Polymorphism of alien Erigeron canadensis L. (Asteraceae) along the Trans-Siberian Railway
Transport corridors serve as one of the main vectors of plant invasion over long distances. The Trans-Siberian Railway, connecting two parts of the world with a different set of native species, is a unique research object for analyzing the distribution of alien plants on a global scale. The invasive species of North American origin, Erigeron canadensis L., found throughout the Trans-Siberian Railway has been set as a model object. This species grows directly on the railway track and on the adjacent slopes, therefore, its spreading is likely along the transport corridor, but not repeatedly from settlements located nearby the railway. All plants have been divided into three haplotypes in accordance to the structure of chloroplast DNA sites (rpl32-trnL and trnL-trnF). The first two haplotypes are represented in the samples from European Russia, the third one includes all samples from the Urals, Western Siberia, the Far East, and all the rest of material collected in European part of Russia. These data confirm our hypothesis about the leading role of the Trans-Siberian Railway in the distribution of E. canadensis in Russia from west to east. However, the isolated haplotypes indicate a low degree of polymorphism of the studied genome regions of E. canadensis. Therefore, its successful invasion is mainly associated with modification variability.