Challenging the sustainability of urban beekeeping using evidence from Swiss cities

Urban beekeeping is booming, heightening awareness of pollinator importance but also raising concerns that its fast growth might exceed existing resources and negatively impact urban biodiversity. To evaluate the magnitude of urban beekeeping growth and its sustainability, we analysed data on beehives and available resources in 14 Swiss cities in 2012–2018 and modelled the sustainability of urban beekeeping under different scenarios of available floral resources and existing carrying capacities. We found large increases in hives numbers across all cities from an average 6.48 hives per km2 (3139 hives in total) in 2012 to an average 10.14 hives per km2 (9370 in total) in 2018 and observed that available resources are insufficient to maintain present densities of beehives, which currently are unsustainable.

Effects of Planted Pollinator Habitat On Bee Health And Interspecific Pathogen Detection

Shared resources can instigate pathogen spread due to large congregations of individuals in both natural and human modified resources. Of concern is the addition of pollinator habitat in conservation efforts as it attracts bees of various species, potentially instigating interspecific sharing of pathogens. Common pathogens have been documented across a wide variety of pollinators with shared floral resources instigating their spread in some, but not all, cases. To evaluate the impact of augmented pollinator habitat on bee health, we screened samples from eight bee species across three families against a panel of 9 pathogens using RT-qPCR. While we found that some habitat characteristics influenced pathogen detection, we found no evidence that pathogen detection in one bee species was correlated with pathogen detection in another. These findings suggest factors other than the habitat itself may be more critical in the dissemination of diseases among bee species. However, we found high levels of gut parasites in some bee species which may be of concern, such as Bombus pensylvanicus. Future monitoring of bee health at augmented pollinator habitat is needed to ensure pathogens do not build up over time to then spread within their communities.

Evaluation of Native and Nonnative Ornamentals as Pollinator Plants in Florida: I. Floral Abundance and Insect Visitation

Diverse floral resources impart immense value for pollinating insects of all types. With increasing popularity and demand for modern ornamental hybrids, cultivation by breeders has led to selection for a suite of traits such as extended bloom periods and novel colors and forms deemed attractive to the human eye. Largely understudied is pollinator preference for these new cultivars, as compared with their native congeners. To address this gap in understanding, 10 species of popular herbaceous flowering plants, commonly labeled as pollinator-friendly, were evaluated at two sites in Florida [U.S. Department of Agriculture (USDA) cold hardiness zones 8b and 9a] and across three seasons for their floral abundance and overall attractiveness to different groups of pollinating insects. Each genus, apart from pentas, encompassed a native and nonnative species. Native species included blanket flower (Gaillardia pulchella), lanceleaf coreopsis (Coreopsis lanceolata), pineland lantana (Lantana depressa), and scarlet sage (Salvia coccinea). Nonnative species included Barbican™ yellow-red ring blanket flower (G. aristata ‘Gaiz005’), Bloomify™ rose lantana (L. camara ‘UF-1011-2’), mysty salvia (S. longispicata ×farinacea ‘Balsalmysty’), Lucky Star® dark red pentas (Pentas lanceolata ‘PAS1231189’), ruby glow pentas (P. lanceolata ‘Ruby glow’) and Uptick™ Gold & Bronze coreopsis (Coreopsis × ‘Baluptgonz’). Flower-visiting insects were recorded during five-minute intervals in the morning and categorized into the following morpho-groups: honey bees, large-bodied bees (bumble and carpenter bees), other bees (small to medium-bodied native bees), butterflies/moths, and wasps. Floral abundance and pollinator visitation varied widely by season, location, and species. Of the plant species evaluated, nonnative plants produced nearly twice as many flowers as native plants. About 22,000 floral visitations were observed. The majority of visits were by native, small to medium-bodied bees (55.28%), followed by butterflies and moths (15.4%), large-bodied native bees (11.8%), wasps (10.0%), and honey bees (7.6%). Among plant genera, both native and nonnative coreopsis and blanket flower were most attractive to native, small to medium-bodied bees (e.g., sweat bees, leafcutter bees) with the greatest number of visitations occurring during the early and midmonths of the study (May–August). Across the study, butterflies and moths visited lantana more frequently than all other ornamentals evaluated, whereas pentas were most attractive to wasps. Large-bodied bees visited plants most frequently in May and June, primarily foraging from both native and nonnative salvia. While results from this study showed nominal differences between native and nonnative species in their ability to attract the studied pollinator groups, care should be taken to making similar assessments of other modern plant types.

