Pattern of structure and diversity of the macrobenthic assemblage in volcanic lakes of Central Italy.

Despite the large number of diversity studies on lake macroinvertebrates, much of our understanding of biodiversity is based on local (alpha diversity) or regional (gamma diversity) inventories, whereas variation in species diversity at the lake level (beta diversity) remains poorly understood. Beta diversity increases as the similarity in species composition among sites decreases; therefore it is a measure of the extent to which the diversity of two or more spatial units differs. Here we assembled a large dataset on macrozoobenthos (371 samples, 207 taxa) collating data from previous studies from different sites and habitats in 5 lakes belonging to the volcanic district of central Italy. The lakes ranged between 1.8 and 51 km² of surface area and between 31m and 175m of max depth and have a different trophic state. Invertebrate taxa richness composition and similarity in species composition was compared among habitats within a lake and among lakes using univariate and multivariate displays. Additionally, variation in the assemblage structure was related to several environmental variables connected to euthrophication pressure and local habitat degradation.