Evaluation and comparison of the genetic structure of Bunias orientalis populations in their native range and two non-native ranges

We studied the invasive warty cabbage Bunias orientalis (Brassicaceae) in three geographically distinct areas. Using inter-simple sequence repeat fingerprinting, we analyzed warty cabbages, including non-native populations, from the eastern Baltic and western Siberian regions and native populations from southwestern Russia. The eastern Baltic region and western Siberia represent the two opposite directions of B. orientalis spread in climatically different zones. The genetic structures of the native and non-native B. orientalis populations were assessed through analysis of molecular variance (AMOVA) and the Bayesian clustering method and by determining the main measures of genetic diversity. AMOVA revealed considerable population differentiation in both the native and invasive ranges. Our results did not indicate a decrease in genetic diversity in the non-native populations of B. orientalis. Similar measures of genetic diversity and genetic structure were determined in the invasive populations in two geographically and ecologically distinct, non-native regions located in Europe and Asia. In both of these regions, higher genetic diversity was detected in the non-native populations than in the native region populations, which may be due to multiple introductions. However, Bayesian clustering analysis revealed slightly different sources of invasive populations in the two non-native regions. Genetic diversity patterns revealed the lack of isolation by distance between populations and confirmed the influence of anthropogenic factors on the spread of B. orientalis. The significance of native populations as germplasm resources for breeding is discussed.