Taxonomic Reassessment of Freshwater Mussels from the Western Balkans Reveals an Overlooked but Critical Refugium and Defines Conservation Priorities

Freshwater mussels are an endangered group of animals, especially in the water bodies of Central and Western Europe. Conservation priorities were established for many endangered freshwater mussel species in the last decade. Here, we present new data on a cryptic refugium of freshwater mussels in the Western Balkans. Two species, Anodonta exulcerata Porro, 1838 and Unio elongatulus Pfeiffer, 1825, were discovered in Montenegro for the first time. The phylogenetic position and taxonomic status of freshwater mussel species from Montenegro were studied by means of an integrative approach, combining morphological data and COI gene sequences. Unio carneus Küster, 1854 stat. rev. represents a species with a restricted range, which is endemic to the Western Balkans. A viable population of Microcondylaea bonellii (Férussac, 1827) was discovered in the Zeta River. This species was not mentioned in Montenegro since the 1900s. A significant level of genetic diversity was revealed for the studied species. In the Skadar Lake basin, freshwater mussels from diverse ecological groups were discovered. Rheophilic species of freshwater mussels may represent ancient lineages, which need special conservation planning. Conservation priorities should be aimed at the protection of freshwater mussel habitats on the Balkan Peninsula

Taxonomic Reassessment of Freshwater Mussels from the Western Balkans Reveals an Overlooked but Critical Refugium and Defines Conservation Priorities

Freshwater mussels are an endangered group of animals, especially in the water bodies of Central and Western Europe. Conservation priorities were established for many endangered freshwater mussel species in the last decade. Here, we present new data on a cryptic refugium of freshwater mussels in the Western Balkans. Two species, Anodonta exulcerata Porro, 1838 and Unio elongatulus Pfeiffer, 1825, were discovered in Montenegro for the first time. The phylogenetic position and taxonomic status of freshwater mussel species from Montenegro were studied by means of an integrative approach, combining morphological data and COI gene sequences. Unio carneus Küster, 1854 stat. rev. represents a species with a restricted range, which is endemic to the Western Balkans. A viable population of Microcondylaea bonellii (Férussac, 1827) was discovered in the Zeta River. This species was not mentioned in Montenegro since the 1900s. A significant level of genetic diversity was revealed for the studied species. In the Skadar Lake basin, freshwater mussels from diverse ecological groups were discovered. Rheophilic species of freshwater mussels may represent ancient lineages, which need special conservation planning. Conservation priorities should be aimed at the protection of freshwater mussel habitats on the Balkan Peninsula

Postglacial Expansion Routes and Mitochondrial Genetic Diversification of the Freshwater Pearl Mussel in Europe and North America

The freshwater pearl mussel Margaritifera margaritifera is a unionid species distributed across Northwestern Russia, Fennoscandia, Western and Southwestern Europe, and the Atlantic Coast of North America. In this study, we reconstructed the post-glacial expansion routes of this species based on FST genetic distances and the fact that M. margaritifera distribution is directly connected with salmonid expansion. The freshwater-pearl-mussel populations from North America and Northeastern Europe were the closest groups, judging by FST distances, supporting the concept of the North Atlantic Salmo salar colonization of the Barents and White Sea basins. We also documented that unique haplotypes in the populations of the Baltic and White Sea basins may have originated in isolated glacial refugia in Eastern and Northeastern Europe. The Iberian clade was the most distant group of populations, which is consistent with the previously observed role of the Iberian Peninsula as a glacial refugium. The high genetic diversity in the populations of Northern and Eastern Karelia was facilitated by migrants utilizing complex periglacial hydrological networks and by admixture in the contact zone where the migration flows met. We confirm that this region should be considered as a major center of genetic diversity within the European part of the species’ range

Postglacial Expansion Routes and Mitochondrial Genetic Diversification of the Freshwater Pearl Mussel in Europe and North America

The freshwater pearl mussel Margaritifera margaritifera is a unionid species distributed across Northwestern Russia, Fennoscandia, Western and Southwestern Europe, and the Atlantic Coast of North America. In this study, we reconstructed the post-glacial expansion routes of this species based on FST genetic distances and the fact that M. margaritifera distribution is directly connected with salmonid expansion. The freshwater-pearl-mussel populations from North America and Northeastern Europe were the closest groups, judging by FST distances, supporting the concept of the North Atlantic Salmo salar colonization of the Barents and White Sea basins. We also documented that unique haplotypes in the populations of the Baltic and White Sea basins may have originated in isolated glacial refugia in Eastern and Northeastern Europe. The Iberian clade was the most distant group of populations, which is consistent with the previously observed role of the Iberian Peninsula as a glacial refugium. The high genetic diversity in the populations of Northern and Eastern Karelia was facilitated by migrants utilizing complex periglacial hydrological networks and by admixture in the contact zone where the migration flows met. We confirm that this region should be considered as a major center of genetic diversity within the European part of the species’ range