Nestedness-patterns of Odonata assemblages in artificial and natural aquatic habitats reveal the potential role of drinking troughs for aquatic insect conservation

Nestedness patterns including both artificial and natural habitat may represent evidence of such habitats’ importance in community assembly and conservation of animals inhabiting those sites. Odonata often colonize drinking troughs (artificial water reservoirs) and thus they are good study models as umbrella species. We investigated if a network of artificial (troughs) and natural (pools) aquatic habitats could create a nested subset pattern for Odonata assemblages. We surveyed all the troughs present in the Castelporziano Estate (Italy, Lazio). Odonata larvae have been collected and identified. Data of a previous paper on 18 natural pools and ponds, and our samplings of 16 troughs were organized into a presence-absence matrix. The Odonata assemblage within natural and artificial habitats is significantly nested with both NODF and T metrics. Odonata species found in the troughs represented 40% of the total species pool. Some troughs interspersed with the natural pools in the nested order: eight troughs were richer in species than some natural pools, despite the big difference in surface area. Pristine water bodies and their area may not represent major constraints for species to oviposit and for larvae to grow. Drinking troughs can be highly relevant for representing refuges in the absence or decline of natural ponds and pools: lacking in top-predators (fishes), they are small “island” habitats that support the generations of Odonata (or other aquatic macroinvertebrates) during dry periods of natural water bodies. The use and focused management of such habitats can be an effective practice for freshwater ecosystems management and Odonata conservation.