Evaluation of the importance of ornamental plants for pollinators in urban and suburban areas in Stuttgart, Germany

Abstract

Urban landscapes are often characterized by a wide range of diverse flowering plants consisting of native and exotic plants. These flower-rich habitats have proven to be particularly valuable for urban pollinating insects. However, the ability of ornamental plants in supporting urban pollinator communities is still not well documented. For this study, we established flower beds at 13 different urban testing sites, which were planted with identical sets of ornamental garden plants. The pollinator visitation patterns were then observed throughout the summer seasons. Over a two-year period, a total of 10,565 pollinators were recorded with wild bees (> 50%, excluding bumblebees) being the most abundant pollinator group. Our results revealed that (I) the assortment of ornamental plants was visited by a high number of urban pollinators for collecting pollen and nectar, and (II) the pollinator abundance and composition varied significantly within the tested ornamental plants. These differences occurred not only among plant species but to the same extent among cultivars, whereby the number of pollinators was positively correlated with number of flowering units per plant. By using a generalized linear mixed model (GLMM) and redundancy analysis (RDA) we identified further significant impacts of the two variables year and location on the insect pollinator abundance and richness. Despite of the local and yearly variations, our approach provided a good and field-applicable method to evaluate the pollinator friendliness in ornamental plants. Such tools are urgently required to validate labels like ‘bee friendly’ or ‘pollinator friendly’ used by plant breeding companies.

Comparison of floral traits in Calibrachoa cultivars and assessment of their impacts on attractiveness to flower-visiting insects

“…Thus, the three most attractive cultivars, 'Neo Firestorm', 'Uno Blue' and 'Neo Blue', might be recommended for urban plantings. As the remaining cultivars have proven to be a less suitable foraging resource for B. terrestris, we suggest using these cultivars in combination with other bumble beefriendly plants, e.g., Dahlia x hortensis, Lavandula angustifolia, Nepeta racemose, Stachys officinalis and Scabiosa columbaria (Rollings and Goulson 2019;Marquardt et al 2020).…”

How wild bees find a way in European cities: Pollen metabarcoding unravels multiple feeding strategies and their effects on distribution patterns in four wild bee species

“…So far, diet preferences have mostly been assessed indirectly through observations of adult bee plant visitation (e.g. Marquardt et al., 2021) or through the morphological identification of pollen grains (Haider et al., 2013; Sedivy et al., 2011). Nonetheless, specific sampling methodologies, such as trap‐nests that allow standardized sampling (Staab et al., 2018), combined with metabarcoding techniques promise to be a powerful tool to characterize and study larval bee diets (Bell et al., 2016; Keller et al., 2015).…”

Rethinking the Connections between Ecosystem Services, Pollinators, Pollution, and Health: Focus on Air Pollution and Its Impacts

“…Generally, it was evidenced how linkages between pollinators, plants, and ecological interactions lead to positive effects on ecosystem services, particularly the regulating and supporting ones. Pollinators, with several wild species, perform an ecosystem service of pivotal value considering the number of pollinators is positively correlated with number of flowers per plant [ 107 ]. A need to gather information on the threats of honeybees and other pollinators is here evident in the light of the worrying news deriving from the growing phenomenon of the decline of pollinators.…”

“…The promotion of conservation, maintenance, and sustainable use of pollinators represents a key challenge. Furthermore, on the basis of very recent studies, it emerges the need to investigate in the future the factors of impact on the abundance and wealth of pollinators and the regulation mechanisms expressed in terms of variance that are not currently known [ 107 ].…”