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

According to one of the hypotheses, the success of invasive species is due to increased hybridization processes in the secondary distribution range. The purpose of the study is to predict the rate of hybridization in goldenrod taxa (Solidago L.) formed in the natural phytocenoses, which were formed in the secondary distribution range, and test the hybrid nature of these taxa by experimental and molecular genetic methods, as well as to test the hypothesis of higher competitiveness and invasive activity of hybrids with relation to parental species. For comparison, an analysis, based on data obtained earlier, is conducted of the hybridogenic activity of some other representatives of Asteraceae of North American origin (Bidens spp., Erigeron sect. Conyza spp.). It is shown that not all taxa with intermediate morphological characters are hybrids. So, neither experimental, nor molecular genetic methods confirmed the hybrid origin of "Bidens x garumnae" and "Solidago canadensis x S. gigantea". Solidago x niederederi, S. x snarskisii and Conyza x rouyana hybrids that have arisen in Europe are found only in the secondary distribution range of parental species; they are singly and less competitive than their ancestral forms. The tendency to naturalization is observed only in S. x niederederi. Thus, the hypothesis of higher competitive ability and invasive activity of hybrids as compared to the parent species is not comprehensive, and supporting examples are the exception.