Integrative taxonomy, biogeography and conservation of freshwater mussels (Unionidae) in Russia

Freshwater mussels are ecosystem engineers and keystone species in aquatic environments. Unfortunately, due to dramatic declines this fauna is among the most threatened globally. Here, we clarify the taxonomy and biogeography of Russian Unionidae species based on the most comprehensive multi-locus dataset sampled to date. We revise the distribution and assess the conservation status for each species. This fauna comprises 16 native species from 11 genera and 4 tribes: Anodonta, Pseudanodonta (Anodontini); Amuranodonta, Beringiana, Buldowskia, Cristaria, Sinanodonta (Cristariini); Middendorffinaia, Nodularia, Unio (Unionini); and Lanceolaria (Lanceolariini). No country-level endemic species are known in Russia, except for Buldowskia suifunica that may also occur in China. Sinanodonta woodiana, a non-native species, was introduced from China. Russia comprises the northern parts of Western and Eastern Palearctic subregions. The first subregion with six species encompasses a huge area from the western boundary of Russia to the Lena Basin in Siberia. The second subregion with 10 species covers the Amur Basin, rivers east of the Lena Basin, coastal basins of the Japan Sea, and the North Pacific Islands. The fauna of Russia primarily includes widespread generalist species that are here considered Least Concern (LC). However, Buldowskia suifunica and Sinanodonta lauta have restricted distributions and are assessed here as Vulnerable (VU) and Endangered (EN), respectively.


Tribe Cristariini Lopes-Lima et al., 2017
Genus Beringiana beringiana (Middendorff, 1851) =Anodonta cellensis var. beringiana Middendorff (1851) Comments: This variable and widespread species has been described under various names, the oldest available of which is Beringiana beringiana. The majority of younger available names were once applied to morphological varieties with minute differences in the shell shape and convexity that were thought to be endemics of certain lakes, streams, and rivers 12,[19][20][21][22][23][24][25] . We place these names to the synonymy of Beringiana beringiana based on conchological similarity, multi-locus molecular data, and geographic evidence. In contrast, Beringiana georgiensis Bogatov & Starobogatov, 2001  Buldowskia suifunica (Lindholm, 1925) =Anodonta arcaeformis var. suifunica Lindholm (1925) Cristaria plicata (Leach, 1814) =Dipsas plicatus Leach (1814) Comments: Here, we follow the commonly accepted concept of this species 6,35,36 . The correct list of synonyms is presented by Klishko et al. 35,36 . Sinanodonta lauta (Martens, 1877) =Anodonta lauta Martens (1877) Comments: This interesting species has a broad range, but in Russia its native populations are known from a few coastal freshwater basins close to the boundary of North Korea. Bespalaya et al. 42 and Kondakov et al. 43 mentioned this species as Sinanodonta ovata based on the results of molecular analyses of the topotypes of this nominal taxon from the Gladkaya River. Kondakov et al. 43 assumed that this species may have an older available name among the Japanese nominal taxa. Sinanodonta lauta seems to be the oldest name for this species. Two nominal taxa described from the Gladkaya River are considered synonyms of Sinanodonta lauta.

Genus
Sinanodonta schrenkii (Lea, 1870) =Anodonta magnifica Schrenck (1867) Comments: One Sinanodonta species inhabits the Amur and Razdolnaya basins. Sayenko et al. 46 applied the name Sinanodonta amurensis  to this species. However, Kondakov et al. 43 showed that Sinanodonta schrenkii (Lea, 1870) is the valid oldest name for this taxon. Fisher 47 listed Lea's name for this species in his "Catalogue et distribution geographique des mollusques terrestres, fluviatiles & marins". The rest of nominal taxa of Sinanodonta described from the Amur and Razdolnaya basins are considered synonyms of this species based on conchological similarity, multi-locus molecular data, and geographic evidence.
National conservation status: Non-native species, Not Applicable (NA).
Distribution: A non-native population of this species has been discovered in the Yenisei River, Eastern Siberia 42 . Native to the Yangtze River basin in China but widely introduced in Europe, Central Asia, and Myanmar 42,43,[49][50][51] .
Comments: Sinanodonta woodiana in its current understanding represents a complex of 6-7 cryptic species 33,49,52 . The taxonomic position of the temperate invasive lineage is unclear. While Kondakov et al. 43 assumed that Sinanodonta gibba can be its oldest available name, Dr. Arthur Bogan (pers. comm., 2019) recommend to use S. woodiana. This latter concept seems to be correct, and we follow this point of view in the present study. Type: Not traced but pictured by Griffith and Pidgeon (1833): Pl. 21, Fig. 3 55 .
Ob' River basin in Western Siberia 17 ; countries of Northern, Eastern and Western Europe 3 ; introduced in Lake Kenon 70 and the Upper Amur Basin in Transbaikalia. A BLASTn search reveals that the non-native population in the Upper Amur Basin shares a widespread COI haplotype that was recorded from the Dnieper Basin in Ukraine, Danube River in Slovakia, and Poland 70,71 .
Comments: Here, we follow the traditional concept of this species 6,70,71 . The correct lists of synonyms are given by Graf 6 and Klishko et al. 70 .