species richness than crops in temperate regions. We highlight the importance of recognizing wild pollinator diversity in agricultural landscapes to stabilize pollinator persistence across years to protect both biodiversity and crop pollination services. Short-term agricultural management practices aimed at dominant species for stabilizing pollination services need to be considered alongside longer term conservation goals focussed on maintaining and facilitating biodiversity to confer ecological stability.

Many farmers are facing high economic risks if pollinator declines continue or temporal and spatial variation in wild bee communities cause reduced pollination services. Co-flowering crops might compete for pollinators, while they also might facilitate the delivery of pollination services. This rarely studied topic is of particular interest with respect to the foraging decisions of bees from different functional groups and when more sparsely and mass-flowering crops are in bloom at the same time. The abundance of honey bees, bumble bees and solitary bees in strawberry fields was quantified with transect walks along a gradient of oilseed rape (OSR) availability (product of OSR land cover and temporally changing OSR flower cover). We established a pollination experiment with pollination treatments (open-, wind- and self-pollination) to study the effects of insect pollination on strawberry fruit weight and quality. Changes in OSR availability exhibited contrasting effects on social versus solitary bees in strawberry fields. Bumble bees and honey bees were less abundant in strawberry fields when OSR availability was high, whereas solitary bees were facilitated. With more strawberry flowers, we found more bees in general. When flowers were open-pollinated, they resulted in heavier fruits with better commercial grades compared to wind- and self-pollinated flowers. A higher bee abundance enhanced the strawberry fruit weight and quality but depended on flower order and variety. Synthesis and applications. Sparsely flowering crops may compete with mass-flowering crops for social bee pollinators, while solitary pollinators in the field might be evenly facilitated. To ensure best fruit weight and quality, it can be beneficial to support bee abundance in the field. While some social and solitary bee species can be managed for pollination services, wild bees, in particular solitary species, should be conserved and promoted for stable crop pollination services in dynamic agricultural landscapes.

The demand for crop pollination is increasing and honey bees are frequently used, in particular as wild pollinators are in decline. Temporal and spatial variation of flower resources affects foraging decisions of wild and honey bees. To optimise crop pollination management a better understanding of potential competition for pollinators in mass- and minor-flowering crops is needed. We combined waggle dance decoding, pollen load analysis and field surveys to identify the habitat preferences and pollen use of honey bees in response to spatio-temporal changes in resource availability. Observation hives were placed on the edge of eleven fields of blooming strawberries (mean 2.24 ha) located in landscapes with different amounts of oilseed rape (OSR), semi-natural habitats (SNH) and apple trees in Germany. In addition, we surveyed honey bees and wild bees in strawberry fields. Honey bee dances more often indicated strawberry, OSR fields and SNH than expected given their landscape-wide areas. Honey bees collected on average 7.9 % strawberry, 49.0 % OSR, 30.2 % Pyrus type (e.g. apple) and 12.9 % other pollen types. The mean honey bee foraging distance was 740 m, and decreased with OSR availability. In the observation hives, dances for strawberry fields were not directly affected by OSR availability or SNH land cover. But large amounts of OSR reduced overall honey bee and bumble bee abundance in strawberry fields, while solitary bees were unaffected. Bumble bees were most abundant in strawberry fields (54.1%) and together with solitary bees (19.7%) they represented about 75.0% of the observed bees. Minor-flowering strawberry fields represent a preferred resource for honey bees, especially for small colonies as indicated by decoding of waggle dances. However, the availability of more attractive OSR and local strawberry flower cover moderates the abundance of social bees (honey bees and bumble bees) in strawberry fields while other wild bees were less affected. Hence, we conclude that wild bee conservation plays a major role for strawberry pollination. If pollination services by solitary bees are limited, small honey bee hives can be used scrupulously to supplement pollination services in strawberries.

Worldwide pollinator declines lead to pollination deficits in crops and wild plants, and managed bees are frequently used to meet the increasing demand for pollination. However, their foraging can be affected by flower availability and colony size. We investigated how mass-flowering oilseed rape (OSR) can influence the pollen resource use of small and large honey bee (Apis mellifera L.) and bumble bee (Bombus terrestris L.) colonies. Colonies were placed adjacent to strawberry fields along a gradient of OSR availability in the landscapes. We used ITS2 metabarcoding to identify the pollen richness based on ITS2 amplicon sequencing and microscopy for quantification of target pollen. Bumble bees collected pollen from more different plant genera than honey bees. In both species, strawberry pollen collection decreased with high OSR availability but was facilitated by increasing strawberry flower cover. Colony size had no effect. The relationship between next-generation sequencing-generated ITS2 amplicon reads and microscopic pollen counts was positive but pollen type-specific. Bumble bees and, to a lesser degree, honey bees collected pollen from a wide variety of plants. Therefore, in order to support pollinators and associated pollination services, future conservation schemes should sustain and promote pollen plant richness in agricultural landscapes. Both bee species responded to the availability of flower resources in the landscape. Although honey bees collected slightly more strawberry pollen than bumble bees, both can be considered as crop pollinators. Metabarcoding could provide similar quantitative information to microscopy, taking into account the pollen types, but there remains high potential to improve the methodological weaknesses.

