Habitat conditions of molluscs in the valleys of the Talaya and Bartat Rivers (Krasnoyarsk forest steppe,Russia) in the middle and late-Holocene

Abstract

Here we have analysed the Holocene mollusc successions in the valleys of the Talaya and Bartat rivers (Krasnoyarsk forest-steppe), which, based on three radiocarbon dates, cover at least the last 6000 years. By studying more than 8700 mollusc shells, we aimed to reconstruct the development of alluvial conditions. Existing palynological data from the nearby Eleneva Cave provide deeper insights into the reconstruction of habitat conditions. A total of 13 freshwater and 18 terrestrial mollusc species were identified. Some of the land snail species are the first records for the region, with the finding of Vertigo substriata pushing its distribution limit eastward. The Talaya sequence consisted of five successional stages recognised based on Coniss analysis. The major successional pathway in the mollusc record reflects an increase in temperature and fluctuations in precipitation during the Middle Holocene. Over time, an abundant assemblage of freshwater molluscs was gradually replaced by the dominance of open-country and wetland terrestrial snails. In contrast, cooling at the beginning of the Late-Holocene resulted in a reduction in terrestrial snail species diversity at the expense of aquatic molluscs, again indicating increased moisture in riparian habitats. Although the Bartat River succession covered only the last 600 years, it showed a fairly stable mollusc community composition with some terrestrialization observed in the most recent part of the succession.