Urbanized landscapes are characterized by an abundance of impermeable surfaces, concordant fragmentation of native habitats, and overall decreases in resources available for wildlife. Despite this, a variety of floral resources are maintained in cities (often planted by humans for aesthetic rather than ecological purposes) which may benefit flower-visiting insects such as bees, butterflies, flies and other pollinators. Although floral-feeding insects have the potential to benefit urban agriculture, promote urban conservation, and increase ecological exposure of the urban populace, little is known about their distribution or composition in urbanized landscapes. For this study, we analyzed satellite imagery and used ground sampling to identify the distribution and composition of floral resources and floral-feeding insects in New York City.

Results/Conclusions

From 10 July to 14 August 2008, we sampled over 800 1-m² plots, covering a total of 27 km in all five boroughs of the city. Throughout the city, more than half of the flowering plants visited by ‘would be pollinators’ actually are infertile hybrids (e.g. Hydrangea, Hosta) or were located in manicured garden or park settings where human management precludes successful germination and growth of seedlings. Small areas of flowering plants (<5 m²) and flower-visiting insects were found across a variety of urban land uses, from lawns, forests and meadows of city parks to street-side vegetation in single-family, multi-family, and commercially zoned areas of the city. However, larger floral clusters (as quantified by satellite imagery) were relatively rarer, being present in some florally rich community and private gardens and a few park meadows, conservatories and botanical gardens. Across all land uses, the most abundant floral visitors (n = 1363) were Hymenoptera (78% of all observations) and specifically, bees (71% of all observations). Small bees in the genera Lasioglossum, Hylaeus and Ceratina were particularly abundant (33% of all observations), followed by the European honey bee, Apis mellifera (10%). Other insect orders were less abundant, including Diptera (14% of all floral visitors), Lepidoptera (5%) and Coleoptera (3%). Composition of pollinators varied according to city habitat type with relatively more Coleoptera and Lepidoptera on flowers in park settings while Diptera were more common on street-side flowers. Although flower-feeding insects were found on most flowers regardless of location in the city, insect composition (and thus conservation value) varied by location and over all floral patch size.