A MULTIMETHOD APPROACH TO THE ZOOGEOGRAPHY OF THE ITALIAN RIVER BASINS, BASED UPON DISTRIBUTIONAL DATA OF FRESH-WATER INVERTEBRATES .1. THEGENUS HYDRAENA KUGELANN SL (COLEOPTERA, HYDRAENIDAE)

This study aims to provide a basis for detecting a zoogeographic regio nalization of Italian river basin networks. Ninty-six ''primary unit'' based upon dimensional, lithological and geomorphological criteria ha ve been considered. Similarity and information analyses, based upon di stributional data of sixty-two species of the genera (or subgenera) Hy draena and Haenydra, have been carried out to group these units into d istricts. The resulting regionalization in nine main districts substan tially 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 Itali an Hydraena s.1. have also been discussed.