Landscape Integrity Eclipses Local Effects of Floral Resource Availability on Bumble Bee (Bombus Spp.) Abundance in a Water-Limited Island Ecosystem

ContextHabitat loss threatens to exacerbate climate change impacts on pollinator communities, particularly in Mediterranean-type ecosystems where late season floral resource availability is limited by seasonal drought. While gardens have been found to supplement floral resources in water-limited urban landscapes, less is known about the role of natural habitat diversity in sustaining late season floral resources in more intact landscapes. ObjectivesWe investigated the importance of habitat integrity and diversity for bumble bees in a water-limited ecosystem, observing bumble bee community response to seasonal drought across gradients of disturbance and soil moisture.MethodsWe applied hierarchical models to estimate the effects of local site conditions versus landscape scale estimates of matrix habitat on bumble bee abundance. Floral resources, soil moisture, and other environmental variables were sampled along randomly distributed belt transects. Geospatial estimates of matrix habitat were derived from terrestrial ecosystem data. Bumble bees were sampled with blue vane traps.ResultsIn the late season we found that modified wet areas supported more floral resources and bumble bee workers as compared to dry semi-natural environments. Wetlands also supported more late season floral resources and bumble bee workers, though the latter effect was not significant. Despite higher levels of late season floral resources in modified wet environments, modified matrix habitat was negatively associated, and natural matrix positively associated, with workers in June and late-flying queens in July and August. We also detected differences in bumble bee community composition in disturbed versus undisturbed environments.ConclusionsThough wet modified habitats sustained the highest levels of late season floral resource availability and worker abundances in our study, bumble bee diversity and abundance were limited primarily by the availability of natural matrix habitat at the landscape scale. The conservation of natural habitat integrity and diversity can help support critical nesting and foraging habitat, and should be prioritized in efforts to foster the resilience of pollinator communities.

Nest aggregations of wild bees and apoid wasps in urban pavements: a street life to be promoted in urban planning

In the last 10 years, knowledges of wild bees and apoid wasps community dynamics have gained interest in urban ecology focusing on the availability of floral resources in cities. Although understudied, the urban environment impacts the conditions of their nesting sites. Recent observations in the Brussels-Capital Region (Belgium) showed that urban pavements can be a novel nesting opportunity for Hymenoptera ground-nesting species such as wild bees and apoid wasps. Here, using citizen science, we investigated the richness of ground-nesting species living under urban pavements, the preferences of the sidewalk joint size related to ground-nesting species size and for sidewalk type or for soils texture under the pavements on the nesting site selection. A total of 22 species belonging to 10 Hymenoptera families of wild bees and digger wasps with their associated kleptoparasites were identified on 89 sites in Brussels. Sandstone setts or concrete slabs with an unbound joint size around 1 cm were found to be best suitable urban pavements for the ground-nesting species. The soil texture under the pavement was highly sandy among our samples. Finally, we also suggest engineering management guidelines to support bee and wasp species nesting under urban pavement in highly urbanized areas. Such observations pave the way for much research in the field of urban ecology to conceive multifunctional pavement promoting biodiversity.

Behavior, ecology and territory of the chestnut-bellied hummingbird, Saucerottia castaneiventris, in the xerophytic vegetation of the Chicamocha canyon of Colombia

The Chestnut-bellied Hummingbird Saucerottia castaneiventris is an endemic hummingbird of Colombia, currently categorized as Near Threatened (NT) globally and as Vulnerable (VU) in Colombia. We characterize the territorial defense and foraging behaviors of S. castaneiventris hummingbird during different seasons of the year, and we determined the size of the S. castaneiventris territory and its relationship with floral abundance at different times of the year. We made four field trips between 2008 and 2009 and registered 19 individuals from S. castaneiventris. Of these, 10 were in the rainy periods, distributed in five territories (one male and one female for each). Eight were in the dry period (July), distributed in four territories. And one individual was in the dry period of February, which did not settle in any of the identified territories. Territorial defense occupied a large part of species’ time. The nectar drinking, and insect hunting were the most frequent activities. The most common floral resources were Opuntia dillenii, Tillandsia sp. and Aloe vera. The hummingbirds Chlorostilbon gibsoni and Doryfera ludoviciae shared habitats with S. castaneiventris and there were fluctuations in encounter rates between the seasons (C. gibsoni ER: 20–7.5 and D. ludoviciae and ER: 0.0–2.5). Territories ranged between 1800 and 3800 m2 for the dry season and between 1500 and 6500 m2 for the rainy season. Our results provided primary information on the ecology of S. castaneiventris and form the basis for the formulation of conservation strategies for the species and for its habitats..

