Naturalized Alien Species in the Floras of the Middle Part of European Russia: Homogenization or Differentiation?

Abstract

Human activities, including biological invasions, cause large-scale changes in the distribution of organisms, one of the consequences of which is biotic homogenization, revealed to various degrees for different biotic groups. Russian researchers use the term “unification of biota” to explain the increase in taxonomic similarity between regions as a result of invasions, but there are no quantitative estimates of this phenomenon. The change in the similarity or difference between regional floras taking into account the alien species naturalized in them is estimated for the regions of the middle part of European Russia by comparing the Jaccard similarity coefficients. Inclusion of the naturalized plant species in the floras increases their distinctions owing to differentiated naturalization depending on natural conditions. However, the presence of different structural groups has different effects on the similarity/differences between the floras. The annual/biennial species have a greater homogenizing effect unlike the herbaceous perennials and tree species, as well as the species biogeographically associated with the analyzed floras, unlike the species alien to European Russia (with their natural distribution ranges beyond the territory of European Russia). The analysis does disagrees with the opinion of Russian authors on unambiguous “unification of biota” as a result of alien species introduction and confirms the view of some researchers that biotic homogenization is not an inevitable fact in biological invasions.