Heterogenic aquatic vegetation promotes abundance and species richness of Odonata (Insecta) in constructed agricultural wetlands

Natural wetlands are among the most threatened habitat types worldwide. They contain a high diversity of macroinvertebrates, including dragonflies and damselflies (Insecta: Odonata). In agricultural landscapes, new wetlands have been constructed to filter nutrients and solid matter from agricultural runoff. These types of wetlands may also benefit Odonata as new breeding habitats. However, it is not yet clear what environmental characteristics of constructed wetlands are important for Odonata. We studied 20 constructed agricultural wetlands in Central Finland and asked whether Odonata are able to use these wetlands as breeding habitats, and which environmental characteristics (aquatic vegetation, water area, shoreline length, bottom type diversity, water transparency, and pH) of the wetlands affect odonate abundance and species richness. The constructed wetlands hosted altogether 17 odonate species. Odonate abundance was positively associated with the number of aquatic vegetation growth forms of the wetland. Odonate species richness was associated positively with abundance, floating-leaved vegetation, and water transparency. Constructed agricultural wetlands support local diversity of common odonate species. Although protecting the remaining natural wetlands is of primary importance, constructed wetlands can add suitable wetland habitats in the agricultural landscape. From the perspective of Odonata, heterogenic aquatic vegetation and water quality are features worth promoting when constructing and managing agricultural wetlands.