Hybridization as a Factor of Invasive Activity of Alien Goldenrod Species (Solidago)

Abstract

According to one hypotheses, the success of invasive species is due to increased hybridization processes in the secondary distribution range. The purpose of the study was to predict the further rate of the introduction of goldenrod taxa (Solidago L.) in the natural phytocenoses that form in the secondary distribution range with verification of the hybrid nature of these taxa via experimental and molecular genetic methods and to test the hypothesis of higher competitiveness and invasive activity of hybrids with relation to parental species. For comparison, an analysis of the hybridogenic activity of some other representatives of the Asteraceae family of North American origin (Bidens spp., Erigeron sect., Conyza spp.) based on data previously obtained by the authors. It is shown that not all taxa with intermediate morphological characters are hybrids. Thus, neither experimental nor molecular genetic methods confirmed the hybrid origin of Bidens × garumnae and Solidago сanadensis × S. gigantea. Hybrids Solidago × niederederi, S. × snarskisii, and Conyza × rouyana, which have arisen in Europe. They are found only in the secondary distribution range of parental species and are solitary and less competitive than their ancestral forms. A tendency to naturalize is observed only in S. × niederederi. Thus, the hypothesis of the higher competitive ability and invasive activity of hybrids as compared to parental species is not comprehensive, and its supporting examples are the exception rather than the rule.