The systematic position of Plagiochila (Jamesoniella) dependula (Jungermanniopsida) inferred from nrITS sequences and morphology, with notes on its differentiation from Plagiochila fuscolutea

Based on morphology and phylogenetical analyses of nrITS sequences, the Andean endemic Plagiochila (Jamesoniella) dependula is placed in Plagiochila sect. Fuscoluteae. Perianths, oil bodies and sporophytes are described for the first time. Morphologically, P. dependula is characterized by entire, dorsally mostly shortly decurrent, laterally appressed, reniform leaves which are covered by irregular papillae and membranous wax platelets, papillose oil bodies, intercalary androecia with opposite bracts that overlap dorsally, a plagiochilid perianth with an entire mouth, a 250 μm thick capsule wall with thickenings in all layers, large 1-4 celled spores, and bispiral elaters. Morphotypes of Plagiochila fuscolutea with laterally appressed leaves differ from P. dependula by an at least moderately decurrent, broad dorsal leaf base, a ± smooth upper leaf surface, and by its often toothed leaf apices. Plagiochila wolframii is placed in the synonymy of P. fuscolutea. Maximum likelihood and parsimony analyses of 29 Plagiochila ITS sequences resolve P. dependula in a well-supported clade with several other representatives of P. sect. Fuscoluteae. Branch lengths within sect. Fuscoluteae point to a sudden diversification. Accessions of P. heterophylla s.str. from Great Britain (formerly known as P. atlantica) and Costa Rica form an unsupported monophyletic lineage.