Evidence for Plio-Pleistocene Duck Mussel Refugia in the Azov Sea River Basins

Abstract

Freshwater mussels (Bivalvia: Unionoida) play an important role in freshwater habitats as ecosystem engineers of the water environment. Duck mussel Anodonta anatina is widely distributed throughout Europe, Siberia, and Western and Central Asia, which makes it a convenient object for biogeographic studies. In this study, we analyzed the divergence of A. anatina populations and discovered a separate genetic lineage distributed in rivers of the Azov Sea basin. This was confirmed by the high genetic distances between this group and previously defined populations, and by the position of this clade in the Bayesian phylogeny calibrated by an external substitution rate. Based on our approximate Bayesian computation (ABC) analysis, biogeographic scenarios of A. anatina dispersal in Europe and Northern, Western, and Central Asia over the Neogene–Quaternary were simulated. The haplogroup’s isolation in the rivers of the Azov Sea basin most likely occurred in the Late Pliocene that was probably facilitated by rearrangement of freshwater basins boundaries in the Ponto-Caspian Region. Population genetic indices show the stability of this group, which allowed it to exist in the river basins of the region for a long time. The discovery of a long-term refugium in the rivers of the Azov Sea led to a better understanding of freshwater fauna evolution in the Neogene–Quaternary and highlighted the importance of conservation of these freshwater animals in the region as a source of unique genetic diversity.

Population structure and gene flow in the Sheepnose mussel (Plethobasus cyphyus) and their implications for conservation

“…The high number of private alleles and unique haplotypes found at each sample location indicate that these locations have been isolated for a substantial amount of time. Similar results have been found in other studies of freshwater mussels (Elderkin et al, 2007; Hewitt, 1996; Inoue et al, 2014; Jones et al, 2015; Tomilova et al, 2020). Together these studies indicate that for many freshwater mussels, population genetic structure is more reflective of long‐term factors related to changes since the Pleistocene era and not from recent anthropogenic causes.…”

Epigean (pond-dwelling) species of the genus Niphargus Schiцdte, 1849 (Crustacea: Amphipoda: Niphargidae) from the coastal plains of the Black and Azov seas of the north- and south-western Caucasus

“…1; Table 1) coincides with earlier molecular genetic data obtained on other invertebrates, which indicate the existence of an ancient Plio-Pleistocene refugium in the deltas of the rivers of the Sea of Azov, where genetically stable populations/species were preserved for a long time (Tomilova et al, 2020). The separation of different phylogenetic lineages in the rivers of the Sea of Azov basin probably occurred in the Late Pliocene (about 3.6-2.6Mya), which probably contributed to the change in the boundaries of freshwater basins in the Ponto-Caspian region (Tomilova et al, 2020).…”

Defining criteria for the reintroduction of locally extinct populations based on contemporary and ancient genetic diversity: The case of the Adriatic Beluga sturgeon (Huso huso)

“…(b) Analyses performed using 73 individuals of three population samples genotyped at 893 SNPs of aquatic species (Kotlik et al, 2008). The current scenario is presumably the result of multiple alternating periods of isolation and interconnection that have occurred in the paratethys in the last 5 million years (Tomilova et al, 2020). The latest natural contact between the two basins dates back to 15.000-11.000 years ago following the last glaciation of the Quaternary (Zubakov, 1988) through For what concerns the two Adriatic haplotypes, no certain conclusion can be brought up about the homogeneity of the extinct population given the low number of museum animals successfully analysed.…”