Molecular circumscription, intrafamilial relationships and biogeography of the Gondwanan liverwort family Pallaviciniaceae (Hepaticophytina, Bryophyta) Studies in austral temperate rain forest bryophytes 27 F. Schaumann, W. Frey, T. Pfeiffer, and M. Stech Freie Universita¨t Berlin, Institut fu¨ r Biologie, Systematische Botanik und Pflanzengeographie, Berlin, Germany Received June 2, 2004; accepted November 23, 2004 Published online: March 15, 2005 Ó Springer-Verlag 2005 Abstract. Maximum parsimony and maximum likelihood analyses based on partial trnL intron sequences of 60 specimens of the Gondwanan liverwort family Pallaviciniaceae, and 23 repre- sentatives of other families of the Metzgeriidae, resolve the Pallaviciniaceae as monophyletic, albeit with low bootstrap support, with the Hymenophytaceae as their sistergroup in the likelihood tree. These data and further analyses of the Pallaviciniacean taxa only, based on the trnT UGU -trnL UAA spacer, trnL UAA 5¢exon and trnL UAA intron of the chloroplast DNA and the ITS2 of the nuclear ribosomal DNA, support a separation of Moerckia (Moerckioideae) from the remaining genera. An unexpected close relation- ship between Podomitrium (Podomitrioideae) and the Symphyogynoideae is observed, whereas Pallavicinia and the Pallavicinioideae are poly- phyletic. Within Symphyogyna, well-supported clades comprising the species with dendroid and prostrate-lobate thalli on the one hand and species with prostrate-undivided thalli on the other hand (except S. tenuinervis, including Symphyogynopsis) are distinguished. According to the molecular data, evolution of the dendroid life-form occurred three times independently in the Metzgeriidae, in Symphyogyna, Jensenia, and Hymenophyton. Key words: Pallaviciniaceae, Hymenophytaceae, molecular relationships, trnT UGU -trnL UAA spacer, trnL UAA intron, ITS2, biogeography. The Pallaviciniaceae comprise thalloid hepa- tics that are thought to represent an archaic liverwort group, based on peculiar character- istics such as an apical cell (lenticular in cross section) with two lateral cutting faces, the latero-ventral branching modes, presence of a central strand, and the at least superficial similarity with Pallaviciniites devonicus (Hue- ber) R.M. Schust. from mid-Devonian time (Schuster 1992). The extant species of the family are almost exclusively distributed in the tropics, subtropics, and in temperate regions of the Southern Hemisphere, with centers of diversity in South America and Australasia. Ten genera have so far been described (Schuster 1992, Crandall-Stotler and Stotler 2000) and grouped into four subfamilies Plant Syst. Evol. 252: 27–48 (2005) DOI 10.1007/s00606-004-0279-z