Abstract
Urban environments exert selective pressures on the functional composition of plant communities. Green spaces associated with traffic are widespread in cities and could therefore support pollinator biodiversity. This emphasizes the need to characterize the diversity of pollination-related traits within plant communities occupying these habitats. Hence, we investigated how pollination-related functional traits are associated with urban indicators in green spaces exposed to traffic, and how the functional diversity of these traits influences pollinator richness. Data on vascular plant communities and insect pollinators were collected from 90 traffic-exposed locations, including traffic islands, parking lots, and road verges, in three Finnish cities. We recorded information on six pollination-related plant and floral traits for each plant species. These functional traits and their diversity, calculated from presence-absence data, were then explored in relation to three urban indicators: imperviousness, length of roads, and distance to city centers. We observed that species with larger floral units, yellow-colored flowers, and hymenopteran pollination were positively associated with imperviousness and/or length of roads. Furthermore, species were generally shorter and more commonly short-lived (i.e., annuals or biennials) in traffic islands than in road verges. Functional richness (FRic) and functional dispersion (FDis) of traits decreased with increasing imperviousness, suggesting that altered environmental conditions related to high imperviousness might filter plant species with less adaptive trait combinations. Pollinator richness was positively linked to FRic, but decreased with increasing FDis of pollination-related traits. Our results suggest that in traffic-exposed plant communities, species with certain pollination-related traits adapted to urban conditions may be selectively favored.