Urban green roofs as habitat and foraging sites for ants

Abstract Urbanization has caused significant habitat loss for insects and other taxa, prompting interest in engineered green spaces, like green roofs (roofs with plants on them). Green roofs may provide habitat for insects, but there is debate as to how they compare to surrounding ground urban habitat (green strips along sidewalks, street medians, planters, and lawns) and how green roof building height, size, and age affects the biodiversity or nutritional preferences of insects that use these habitats. We sampled ant communities on nine green roofs and their adjacent ground-level habitats in three cities in southwestern and central Ohio, USA to understand how green roofs function as habitat, and tested the ants' nutrient preference (salt or sugar). We found no effect of building height, size, or green roof age on ant abundance or genus richness. While green roofs did have lower abundances and lower genus richness in comparison to ground-level sites, NMDS revealed that roof and ground communities are largely overlapping. Additionally, green roof and ground-level ant communities both preferred sucrose over salt. These results indicate that green roofs are able to support similar ant communities as ground-level urban habitats. Ground and roof ant colonies could be connected, with green roofs acting as foraging sites for ant workers. Together, these results indicate that green roofs support ant communities similar to those at ground level, and that roof and ground populations may be connected through worker foraging across building heights. Our findings highlight the potential of urban green roofs to serve as foraging habitat for ants and contribute to a broader understanding of how insect communities are structured and interconnected across heterogeneous urban landscapes.