Environmental heterogeneity and benthic macroinvertebrate guilds in italian lagoons

Abstract

1 - Lagoons are ecotones between freshwater, marine and terrestrial biotopes, characterized by internal ecosystem heterogeneity, due to patchy spatial and temporal distribution of biotic and abiotic components, and inter-ecosystem heterogeneity, due to the various terrestrial-freshwater and freshwater-marine interfaces. 2 - Here, we carried out an analysis of environmental heterogeneity and benthic macro-invertebrate guilds in a sample of 26 Italian lagoons based on literature produced over a 25 year period. 3 - In all, 944 taxonomic units, belonging to 13 phyla, 106 orders and 343 families, were recorded. Most species had a very restricted geographic distribution range. 75% of the macroinvertebrate taxa were observed in less than three of the twenty-six lagoons considered. 4 - Similarity among macroinvertebrate guilds in lagoon ecosystems was remarkably low, ranging from 10.5%±7.5% to 34.2%±14.4% depending on the level of taxonomic resolution. 5 - Taxonomic heterogeneity was due to both differences in species richness and to differences in species composition: width of seaward outlet, lagoon surface area and water salinity were the most important factors affecting species richness, together accounting for up to 75% of observed inter-lagoon heterogeneity, while distance between lagoons was the most significant factor affecting similarity of species composition. 6 - Both environmental filtering and passive diffusion were found to be influential processes in shaping macroinvertebrate guilds in lagoon ecosystems.