Urbanisation and invasion as drivers of insect diversity

Abstract

Urbanisation often reduces local biodiversity, yet cities can maintain high total species richness, a pattern underlying the "cities-as-bioarks" hypothesis that urban remnant habitats serve as refuges for native species. We surveyed ants across 60 sites in Atlanta, Georgia (USA), spanning streetscapes, manicured parks, and forested parks. Contrary to bioark predictions, native richness was lowest in forested parks and declined strongly with abundance of the invasive Asian needle ant, Brachyponera chinensis, indicating that habitat protection alone is insufficient without active invasive species management. Because sampling protocols developed for natural habitats may not capture urban ant diversity effectively, we also evaluated four common methods (pitfall trapping, leaf-litter extraction, hand collection, and baiting) at these sites and reviewed 86 urban ant studies published between 2001 and 2025. Hand collection and pitfall trapping captured the greatest diversity, yet pitfall traps and baiting dominate the literature while hand sampling remains underused.