Mountain protected areas as refuges for threatened freshwater species: the detrimental effect of the direct introduction of alien species

One of the main threats to native European crayfish species is presented by the spread of invasive ones, which are vectors of the crayfish plague Aphanomyces astaci. In particular, the Austropotamobius pallipes complex is suffering extensive decline in its whole distribution range. In this paper, we describe a case of extinction of a native population of the A. pallipes complex driven by the direct human introduction of the alien species Orconectes limosus, in a mountain protected area in northern Italy. The local extinction event of the native crayfish population is reported, and the factors that drove it are reconstructed. Our results help to better understand the threats to native crayfish species occurring even in protected areas, as well as to establish proper prevention and management actions.