Reptile occurrences data in the Volga River basin (Russia).

BACKGROUND: The Volga basin is one of the most industrially-developed regions of Russia with a high degree of anthropogenic impact on natural ecosystems. Human influence negatively affects the species diversity and number of animals, including reptiles. There are no endemic species in the reptile fauna of the Volga basin. The herpetofauna of the region makes up 25% of the reptile fauna of Russia (Dunaev and Orlova 2017). We began to study the fauna of reptiles and their distribution in the Volga basin in 1988. Although we registered 20 reptile species in the Volga basin to date, apparently this is not a complete list of species in the region (Bakiev et al. 2004, Bakiev et al. 2009a, Bakiev et al. 2015, Kirillov et al. 2020). The distribution of reptiles in this region is not fully understood. NEW INFORMATION: Our dataset contains information on reptile occurrences in the Volga River basin. The dataset is based on original research by the staff of the Laboratory of Herpetology and Toxinology and Laboratory of Population Ecology of the Institute of Ecology of the Volga River basin of the Russian Academy of Sciences and Joint Directorate of the Mordovia State Nature Reserve and National Park "Smolny". A total of 5,086 occurrences of 20 species are published for the first time with georeferencing. Many of these reptiles are listed in regional Red Data Lists. The European Pond Turtle Emys orbicularis (Linnaeus, 1758) is included in the IUCN Red List with the category "Near Threatened".

Mitochondrial phylogeny shows multiple independent ecological transitions and northern dispersion despite of Pleistocene glaciations in meadow and steppe vipers (Vipera ursinii and Vipera renardi).

The phylogeny and historical demography of small Eurasian vipers of the Vipera ursinii and V. renardi complexes were studied using mitochondrial DNA sequences analysed with Bayesian inference, Maximum Likelihood and Maximum Parsimony approaches, and mismatch distributions. Diversification in the group resulted from an initial dispersion in the later Pliocene - Pleistocene in two directions: north-westwards via the Balkans (V. ursinii complex) and north-eastwards from Asia Minor via the Caucasus (V. renardi complex). An independent, comparatively recent transition occurred from montane habitats to lowland grasslands in different mitochondrial lineages during the Late Pleistocene, when representatives of the both complexes had reached lowland steppes to the north. Effective population size showed clear signs of rapid growth in eastern V. renardi, triggered by colonization of vast lowland steppes, but in western V. ursinii complex grew during the Last Glaciation and experienced stabilization in Holocene. Expansion and population growth in lowland lineages of V. renardi was not strongly affected by Pleistocene climatic oscillations, when cold, dry conditions could have favoured species living in open grasslands. The high diversity of closely related haplotypes in the Caucasus and Tien-Shan could have resulted from repetitive expansion-constriction-isolation events in montane regions during Pleistocene climate fluctuations. The mitochondrial phylogeny pattern conflicts with the current taxonomy.