The buzz around flower shapes: how Asteraceae corolla dimensions influence pollinator interest in urban green areas

Adequate understanding of plant-pollinator dynamics should be included in any planning of urban green areas so that pollinator biodiversity is supported. Among the factors contributing to plant-pollinator dynamics, this preliminary study specifically examined the impact of corolla tube dimensions on the frequency of insect visitations for foraging. This was accomplished by measuring the corolla dimensions of different Asteraceae species within Ridley Park, UK, and conducting 36 days of non-consecutive observational surveys. Insect identity and visitation frequency to forage on the focal Asteraceae species were recorded. Insect visitors were categorised into three broad taxonomic groups according to comparative proboscis lengths: bumblebees (longer), flies (shorter), and other insects (various; control). The results revealed that Diptera (flies) accounted for the majority of visits, with significant associations found between fly visitation rates and shorter corolla tube lengths/widths. For bumblebees, although trends suggested a potential association between increased visitation rates and larger corolla sizes, no statistically significant relationships were observed for either ray or disk corolla tube lengths. The findings indicate that corolla morphology may play a role in shaping insect foraging in urban green areas. By increasing plant diversity, particularly by incorporating species with a range of corolla dimensions, it may be possible to support a broader spectrum of pollinators. These insights can assist urban park authorities in selecting plant species that promote pollinator biodiversity, contributing to healthier and more resilient urban ecosystems.