Success of an exotic snail Physella acuta in anthropogenically impacted Patagonian streams

The expansion of exotic species is one of the greatest threats to biodiversity and is a significant component of global change that occurs at increasing rates due to the removal of natural barriers and the global transport of species. The snail Physella acuta, has expanded into numerous aquatic environments worldwide, given a set of traits that allows the species to thrive in new and harsh environments. This study documents changes in the composition and structure of the malacofauna and examines the presence of established and expanding populations of P. acuta in the Esquel-Percy basin (Patagonia, Argentina), which has been altered by wastewater treatment plants discharges (WWTPs). The population density of P. acuta in the studied area increased from less than 15 ind/m2 in 2005 to 1800 ind/m2 in 2016-2017. This species was the dominant mollusk at the two post-urban sites, under poor environmental conditions. Understanding the introduction pathways of exotic species to prevent and control their establishment and spread is essential since biological invasions constitute a major threat to freshwater ecosystems.