A screening-level assessment of the pollinator-attractiveness of ornamental nursery stock using a honey bee foraging assay

Abstract

In urban and suburban landscapes characterized by extensive designed greenspaces, the support of pollinator communities hinges significantly on floral resources provided by ornamental plants. The attractiveness of ornamental plants to pollinators, however, cannot be presumed, and some studies suggest that a majority of ornamental plant varieties receive little or no pollinator visitation. Here, we harness the sampling power of the western honey bee, a generalist pollinator whose diet breadth overlaps substantially with that of other pollinators, to survey the utilization of ornamental plants grown at three commercial nurseries in Connecticut, USA. Using a combination of DNA metabarcoding and microscopy, we identify, to genus-level, pollen samples from honey bee colonies placed within each nursery, and we compare our results with nursery plant inventories to identify the subset of cultivated genera that were visited during pollen foraging. Samples were collected weekly from May to September, encompassing the majority of the growing season. Our findings show that some plant genera known to be cultivated as ornamentals in our system, particularly ornamental trees and shrubs (e.g. Hydrangea, Rosa, Spiraea, Syringa, Viburnum), functioned as major pollen sources, but the majority of plants inventoried at our nurseries provided little or no pollen to honey bees. These results are in agreement with a growing body of literature highlighting the special importance of woody plants as resources for flower-visiting insects. We encourage further exploration of the genera highlighted in our data as potential components of pollinator-friendly ornamental greenspace.

Wild bee functional diversity and plant associations in native and conventional plant nurseries

“…More research on the attractiveness of native and non-native ornamental plants (e.g. Sponsler et al, 2020) to specialist and generalist species in nurseries may shed light on such patterns.…”

Shifts in honeybee foraging reveal historical changes in floral resources

“…The plants detected using DNA metabarcoding and melissopalynology have been compared in previous studies with concordance found between the two methods 45 – 48 . Both methods detect the same major taxa, but rarer species in a sample are less likely to be found consistently, both when comparing methods and also during replicates of the same method 45 – 47 .…”

Pollinators and plant nurseries: how irrigation and pesticide treatment of native ornamental plants impact solitary bees

“…Ornamental plant nurseries represent a major agricultural sector that remains relatively unexplored with regard to its support of local insect communities. While ornamental plants and the urban greenspaces they occupy are well known to serve as foraging resources for pollinators [1,2], the role of horticultural nurseries as bee foraging habitat has just recently received attention [3][4][5][6]. While these facilities occupy less land area than conventional row crops do [7], their high floral diversity [3][4][5] and the potential for exposure to elevated concentrations of insecticides in floral resources [8][9][10] render nurseries pertinent to study from the perspective of wild bee ecology.…”

“…While ornamental plants and the urban greenspaces they occupy are well known to serve as foraging resources for pollinators [1,2], the role of horticultural nurseries as bee foraging habitat has just recently received attention [3][4][5][6]. While these facilities occupy less land area than conventional row crops do [7], their high floral diversity [3][4][5] and the potential for exposure to elevated concentrations of insecticides in floral resources [8][9][10] render nurseries pertinent to study from the perspective of wild bee ecology. However, we lack quantitative knowledge on how local management practices in horticulture may interact to affect resident wild bees, particularly solitary species.…”

“…While ornamental plants and the urban greenspaces they occupy are well known to serve as foraging resources for pollinators [1,2], the role of horticultural nurseries as bee foraging habitat has just recently received attention [3][4][5][6]. While these facilities occupy less land area than conventional row crops do [7], their high floral diversity [3][4][5] and the potential for exposure to elevated concentrations of insecti-and application methods. Multiple factors influence the amount of these systemic insecticides entering pollen and nectar of ornamental plants [15,16], but we have a poor understanding of these factors and how they interact [17].…”