Sensitive phylogenetics of Clematis and its position in Ranunculaceae

Ranunculaceae are a nearly cosmopolitan plant family with the highest diversity in northern temperate regions and with relatively few representatives in the tropics. As a result of their position among the early diverging eudicots and their horticultural value, the family is of great phylogenetic and taxonomic interest. Despite this, many genera remain poorly sampled in phylogenetic studies and taxonomic problems persist. In this study, we aim to clarify the infrageneric relationships of Clematis by greatly improving taxon sampling and including most of the relevant subgeneric and sectional types in a simultaneous dynamic optimization of phenotypic and molecular data. We also investigate how well the available data support the hypothesis of phylogenetic relationships in the family. At the family level, all five currently accepted subfamilies are resolved as monophyletic. Our analyses strongly imply that Anemone s.l. is a grade with respect to the Anemoclema+Clematis clade. This questions the recent sinking of well-established genera, including Hepatica, Knowltonia and Pulsatilla, into Anemone. In Clematis, 12 clades conceptually matching the proposed sectional division of the genus were found. The taxonomic composition of these clades often disagrees with previous classifications. Phylogenetic relationships between the section-level clades remain highly unstable and poorly supported and, although some patterns are emerging, none of the proposed subgenera is in evidence. The traditionally recognized and horticulturally significant section Viorna is both nomenclaturally invalid and phylogenetically unsupported. Several other commonly used sections are likewise unjustified. Our results provide a phylogenetic background for a natural section-level classification of Clematis.