The current spread of some invasive neophytes along the lower course of the Siret river

Abstract

In this paper, we present new data on eight species of neophytes of North American origin (i.e., Bidens frondosa, Euphorbia glyptosperma, Fraxinus pennsylvanica, Lepidium densiflorum, Oenothera depressa, O. suaveolens, Oxalis dillenii, and Parthenocissus inserta), whose spread in the lower course of the Siret river proved to be much wider than was previously known in the literature. All of these species are invasive in natural and anthropogenic habitats, on both banks of the river. Two of them were introduced deliberately in Romania, as ornamental plants (Fraxinus pennsylvanica and Parthenocissus inserta), while the other 6 species were introduced accidentally. Euphorbia glyptosperma and Oenothera suaveolens are reported here for the first time in the historical province of Muntenia, and other species are floristic novelties for counties of Vrancea (Bidens frondosa, Fraxinus pennsylvanica, Oenothera depressa) and Brăila (Fraxinus pennsylvanica and Oxalis dillenii). In addition to current spread of these species along the lower course of the Siret River, the paper provides data on the types of habitats invaded by each of them.