Genotypic Variability of Acer negundo L. along the Trans-Siberian Railway

Abstract

The study of intraspecific variability of alien plants is crucial for revealing the patterns of their microevolution in the secondary distribution range and predicting the possibility of further dispersal and the ability to invade natural plant communities. It is still unclear how a genetically impoverished initial invasive population forms a taxon with a range exceeding the natural range of the species and, therefore, adapts to more diverse ecological and climatic conditions. Boxelder maple, Acer negundo L., is a remarkable object of study in this respect. The secondary distribution range of this North American species covers all regions of our planet excluding Antarctica. In Russia, it spread from Kaliningrad to Vladivostok, formed invasive populations in all eight Federal Districts, and was included in the TOP 100 of the most aggressive invasive species of the country. The intraspecific variability of its biomorphological characters was studied by us earlier, and the results of the study of genotypic variability are presented in this article. Invasive populations of A. negundo located along the Trans-Siberian Railway from Moscow to Vladivostok (9288 km) were examined. We isolated DNA from 38 specimens collected along the Trans-Siberian railway in Vladimir and Kostroma oblasts, the Republic of Tatarstan, Perm Territory, Novosibirsk Region, Krasnoyarsk Territory, Amur Region, and Primorskii Territory. By the ITS 1–2 nuclear DNA site, specimens of Acer negundo from the Russian part of the secondary distribution range showed very high similarity to each other, but with 100% bootstrap support differed from specimens from the natural distribution range. According to the chloroplast high-variable trnL–trnF site, the specimens were divided into two clades that weakly correlated with the geographical origin of the specimen. Separate subclades with high bootstrap support were formed by the plants (1) from Tatarstan (Kazan and Nizhnekamsk) and (2) from Perm and Novosibirsk and (3) samples from Krasnoyarsk. The haplotype network constructed at the trnL–trnF site also demonstrated the genetic specificity of the samples from Tatarstan. We hypothesized that only a few genotypes of A. negundo with a high degree of invasive activity were dispersed along the Trans-Siberian Railway (and possibly throughout all Russia). Other genotypes, including those that entered the territory of the former Russian Empire earlier, have not shown the ability to invade natural plant communities and occur rather rarely.