Italian subspecies of the asp viper, Vipera aspis: patterns of variabilityand distribution

The asp viper, Vipera aspis, is distributed in western Europe and comprises several morphological subspecies other than the nominal form, V. a. aspis of northern to southern France: V a. zinnikeri, V. a. atra, V. a. francisci redi, V. a. hugyi. Each form is very often distinguishable, both by dorsal colour pattern and number of ventral scales. Examining a balanced sample fo r each subspecies and each sex from Italy and other areas, we found that th e distributive patterns of Italian populations are as follows: V. a atm is widely distributed throughout northwestern Italy, reaching the Ligurian Sea coasts; it passes westwards into France up to most of the Haute Provence r egion, turning northwards up to the Savoie region. Instead, V. a. francisci redi extends eastwards throughout the Po plain and southwards to southern I taly. The distribution limit of V. a. hugyi extends from northern Apulia so uthwards to the Irpini mountains, and the slopes of Mr. Vesuvius volcano, a nd the remaining part of Italy and Sicily. Most of the known morphological differences between aspis and francisciredi do not seem to be consistent. T he subspecies montecristi is identical to hugyi. Some hypotheses of possibl e causes of different distributive patterns are presented.