Dragonfly taxonomic and functional responses to urbanized streams in southeastern Europe, with management recommendations

As cities rapidly expand worldwide, urbanization is one of the main drivers of natural habitat and biodiversity loss. Even though urban freshwater habitats are important in biodiversity conservation, the ecological requirements of aquatic insects, such as dragonflies (Odonata), are insufficiently known.

We studied dragonfly assemblages based on nymph records in nine urban streams in a capital city in south‐eastern Europe. The upper sections of all streams were in a natural state, while lower sections were urbanized.

Dragonfly taxonomic and functional assemblage metrics were similar between natural and urbanized stream sections. However, there was downstream species turnover, where habitat specialists were replaced by generalists, also reflected in significant differences in some traits in the two types of stream sections. These results suggest that human disturbance did not significantly reduce overall trait space but rather altered the composition of traits within assemblages.

Overall, natural stream sections had a significantly higher conservation value than urbanized ones.

Dragonfly assemblages were strongly shaped by natural and anthropogenic environmental drivers such as elevation, habitat shade, percentage of microhabitats with fine sediments, physical and chemical water properties and level of anthropogenic impact, especially substrate modification.

Urbanized sites with higher habitat heterogeneity (higher variety of microhabitats, including macrophyte vegetation) had more diverse dragonfly assemblages, whereas sites with artificial substrates (e.g., concrete) were unsuitable for many species.

The results emphasize the importance of including natural habitat heterogeneity in urbanized areas for conservation of dragonfly stream assemblages, which is our main management recommendation.