LAUSR

Increases in human activity and climate change are factors that are expected to augment the number and impact of alien species in the northern regions. In the present paper, we report the discovery of a population of Asian Corbicula clams in the North of Russia near the Arctic frontier (64°N, 40°E), which is the most northern record of these invaders in the world. This population contains two distinct lineages that are living in sympatry in a man-made channel of the Arkhangelsk thermal power plant. The first lineage belongs to the morphotype Rlc by shell morphology but reveals the FW5 mtDNA haplotype (COI and 16S rRNA genes), which was typically recorded in the morphotype R. The second lineage reveals the shell morphological pattern of the morphotype R but has the FW17 mtDNA haplotype, which usually occurs in specimens of the morphotype S. Both forms that were identified, based on conchological and anatomical features and differences in mtDNA haplotypes, reveal the same 28S rDNA sequences but show intragenomic nDNA variability with two different variants of the 28S rDNA gene within each individual (allelic sequence heterogeneity). The discrepancy between mtDNA data and shell morphology could be explained by the well-known mechanism that is associated with androgenesis together with “egg parasitism” (mitochondrial genome-capture) in invasive Corbicula clams. The intragenomic 28S rDNA variability may be due to a hybridization event which can join different alleles from the two diploid (or polyploid) parental taxa to an allopolyploid descendant. We found that the lineages that rarely occur in European populations are exclusively established in a population near the Arctic frontier. Moreover, specimens belonging to the R-morphotype with the FW17 mtDNA haplotype that has sporadic occurrences in central Europe is prevalent (> 90% of a total sample) in a mollusk assemblage at the studied site in northern Russia. Additionally, we show that the life span of Corbicula clams in high latitudes may be longer than 1 year. Isolated Corbicula populations in artificially heated or geothermal reservoirs may therefore be primary sources for a broad invasion to seasonal waterbodies of the high-latitude regions in the future as climate warming progresses.