Chironomids (Diptera) of temporary and permanent ponds in Central Italy: a neglected invertebrate group in pond ecology and conservation

In spite of their ubiquity and the numerous species present in all freshwater ecosystems, chironomids have generally been considered only at the family, subfamily, or tribe level in ecological studies because of the difficulties of specific or generic identification of larvae. We investigated the chironomid communities in 21 astatic ponds in central Italy with the aim of examining the differences between temporary and permanent ponds and within three contrasting mesohabitats. In March, May, and June 2002 we collected a total of 40 taxa (species, species groups, and genera) of chironomids in 13 temporary and eight permanent ponds located in four protected areas along the central Italian coast near Rome. Chironomid taxa discriminated the two pond types along a wet phase duration gradient, with permanent ponds showing higher taxa richness and densities mainly due to their larger size, lower nutrient contents, higher oxygen concentrations, more transparent water, and greater macrophyte species richness than temporary ponds. Moreover, some taxa showed a clear preference for different mesohabitats (i.e., Corynoneura scutellata, Isocladius sylvestris, and Paratanytarsus spp. for macrophyte beds; Chironomus spp. and Psectrotanypus varius for central sediments; and Smittia sp. for littoral sediments). The results indicate that chironomids apparently offer a good proxy for describing pond characteristics (i.e., wet phase duration, mesohabitat features) as well as the entire macroinvertebrate fauna.