The liverwort genus Metzgeria (Jungermanniopsida) in Europe – An integrative taxonomic update

Species delimitation in liverworts, such as Metzgeria , is hampered by their limited morphology and hence morphologically determined specimens often turn out to belong to other taxa using molecular data. Metzgeria is a simple thalloid liverwort genus with over 100 species and a worldwide distribution. Seven species are listed to occur in Europe. We used three plastid markers ( trnL‐F , rps4 , rpl16 ) and 126 Metzgeria specimens to test the phylogenetic position of European Metzgeria species and to re‐evaluate morphological traits used in species circumscriptions in an integrative manner. We confirmed five taxa, Metzgeria conjugata , M. furcata (with two varieties), M. leptoneura (for Madeira and the Azores only), M. pubescens , M. simplex (as a variety of M. conjugata ) and formally introduce M. curviseta , M. scyphigera and M. azorica sp. nov. for the European flora. Specimens morphologically determined as M. temperata fall either in the M. scyphigera clade or form a well‐separated clade. Further, we tackle the long‐standing nomenclatural issue of M. fruticulosa auct. non (O.F.Müll.) A.Evans by providing the new name Metzgeria aeruginosa comb. & stat. nov. Metzgeria thus includes nine species in Europe, for which an updated identification key is provided, which should aid in morphological species determination of this simple thalloid liverwort in Europe.