Reinstatement of Plagiochila maderensis (Jungermanniopsida : Plaglochilaceae) based on chemical evidence and nrDNA ITS sequences

Plagiochila maderensis Gottsche ex Steph. is reinstated as a Madeiran endemic. This taxon was synonymized with P. spinulosa (Dicks.) Dumort. over 35 years ago and has been accepted under that name in recent years. Morphologically, P. maderensis, which is known only in the sterile state, differs from P. spinulosa in having a smooth leaf surface, larger leaf cells and an often broadly truncate leaf apex. Phytochemical analysis using NMR and GC-MS profiling demonstrated that the lipophilic secondary metabolites are strikingly and unambiguously distinct from those of P. spinulosa. The dominant constituent is 4-hydroxy-3'-methoxybibenzyl, present in exceptionally large amounts. Analysis of the ITS region of nrDNA of P. maderensis and incorporation of the sequence into a maximum likelihood analysis of a dataset comprising another 28 Plagiochila and two outgroup sequences revealed that P. maderensis is a member of Plagiochila sect. Rutilantes Carl. Plagiochila maderensis is placed sister to the Neotropical species P. gymnocalycina (Lehm. & Lindenb.) Mont. and P. trichostoma Gottsche, but in a clade that does not have bootstrap support. It is known already that 4-hydroxy-3'-methoxybibenzyl is the principal bibenzyl constituent of P. trichostoma and chemical analysis has now shown that this applies also to P. gymnocalycina.