Biogeography ofPlagiochila(Hepaticae): natural species groups span several floristic kingdoms

Abstract

AbstractAimThis paper presents a synthesis of our recent results regarding the biogeography ofPlagiochilausing a molecular approach, and documents intercontinental ranges within this largest genus of the hepatics.MethodsA maximum likelihood analysis of sixty‐one nrITS sequences ofPlagiochilawas performed and the molecular topology obtained was compared with morphological, phytochemical and geographical data.ResultsOur molecular data set allowed the identification of elevenPlagiochilasections, the majority of which cover at least two floristic kingdoms. Seven sections have species in Europe (sect.Arrectae,Carringtoniae,Fuscoluteae,Glaucescentes,Plagiochila,Rutilantes,Vagae).Plagiochilaspecies from Atlantic Europe are usually close to or conspecific with neotropical taxa, whereas species widespread in Europe are closely related to Asian ones and not to those in the Neotropics.Plagiochilasect.Arrectaerepresents a neotropical – Atlantic European clade. The section is not closely related – as has often been suggested – to the morphologically similar sect.Zonataefrom Asia and western North America. Sequence data show that the AfricanP. integerrimaand the neotropicalP. subplanaare members of the Asian sect.Cucullatae(sect.Ciliatae, syn. nov.), which becomes pantropical in distribution. An ITS sequence ofP. boryanafrom Uganda confirms the Afro‐American range of the primarily neotropical sect.Hylacoetes. Similarities in sporophyte morphology between the sect.Cucullataeand sect.Hylacoetesare the result of parallel evolution.Main conclusionsOur results indicate that intercontinental ranges at section and species level are common inPlagiochila.Carl's (1931)subdivision ofPlagiochilainto sections restricted to one floristic kingdom is outdated. Biogeographical patterns inPlagiochilaare not dissimilar to those of other groups of bryophytes but elucidation of the geographical ranges of the taxa requires a molecular approach.Contrary to earlier belief, mostPlagiochilaspecies from Atlantic Europe do not have close relatives in Asia but are conspecific with or closely related to species from tropical America.