Invasive species of Erigeron sect. Conyza in the Mediterranean and their hybridogenic activity.
All taxa of Erigeron sect. Conyza are invasive in the Mediterranean basin. Three species, E. bonariensis, E. canadensis, and E. sumatrensis, are the most widespread in Italy, Spain, and Portugal. Based on analysis of the morphological features (the shape and the diameter of inflorescences, the degree of the pubescence of the shoots and leaves), several individuals could not be attributed to any species, since they had intermediate parameters. A hypothesis on the hybridogenic origin of these plants was advanced. The hybridogenic activity of Erigeron sect. Conyza in the secondary distribution range was studied molecular genetically analyzing the ISSR fragments and ITS site of nuclear DNA. All Erigeron invasive species have very low hybridogenic activity, and plants with intermediate traits are not always hybrids.