Forage quality and quantity affect red mason bees and honeybees differently in flowers of strawberry varieties

Abstract

Nectar is a vital source of energy for bees and other pollinators and pollen represents the only source of protein in the diet of bees. Nectar and pollen quality and quantity can therefore affect foraging choices. Strawberry, Fragaria × ananassa (Rosaceae), is a flowering crop that requires insect pollination for the berries to develop optimally. The solitary red mason bee, Osmia bicornis L. (Hymenoptera: Megachilidae), occurs naturally but like the eusocial western honeybee, Apis mellifera mellifera L. (Hymenoptera: Apidae), it is also a commercially reared pollinator used in strawberry production. We hypothesized that strawberry nectar and pollen quality would affect the foraging choice of these two types of bees. In this study nectar and pollen quality is represented by various levels of sugar and protein content, respectively, as well as the number of open strawberry flowers in the experimental field, would affect the foraging choice of these two types of bees. Consistent with previous studies, we found significant and major differences between strawberry varieties in proportions of sucrose in the nectar sugar and in pollen viability – a proxy for pollen protein content. All measured parameters had a significant effect on red mason bee visitation frequency. Contrary to expectations, honeybee foraging behavior was only affected by the number of open flowers and not by any of the quality parameters measured. Our findings indicate that red mason bees were capable of assessing nectar and pollen quality and prioritize accordingly. The pattern observed indicates that individual red mason bees changed foraging focus between strawberry varieties depending on whether nectar or pollen was collected. Our results suggest that targeted breeding of varieties toward high levels of nectar sugar and sucrose concentrations and high pollen protein content may increase pollination success from red mason bees and possibly other solitary bees.

What makes a good pollinator? Abundant and specialised insects with long flight periods transport the most strawberry pollen

“…Although strawberry flowers were highly abundant throughout our sampling period, most pollinator individuals visited wild plants as well as strawberry. This suggests that strawberries alone cannot meet pollinators' nutritional needs, which is consistent with the low sucrose and protein content in the nectar and pollen of Elsanta strawberries (Ahrenfeldt et al, 2019). A potential dependency on wild supplemental resources is also consistent with several studies…”

Pollinator nutrition and its role in merging the dual objectives of pollinator health and optimal crop production

“…To enhance crop pollinator health, it is important to understand the nutritional needs of crop pollinators in tandem with the type and quality of foods accessed. Crop floral resources show phenotypic variations in their nutritional content, at both the inter- and intra-species levels [ 41 ]. At the plant level, spatial and temporal patterns may occur in floral resource quantity and quality.…”

“…Reducing crop pollinator dependency may improve crop production by increasing yields independently of pollinator abundance, which may also translate into reduced competition between managed taxa and wild pollinators [ 118 ]. Different crop cultivars can vary in nectar and pollen quality [ 41 ] and crop domestication can alter floral chemistry with potentially negative impacts on pollinator health [ 119 ]. Breeding crop plants that have high pollinator attractiveness and offer more nutritious rewards may also alleviate some of the pressures faced by pollinators in agricultural landscapes.…”

Biology, Genetic Diversity, and Conservation of Wild Bees in Tree Fruit Orchards

“…They emerge in the spring and early summer when the weather is about 10-15 • C. Mason bees are generalist feeders and forage on a wide variety of flowering plants. Their short flight range and preference for nectar and pollen from fruit trees make them efficient and capable orchard pollinators, because they tend to stay within orchard blocks [35][36][37]. They are low maintenance to keep, requiring only a nesting box to be provided in the springtime and then placed in an insectary under ambient temperature over the winter [32,[34][35][36].…”