Title: L’Ittiofauna continentale dell’Appennino umbro-marchigiano, barriera semipermeabile allo scambio di componenti primarie tra gli opposti versanti dell’Italia centrale
Abstract: BIOGEOGRAPHIA — vo/. X V/I — 1993 (Pubb/icato il 31 ottobre 1994) II popolamento animale e vegetale deli'Appennino Umbro—Marchigiano Ifittiofauna continentale dell’Appennino umbro—marchigano, barriera semipermeabile allo scambio di componenti primarie tra gli opposti versanti dell’Italia centrale PIER GIORGIO BIANCO Dz'pzzrtz'mem‘0 dz‘ Zoologzkz, Via Mezzocmmorze, 8, 8013 4 Nczpoli Key words: central Italy, freshwater fishes, biogeography, taxonomy, human interference. SUMMARY The primary and primary-like freshwater fish fauna of central Italy is formed by two distinct regional as- semblages. In basins of the western slope of central Appenninian chain of mountains lives the whole fish com- munity of the tuscano-latium ichthyogeographic district. On the eastern slope only a part of the species living in the Po basin (padano-venetian district). But several elements are shared. The Appenninians played an im- portant role either as a barrer for endernics or as a way of dispersion for shared species. The wider spread pri- mary or primary-like species (sometimes european ones), are cold-water or moderately cold-water adapted ri- verine forms. Most of the species endemic to one of the two districts, belong to the category of warm-water adapted riverine or lacustrine ones. Cold adapted species at able to use river captures to cross high mountains while the warm adapted have less opportunities for dispersal (river confluences or river captures on low lands). The detailed distribution of most of italian species has been altered by human interferences. The natu- ral outline of general distributions of each species has pointed out by the analyses of historical collections. The origins of primary fish fauna is dated not earlier than Messinian (5 MYA) for the tuscano—latium district, and Pleistocene (0.9 MYA) for southern padano—venetian district. The last processes. of natural homogenization inside each district could be dates historical for the tuscano-latium district, and wurrnian about 10—15.000, years ago, for southern padano-venetian one. ' INTRODUZIONE I bacini degli opposti versanti dell’Appennino umbro-marchigiano ospitano dei complessi ittiofaunistici parzialmente diversificati. ll versante tirrenico com- prende gran parte del distretto tosco-laziale (dal Serchio all’Arno), mentre in quello adriatico, si localizza la propaggine meridionale del distretto padano- veneto. Ciascun distretto e caratterizzato da propri endemisrni. I bacini tirrenici ospitano l’insieme complessivo delle componenti tosco-laziali. Quelli adriatici (q‘) Lavoro eseguito nell’ambito del programma «Componenti extrapaleartiche della fauna italiana e me- diterranea» Einanziato con fondi MP1 40% e CNR. 427