Bumble bees are important crop pollinators and provide important pollination services to their respective ecosystems. Their pollen diet and thus food preferences can be characterized through nucleic acid sequence analysis. We present ITS2 amplicon sequence data from pollen collected by bumble bees. The pollen was collected from six different bumble bee colonies that were placed in independent agricultural landscapes. We compared next-generation (Illumina), i.e., short-read, and third-generation (Nanopore), i.e., MinION, sequencing techniques. MinION data were preprocessed using traditional and Nanopore specific tools for comparative analysis and were evaluated in comparison to short-read sequence data with conventional processing. Based on the results, the dietary diary of bumble bee in the studied landscapes can be identified. It is known that short reads generated by next-generation sequencers have the advantage of higher quality scores while Nanopore yields longer read lengths. We show that assignments to taxonomic units yield comparable results when querying against an ITS2-specific sequence database. Thus, lower sequence quality is compensated by longer read lengths. However, the Nanopore technology is improving in terms of data quality, much cheaper, and suitable for portable applications. With respect to the studied agricultural landscapes we found that bumble bees require higher plant diversity than only crops to fulfill their foraging requirements.

Data and R Skript from Bänsch et al. 2020, Molecular Ecology

Intensified agriculture increasingly threatens wild and managed bees by promoting landscape uniformity and reducing floral resource availability whereas urban areas can provide continuous floral resources within green spaces and private gardens. Mass-flowering events of crops and trees, such as lime trees ( spp.), can provide ample floral resources but only for short time periods. Using waggle dance decoding, pollen analysis and bee abundance recordings, we investigated the temporal shift in honeybee foraging behaviour in response to lime tree mass-flowering. Honeybees in urban areas extended their foraging range during lime tree flowering. Foraging behaviour of honeybees in rural areas did not change to such an extent and honeybees foraged in sown flower strips. Our results suggest that honeybees optimize their foraging behaviour to exploit highly rewarding resources instead of extending foraging ranges in times of floral resource scarcity.

Forty-four percent of Europe’s terrestrial surface is covered with agricultural land. Thus, agriculture strongly influences Europe’s environment, including ecological functions and processes.

1. The land-sharing versus land-sparing debate recently stagnated, lacking an integrating perspective in agricultural landscapes as well as consideration of ecosystem services. Here, we argue that land-sharing (i.e. wildlife-friendly farming systems) and land-sparing (i.e. separation of high-yielding agriculture and natural habitats) are not mutually exclusive, as both are needed to balance management needs for the multifunctionality of agricultural landscapes. 2. Land-sharing promotes ecosystem services in agricultural settings, thereby allowing for environmentally friendly production. Land set aside in protected areas by land-sparing is crucial for conservation of those species that are incompatible with agriculture. 3. Importantly, as species move throughout the landscape and exploit different habitats, increased connectivity between environmentally friendly managed and protected areas is needed to (a) promote spillover of ecosystem service providers from land-sharing/-sparing measures to agricultural production and rescue ser-vice-providing species from extinction in hostile areas, (b) to facilitate immigration and counteract possible extinctions in spared habitats and (c) to conserve response diversity of species communities for ensuring resilience of ecosystem services in changing environments. 4. In conclusion, the successful management of multifunctional landscapes requires the combination of context-specific land-sharing and land-sparing measures within spatially well-connected landscape mosaics, resulting in land-sharing/-sparing connectivity landscapes.

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

Many farmers are facing high economic risks if pollinator declines continue or temporal and spatial variation in wild bee communities cause reduced pollination services.Coflowering crops might compete for pollinators, while they also might facilitate the delivery of pollination services.This rarely studied topic is of particular interest with respect to the foraging decisions of bees from different functional groups and when more sparsely and mass-flowering crops are in bloom at the same time.The abundance of honey bees, bumble bees and solitary bees in strawberry fields was quantified with transect walks along a gradient of oilseed rape (OSR) availability (product of OSR land cover and temporally changing OSR flower cover).We established a pollination experiment with pollination treatments (open-, wind-and self-pollination) to study the effects of insect pollination on strawberry fruit weight and quality.Changes in OSR availability exhibited contrasting effects on social versus solitary bees in strawberry fields.Bumble bees and honey bees were less abundant in strawberry fields when OSR availability was high, whereas solitary bees were facilitated.With more strawberry flowers we found more bees in general.When flowers were open-pollinated they resulted in heavier fruits with better commercial grades compared to wind-and self-pollinated flowers.A higher bee abundance enhanced the strawberry fruit weight and quality but depended on flower order and variety.Synthesis and applications.Sparsely flowering crops may compete with mass-flowering crops for social bee pollinators while solitary pollinators in the field might be even facilitated.To ensure best fruit weight and quality it can be beneficial to support bee abundance in the field.While some social and solitary bee species can be managed for pollination services, wild bees, in particular solitary species, should be conserved and promoted for stable crop pollination services in dynamic agricultural landscapes.