Molluschi terrestri delle Alpi sudorientali

BIOGEOGRAPHIA — vol. XI/I - 1987 Biogeografia delle Alpi Sud«OrienraIi Molluschi terrestri ‘delle Alpi sudorientali ALBERTA BOATO, MARCO BODON, M. MANUELA GIOVANNELLI, . PAUL MILDNER Dz'p¢zrz‘imem‘o di Biologia, Um'verrz'tz2 dz' Pzzdova Istzmto di Zoologzkz, Um'ver5z'z‘oi di Siemz Mureo Friulzmo dz’ Storm Ncztzzmle, Udirze Lmzdermureum fiir Kt'z’rm‘en, Klagenfim‘ SUMMARY The research, carried out in the years 1978-1987, concerns the terrestrial Prosobranchia and Pulmo- nata from the southeastern Alps, in which the whole Friuli region, the Isonzo Valley and the Carso Triestino are included. Results are presented as a species list (202 species), where for each taxon are provided: quotations from literature, with synonyms; sampling localities; unpublished records from mu- seum collections, if relevant; range; notes on taxonomic problems and distribution. A critical list of taxa of doubtful presence in the area, or uncertain taxonomic position is also provided. For the biogeographical analysis, the southeastern Alps were divided in three subareas: Carnic Low- land, Prealps and Alps (west of the Fella-Tagliamento riverine systems); Julian Lowland, Prealps and Alps (east of the Fella-Tagliamento line, including the Isonzo Valley); Carso Triestino. The binary (pre- sence-absence) Sorensen similarity index has been evaluated for all possible comparisons between the species lists, of following areas: the southeastern Alps (considered as a whole); the three sub—areas (Carnic Alps, Julian Alps, Carso); the central-western Slovenia; the southern Carinthia; the Istrian peninsula; the Venato. The relative percentage of the chorological components of the above cited areas are also com- pare . As far as their terrestrial malacofauna is concerned, the southeastern Alps probably represent the richest italian region as to species number. As species presence-absence, SE Alps as a whole display their highest similarity with the Veneto, and then with Istria, while Carinthia and Slovenia cluster together. In their chorological composition, SE Alps appear to be rather heterogeneous: in fact, in the Julian Alps and in the Carso Triestino the Dinaric and Balcanic components, more xerotetmophilic, are prevailing; species with this type of distribution reach very often the northern and western edges of their range in corre spondence of Isonzo or Tagliamento rivers. Ln contrast, in the Carnic Alps the E-Alpine-Carpathic com- ponent is strongly represented. Species with this type of distribution are linked to cool habitats and were probably arrived in SE Alps from the mountains of southeastern Europe, being favoured by the oceanic climate and continuity of mountain systems. Moreover, in SE Alps, the fauna is enriched by the presence of several endemic species, which presence is probably related to the refuge center role played by this region during the Pleistocene glacial periods, and by the occurrence of several cave habitats. INTRODUZIONE Come «E state piu volte ribadito da molti, ed in particolare da La Greca (1964, 1975), una ricerca biogeografica non puo dare risultati attendibili se non e fondata su taxa ben definiti e dei quali sia anche esaurientemente conosciuta la distribuzione geografica. Queste condizioni, purtroppo, non si possono dire pienarnente soddisfatte per quanto concerne i molluschi terrestri, sui qualj spesso mancano revisioni svolte secondo moderni criteri tassonomici o cornunque secondo metodologie 429