Taxonomic Evaluation of Hedera crebrescens: A Potentially Invasive Ivy in Central Europe

Although Hedera helix is the only native ivy distributed in Central Europe, other ivy species are cultivated in this region and have horticultural importance, including H. hibernica, H. colchica, and H. azorica. On the basis of morphological, cytological, and phenological studies, a newly identified diploid species of ivy, H. crebrescens Bényei-Himmer & Höhn, was recently described from Hungary. Due to its high reproductive capacity and vigorous growth, this species can be considered a potentially invasive plant that could readily supplant H. helix in its native habitats. To characterize the molecular taxonomic status of H. crebrescens, we conducted a molecular genetic analysis based on five chloroplast and one nuclear DNA regions. Our phylogenetic reconstruction supported the monophyly of Hedera, with a tree topology similar to that previously obtained based on phylogenetic cpDNA analyses. Mediterranean species of ivy were well separated from the remainder of the European species, as well as from Asian species. Hedera crebrescens represented a single independent haplotype within the Asian–European cluster, whereas H. helix proved to be polyphyletic. The detected species-specific haplotype and invariability among studied specimens obtained from different geographical locations, provide support for the taxonomical autonomy of H. crebrescens.