Macroinvertebrate diversity and conservation status of Mediterranean ponds in Italy: water permanence and mesohabitat influence

Abstract

1. In Italy small water bodies, especially temporary ones, have been little studied. As a consequence, their conservation value as a biodiversity resource is often overlooked despite Mediterranean temporary waters being listed as a priority habitat in the Habitats Directive (92/43/ EEC). 2. A monitoring programme was designed to determine which factors influence pond species richness, and to analyse the variation in macroinvertebrate community structure within and among ponds. Three main contrasting mesohabitats (macrophyte beds, littoral sediments and central sediments) were defined within 21 ponds (8 permanent and 13 temporary) along the Tyrrhenian coast of Italy near Rome, from which invertebrate macrofauna was collected in March, May and June 2002. 3. The main environmental factors influencing the number of species in ponds were hydroperiod length, depth, surface area, dissolved oxygen concentration and macrophyte species richness. Temporary ponds contained a smaller number of taxa than permanent ponds, but both types of ponds supported similar numbers of rare and threatened species. The total number of species, and in particular Coleoptera, Odonata, and Hemiptera, was higher in macrophyte beds than in both littoral and central sediments. 4. Multivariate analysis (non-metric multidimensional scaling) showed that the overall variation in assemblage composition was greater between temporary and permanent ponds than among mesohabitats, suggesting that environmental variables, such as hydroperiod, have a stronger effect on macroinvertebrate communities than substratum type. 5. In terms of species of conservation interest, this study suggests that both pond types and all mesohabitats should be considered in order to obtain a correct evaluation of pond conservation value.