Abstract
Pollination is a key ecological process, and invasive alien plant species have been shown to significantly affect plant-pollinator interactions. Yet, the role of the environmental context in modulating such processes is understudied. As urbanisation is a major component of global change, being associated with a range of stressors (e.g. heat, pollution, habitat isolation), we tested whether the attractiveness of a common invasive alien plant (Robinia pseudoacacia, black locust) vs. a common native plant (Cytisus scoparius, common broom) for pollinators changes with increasing urbanisation. We exposed blossoms of both species along an urbanisation gradient and quantified different types of pollinator interaction with the flowers. Both species attracted a broad range of pollinators, with significantly more visits for R. pseudoacacia, but without significant differences in numbers of insects that immediately accessed the flowers. However, compared to native Cytisus, more pollinators only hovered in front of flowers of invasive Robinia without visiting those subsequently. The decision rate to enter flowers of the invasive species decreased with increasing urbanisation. This suggests that while invasive Robinia still attracts many pollinators in urban settings attractiveness may decrease with increasing urban stressors. Results indicated future directions to deconstruct the role of different stressors in modulating plant-pollinator interactions, and they have implications for urban development since Robinia can be still considered as a “pollinator-friendly” tree for certain urban settings.
Highlights
Invasive alien plant species have been reported to be a major driver of change in altering biodiversity patterns[1,2,3]
Studies on pollen and nectar collection found that food resources of invasive plants can be either neglected by native pollinators[27,28] or accepted as new foraging alternatives[29,30]
It has been suggested that the high presence of alien plant species in cities[46,47] negatively affects native pollinators due to problems of accessibility with novel flower types or because of differences in the quality of nectar or pollen[18,35]
Summary
Invasive alien plant species have been reported to be a major driver of change in altering biodiversity patterns[1,2,3]. Previous studies showed that alien plant species can significantly modulate important components within plant-pollinator interactions and networks[20,21,22]. Previous studies revealed a range of mechanisms related, for example, to flower morphology[34], nectar chemistry and pollen quality[35], spatial scale[36], and biological plasticity of pollinating species[9]. Effects of different environmental settings on pollinator interactions have received less attention[37]. This is an important research question as recent studies increasingly evidence the role of stressors related to www.nature.com/scientificreports/
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