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Maximum likelihood analyses based on the internal transcribed spacer region of nuclear ribosomal DNA and the chloroplast protein coding gene rps4were conducted to investigate phylogenetic relationships among species of Plagiochilaand to reconstruct the ranges of natural species groups within the genus. Based on the results of the molecular analyses and on morphological evidence, the tropical African species of Plagiochilaare assigned to the sections Arrectae, Cucullatae, Hylacoetes, Rutilantes, Vagae, and the new sect. Africanae( P. barteri, P. colorans). With the exception of Africanae, all sections possess intercontinental ranges; their centers of diversity are in the tropics. Clade and species diversity in Africa is lower than in other parts of the tropics and may reflect drought periods of the Pleistocene. Intercontinental ranges at specific level exist between tropical America and Africa whereas similarities between tropical Asia and Africa were only recovered at the sectional level. ITS sequence sets were used to test the monophyly of species with intercontinental ranges and to explore the development of the Afro-American range of P. boryana. A well supported clade with accessions of P. boryanafrom Bolivia and Uganda is nested in the robust neotropical Hylacoetes. This topology and the low genetic distance of the different P. boryanaaccessions provide some evidence for long-range dispersal of P. boryanaeastwards across the Atlantic, originating from the Neotropics. An African origin of the Vagaeclade which includes neotropical and paleotropical taxa is suggested by the clustering of accessions from the East African Islands at the base of this clade. In addition, the presented data support the hypothesis of several switches from Africa to Asia and vice versa. A derived clade within Vagaeincludes accessions from the African mainland and the Neotropics. Our results seem to indicate that the extant tropical African Plagiochilaflora is a mixture of old elements and rather recent immigrants.

Plagiochilasection BidentesCarl 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. Bidentesrepresents a natural species group or should be broken up into two lineages, P. sect. Bidentess.str. and P. sect. CaducilobaeInoue. Phylogenetic analyses of nrITS sequences of 28 species of Plagiochilaproduced 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. ArrectaeCarl; therefore, P. sect. Bidentesis treated as a synonym of P. sect. Arrectae. The type of P. sect. Caducilobae, P. caducilobaH.L. Blomq., as well as several other members of the “Bidentes/Caducilobae-complex”, cluster with members of P. sect. RutilantesCarl, 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. Rutilantesare characterized by a “free” perianth. In contrast, the members of P. sect. Arrectaeusually possess perianths that are covered by bracts at least in the basal half. Plagiochila loriloba Herzog ex Carl [syn.: P. cuneatavar. loriloba(Herzog ex Carl) Herzog] is recognized at the rank of species.