No abstract

Effective pollination is a complex phenomenon determined by the outcome of the interaction between pollen transfer and a plants' pollinator dependency, yet most studies investigate pollinator effectiveness without consideration of plant mating system differences. We investigated pollinator effectiveness in three types of blueberry that differed in their degree of pollinator dependency as measured by plant mating system: two self‐compatible highbush cultivars and one partially self‐incompatible rabbiteye cultivar. We quantified pollinator effectiveness as a function of the fruit set and fruit weight resulting from single and multiple floral visits (2–15 visits), in comparison with estimates of fruit set and fruit weight resulting from experimental pollination treatments (open‐pollination, cross‐pollination and self‐pollination). Single‐visit effectiveness of fruit set was similar across pollinator taxa but considerably higher in both self‐compatible cultivars. The probability of fruit set in all three blueberry types improved in response to an increasing number of visits, but this relationship was steeper in self‐compatible cultivars: >90% probability of fruit set was achieved in three to five visits. In the self‐incompatible rabbiteye cultivar, 58% fruit set was achieved with 15 visits. Multiple visits improved fruit weight by 27%–48% in self‐compatible cultivars, but there was no relationship in rabbiteye. Pollination deficits in fruit set and fruit weight due to self‐pollination were most pronounced in rabbiteye. Synthesis and applications. Improved understanding of cultivar‐level mating system differences in plants will inform pollination planning and management in agroecosystems. Self‐compatible (highbush) cultivars require less floral visitation to maximize fruit production. Therefore, these cultivars may be best suited to landscapes in which pollinator abundance is low, such as intensive and/or simple landscapes. In contrast, self‐incompatible (rabbiteye) cultivars may benefit from the implementation of mixed‐cultivar crop row plantings to facilitate cross‐pollination.

The European honey bee (Apis mellifera) is managed worldwide for honey production and crop pollination, and is an invasive species in many countries. Wild colonies occupy natural and human‐made cavities and are thought to impact other cavity‐using species. We reviewed documented evidence of wild A mellifera nesting sites globally via a literature review (27 relevant studies) and citizen‐science observations of wild honey bee colonies on iNaturalist (326 observations). Honey bee occupancy rates from published studies were typically low and occupation was often temporary. Citizen‐science data showed that most colonies in cavities had small or narrow entrance holes. Current evidence of perceived competition with honey bees in cavities is largely anecdotal and little is known about the long‐term impacts on survival and reproductive success of other cavity‐occupying species. To guide conservation policy and practice, more empirical research is needed to understand the ecological outcomes of competitive interactions in nesting cavities.

Bees provide pollination services to managed and wild ecosystems but are threatened globally due to multiple stressors, including exposure to contaminants. Perfluorooctane sulfonate (PFOS) is a widely detected and persistent contaminant that accumulates and biomagnifies in food chains. In this exposure effect study, small whole colonies of Apis mellifera (1000 bees) were exposed to PFOS using a purpose‐built cage system over a 4‐week period. The PFOS exposure concentrations were provided to bees in sugar syrup at concentrations detected in the environment, ranging from 0 to 1.6 mg L−1. A range of biological and behavioral responses were monitored. Bee tissue, honey, and fecal matter were analyzed using isotope dilution combined with liquid chromatography–tandem mass spectrometry adapted for bee and honey matrix analysis. Bee mortality increased significantly with PFOS exposure at 0.8 mg L−1 or greater, and brood development ceased entirely at 0.02 mg L−1 or greater. Colony activity, temperament, hive maintenance, and defense were adversely affected in all PFOS exposure treatments compared with the control, even at the lowest PFOS exposure of 0.02 mg L−1. Perfluorooctane sulfonate was detected in bee tissue with a mean bioaccumulation factor of 0.3, and it was also identified in honey and in feces collected from the hive cages. These findings provide the first evidence that PFOS exposure adversely affects honey bee colonies and may transfer to honey. With PFOS contaminating thousands of sites worldwide, our study has implications for exposed bee populations under natural conditions, pollination services, the honey industry, and human health. Integr Environ Assess Manag 2021;17:673–683. © 2021 SETAC

Bees are in decline globally as a result of multiple stressors including pests, pathogens and contaminants. The management of bees in enclosures can identify causes of decline under standardized conditions but the logistics of conducting effect studies in typical systems used across several colonies is complex and costly. This study details a practicable, new and economical cage system that effectively houses live honey bee colonies to investigate the impact of physical conditions, biological factors and environmental contaminants on honey bee health. The method has broad application for a range of effect studies concerning honey bee development, physiology, survival and population dynamics because it enables entire colonies, as opposed to individual workers, to be managed well in captivity.