Pollinator enhancement in agriculture: comparing sown flower strips, hedges and sown hedge herb layers in apple orchards

In intensive agricultural landscapes semi-natural habitats for pollinators are often limited, although willingness to establish pollinator habitat is increasing among farmers. A common pollinator enhancement measure is to provide flower strips, but existent or improved hedgerows might be more effective. In this study, we compare the effectiveness of three pollinator enhancement measures at edges of conventional apple orchards: (i) perennial flower strips, (ii) existent hedgerows, and (iii) existent hedgerows complemented with a sown herb layer. We used orchard edges without any enhancement as control. The study took place over three consecutive years in Southern Germany. Wild bee abundance and species richness were highest in flower strips followed by improved hedges. Hoverflies were also most abundant in flower strips, but not more species rich than at control sites. Wild bee but not hoverfly community composition differed between control and enhancement sites. The overall pollinator community included only few threatened or specialized species. Flower abundance was the main driver for wild bee diversity, whereas hoverflies were largely unaffected by floral resources. Pollinator enhancement had neither an effect on the abundance or species richness within the orchards nor on apple flower visitation. Perennial flower strips seem most effective to enhance wild bees in intensive agricultural landscapes. Additionally, flower-rich hedgerows should be promoted to complement flower strips by extending the flowering period and to increase connectivity of pollinator habitat in agricultural landscapes.

DNA metabarcoding reveals broadly overlapping diets in three sympatric North American hummingbirds

ABSTRACT Hummingbirds, a highly diverse avian family, are specialized vertebrate pollinators that feed upon carbohydrate-rich nectar to fuel their fast metabolism while consuming invertebrates to obtain protein. Previous work has found that morphologically diverse hummingbird communities exhibit higher diet specialization on floral resources than morphologically similar hummingbird communities. Due to the difficulties of studying avian diets, we have little understanding whether hummingbirds show similar patterns with their invertebrate prey. Here, we use DNA metabarcoding to analyze floral and invertebrate diets of 3 species of sympatric North American hummingbirds. We collected fecal samples from 89 Anna’s (Calypte anna), 39 Black-chinned (Archilochus alexandri), and 29 Calliope (Selasphorus calliope) hummingbirds in urban and rural localities as well as across an elevational gradient from sea level to 2,500 meters above sea level in California, USA. We found hummingbirds showed high dietary overlap in both invertebrate and plant resources, with few invertebrate and plant families common to most individuals and many families found in only a few individuals. Chironomidae was the most common invertebrate family across all species, and Rosaceae and Orobanchaceae were the most common plant families. Anna’s Hummingbirds had significantly higher invertebrate diet diversity than Black-chinned Hummingbirds when found at the same sites, but we found no difference in plant diet diversity among any of the 3 species. Hummingbirds in urban sites had higher plant diet diversity than in rural sites, but we found no effect of elevation on dietary richness. Our study shows how DNA metabarcoding can be used to non-invasively investigate previously unknown life-histories of well-studied birds, lending insight to community structure, function, and evolution.

FLORAL BIOLOGY AND BEEKEEPING POTENTIAL OF Croton heliotropiifolius KUNTH (EUPHORBIACEAE) AT SEMI ARID REGION, BRAZIL1

ABSTRACT The aim of the present study was to determine the beekeeping potential of Croton heliotropiifolius Kunth (Euphorbiaceae) based on flowering strategy, floral characteristics, available floral resources, and the individuals frequencies and foraging activities of Apis mellifera L. on its flowers in Fazenda Ingazeira, Brazil. Each C. heliotropiifolius plant possessed inconspicuous diclinous flowers clustered into 560 ± 60 dense terminal inflorescences containing 59 ± 12 pistillate and 160 ± 26 staminate flowers. Although both types of flowers produced nectar (pistillate: 2.8 ± 0.8 μL ; staminate: 0.3 ± 0.06 μL ), A. mellifera workers mostly visited staminate flowers (98%) during the peak visitation period (08:00-11:00 h). Moreover, during the foraging period, each plant produced approximately 5.376 × 10 8 pollen grains, ensuring approximately 33 visitation cycles from a colony of A mellifera workers that picked up an average of 405 pollen grains per visit per flower. Further, C. heliotropiifolius showed an annual cornucopia flowering strategy with high flower production for five months, which is an important characteristic that ensures floral resource availability in the environment. These findings suggest that C. heliotropiifolius has a great potential for apiculture in this region.