The taxonomic position and lectotypification of Frullania diversitexta Steph. (Frullaniaceae, Marchantiophyta) and its synonyms, with notes on the placement of F. ignatovii Sofronova, Mamontov & Potemkin

Frullania diversitexta Steph. currently occupies its own subgenus, subg. Diversitextae (Kamim.) S.Hatt., although its taxonomic placement is somewhat enigmatic. The habit of the species, as well as the position and shape of the lobules, are morphologically comparable to species in subg. Diastaloba Spruce and subg. Frullania Spruce, whereas its tuberculate perianth ornamentation is reminiscent of species in subg. Trachycolea Spruce. Here, molecular sequence data resolves F. diversitexta within subg. Trachycolea in a relationship with F. plana Sull. (sect. Planae R.M.Schust.). Frullania diversitexta and F. plana have a similar branching pattern, leaf lobe shape, leaf cell areolation, stylus, lobule position, underleaf shape and primary branch appendages that often have two saccate lobules. Differences in their lobule shape, sexuality, position of the gynoecia and perianth ornamentation, however, decidedly warrant the placement of F. diversitexta in its own section, sect. Diversitextae (Kamim.) J.J.Atwood, Vilnet & Mamontov, stat. nov. Lectotypes are designated for F. diversitexta and its three synonyms: F. abducens Steph., F. sendaica Steph. and F. tosana Horik. (replaced synonym of F. tenella Steph., hom. illeg.). Frullania ignatovii Sofronova, Mamontov & Potemkin, having obovoid, skull shaped lobules with an unusual bilabiate mouth, is also resolved within subg. Trachycolea, in a sister relationship with F. davurica Hampe and F. jackii Gottsche.