Modelling environmental niche for the endangered freshwater crayfish species Austopotamobius pallipes complex in Northern and Central Italy

The potential distribution of endangered species is a necessary step to assess species conservation status and manage reintroduction plans. In the context of the Life project CRAINat (LIFE+ 08 NAT/IT/000352) on the endangered Austropotamobius pallipes complex, we modelled the environmental niche of the species in two large areas of Northern (Lombardy, 43 records) and Central Italy (Abruzzo, Province of Isernia, Gran Sasso e Monti della Laga National Park; 69 records). Suitability models were built by using the maximum entropy approach as implemented in the MaxEnt software (vers. 3.3), which predict the occurrence of a species using presence-only data. The occurrence of A. pallipes was modelled using six variables: altitude, slope, aspect, anthropic disturbance (3 classes derived from Corine Land Cover), mean temperature of warmest quarter (from www.worldclim.org) and distance from stream system (as control variable accounting for small streams not solved in the digital map of rivers within studied areas). Each study area was modelled independently. Both potential distribution obtained high performance scores as measured by the AUC index (N-Italy: 0.92; C-Italy: 0.88). In both areas, altitude, slope and distance achieved the greatest predictive power. Moreover, in C-Italy the mean temperature of warmest quarter was also signifi cant in predicting species occurrence. The white-clawed crayfi sh prefer habitat next to stream system and with low slope; in N-Italy the species select the altitude interval of 400-600 m, while in the C-Italy it occur preferentially within 800-1200 m, due to the increase of temperature.