A multimethod approach to the zoogeography of the Italian river basins, based upon distributional data of freshwater invertebrates. I. The genushydraenakugelann s.l. (coleoptera, hydraenidae)

This study aims to provide a basis for detecting a zoogeographic regionalization of Italian river basin networks. Ninty‐six ≪primary units≫ based upon dimensional, lithological and geomorphological criteria have been considered. Similarity and information analyses, based upon distributional data of sixty‐two species of the genera (or subgenera) Hydraena and Haenydra, have been carried out to group these units into districts. The resulting regionalization in nine main districts substantially agrees to some extent with earlier analyses based on classical historical biogeography. As a parallel development of the method, the patterns of biodiversity and some aspects of the zoogeography of Italian Hydraena s.l. have also been discussed.