The systematic status of Plagiochila sects. Bidentes Carl and Caducilobae Inoue (Hepaticae) inferred from nrDNA ITS sequences

Plagiochila section Bidentes Carl was erected for some of the tiniest species of the genus that often possess caducous or fragmenting leaves. Current discussions focus on whether P sect. Bidentes represents a natural species group or should be broken up into two lineages, P sect. Bidentes s.str. and P sect. Caducilobae Inoue. Phylogenetic analyses of nrITS sequences of 28 species of Plagiochila produced several independent lineages that correspond with morphologically and phytochemically defined sections of Plagiochila (i.e., P. sects. Arrectae, Fuscoluteae, Glaucescentes, Hylacoetes, Plagiochila, Rutilantes, and Vagae). Plagiochila bidens, the type of P sect. Bidentes, is placed in a clade with several members of P sect. Arrectae Carl; therefore, P sect. Bidentes is treated as a synonym of P sect. Arrectae. The type of P sect. Caducilobae, P caduciloba H.L. Blomq., as well as several other members of the "Bidentes/Caducilobae-complex", cluster with members of P sect. Rutilantes Carl, a group to which can therefore be assigned the majority of species currently placed in P sect. Bidentes, i.e., excluding the type. Morphologically, members of P sect. Rutilantes are characterized by a "free" perianth. In contrast, the members of P sect. Arrectae usually possess perianths that are covered by bracts at least in the basal half. Plagiochila loriloba Herzog ex Carl [syn.: P cuneata var. loriloba (Herzog ex Carl) Herzog] is recognized at the rank of species.