Freshwater mussel conservation in southern South America: update on distribution range and current threats

Globally, the Unionida have suffered an increasing decline in both their populations and distribution range. This phenomenon has been well documented in Europe and North America. In Argentina, the study of the group reached its height between 1960 and 1980, producing valuable but now outdated information. This study aims to explore the distribution range before and after 1990 and discuss the potential threats to Unionida (Hyriidae and Mycetopodidae families) in Argentina. We analyzed bibliographies, databases, and new samplings following the malacological provinces of Argentina (MP) zoogeographic scheme. A total of 2452 georeference records were analyzed. Of the 35 species detected up to 1990, 17 (48%) have not been recorded since that year. Freshwater mussels are recorded in seven of the eight MP and in six there has been a reduction of more than 50%. Climate change (increasing water temperature, droughts or extreme floods, and fires), globalization (invasive species), and human activity (intensive agriculture, wastewater discharge, construction of dams or river channelization, and commercial exploitation) have all contributed to the decline and reduction of native mussel populations, leading to range reduction and extirpation. The results of the present study will allow future research to estimate the endangered status and degree of conservation of unionidan species in southern South America, which provide multiple ecosystem services.