Recent Introduction or Evidence for a Northern Dispersal Corridor Between East and Central Asia? the Case of Radix Plicatula

The freshwater fauna of Central Asia is largely composed of widespread Eurasian taxa and shares little overlap with the highly endemic assemblages of Southeast Asia. Here, the first record of the East Asian pond snail Radix plicatula (W. H. Benson, 1842) in Central Asia (northern Tien Shan, Kazakhstan) is reported, extending its known range by approximately 2,200 km. To assess the origin of this population, morphological data, genetic analysis, and species distribution modeling were combined. Phylogenetic analyses place the Tien Shan specimens within the main Radix plicatula lineage, whereas haplotype data reveal unexpectedly high genetic diversity within a geographically restricted area. These results are compatible with two alternative scenarios—a recent introduction and an older colonization event—although the observed genetic diversity appears more consistent with long-term persistence in the region. Species distribution models produced contrasting results depending on background selection. Models with unrestricted backgrounds predicted a range largely confined to East and Southeast Asia, whereas models with spatially constrained backgrounds and land-cover variables indicated substantially broader suitability, including Central Asia. This discrepancy suggests that the present-day distribution of Radix plicatula is not solely determined by climate. Paleoclimatic projections indicate that suitable habitats were more widespread in the past, forming a belt north of the major Asian mountain systems. Together with the molecular evidence, this suggests a scenario of Pleistocene dispersal between Southeast and Central Asia. Highlights An East and Southeast Asian freshwater snail was discovered far beyond its known range in Central Asia. Genetic structure reveals unexpectedly high diversity, favoring an older colonization scenario over a recent introduction. Ecologically realistic models predict a much broader potential range than is currently observed. Paleoclimatic projections suggest past connectivity north of the major Asian mountain systems. Results support the hypothesis of a previously overlooked dispersal pathway linking East and Central Asia.