Water availability and proximity to natural areas influence plant and terrestrial invertebrate communities in urban stormwater basins and ponds

A variety of stormwater infrastructure such as constructed wetlands, rain gardens, vegetated drainage channels and retention ponds are primarily used for managing water runoff, but these environments can also foster biodiversity. Despite extensive literature about certain taxa (e.g., amphibians, aquatic macroinvertebrates, etc.) found in these human-made environments, the terrestrial plants and invertebrates present there remain understudied. Here, we compared alpha and beta diversity of plant and terrestrial invertebrate communities and assessed the influence of landscape characteristics on their composition in different types of urban stormwater basins and ponds. Plants and terrestrial invertebrates were identified in the main body (excluding the aquatic section) and on the banks of 54 basins and ponds (dry basins, wet basins with and without a water channel and retention ponds) in Quebec City and Trois-Rivières, in Eastern Canada. Results showed poor and homogenous plant and invertebrate communities in dry basins. Wet basins had the highest plant alpha diversity, with more facultative wetland species than the two other types. Wet basins with and without a water channel had similar plant and invertebrate composition, and wet basins and retention ponds were the most heterogeneous. Retention ponds (with permanent water) had distinct communities with fewer plant species than wet basins. The presence of natural areas around the infrastructure significantly influenced communities within a 2000 m and 500 m radius for plant and invertebrate communities, respectively. Wetland plant species were generally found in infrastructure close to natural areas, whereas tolerant and opportunist species were associated with disturbed environments. Our results suggest that enhancing diversity of the stormwater basins and ponds at the regional and local (microhabitat) scales has the potential to maximize diversity of plants and terrestrial invertebrates.