Phylogenetic analysis of Potentilla using DNA sequences of nuclear ribosomal internal transcribed spacers (ITS), and implications for the classification of Rosoideae (Rosaceae)

The circumscription of Potentilla has varied widely. To investigate the monophyly of Potentilla and the phylogenetic relationships of associated genera we used nuclear ribosomal internal transcribed spacer (ITS) DNA sequences. Fourteen species of Potentilla (sensu Wolf 1908) were included, some of which represent proposed segregate genera (such as Argentina, Comarum, Drymocallis, Duchesnea, Pentaphylloides, and Sibbaldiopsis), and 17 other genera of Rosoideae, using Prunus as outgroup. Our most parsimonious tree strongly implies that Potentilla is not monophyletic. Forcing the monophyly of Potentilla yields distinctly longer trees. Several morphological features appear to have evolved several times independently, including the swollen receptacle ("strawberry") and ternate leaves. In order to minimise nomenclatural change and to name only well supported clades, Potentilla should be split into several genera, while other previously recognised genera such as Duchesnea, Horkelia, and Ivesia are best included in Potentilla. We suggest, however, that a phylogenetic nomenclature (sensu de Queiroz & Gauthier 1994) might be a better solution.