The freshwater oligochaete Branchiura sowerbyi Beddard, 1892 is an alien species exhibiting a rapid range expansion. It has been documented across Africa, Asia, North America, and Europe. In Russia, the species has been found since 2014. In the presented study, the molecular genetic data of B. sowerbyi individuals were obtained for the first time from water bodies in Russia and their genetic diversity was compared with published data from other infested and native countries to infer potential invasion pathways. Analysis of the cytochrome c oxidase subunit I (cox1) gene sequence revealed three related genetic groups within the species. Only one of these groups, including specimens from Russia, is distributed worldwide. The appearance of the species in Russia is likely the result of recent penetration as the result of invasion from the Indo-Chinese region and from already inhabited European countries with the Black Sea basin being a probable invasion corridor.
