Goodbye or welcome Gondwana?: insights into the phylogenetic biogeography of the leafy liverwort Plagiochila with a description of Proskauera gen. nov (Plagiochilaceae, Jungermanniales)

Molecular phylogenies based on chloroplast gene rps4 sequences and nuclear ribosomal ITS sequences have been generated to investigate relationships among species and putative segregates in Plagiochila (Plagiochilaceae), the largest genus of leafy liverworts. About a fourth of the ca. 450 accepted binomials of Plagiochilaceae are included in these phylogenetic analyses, several represented by multiple accessions. A clade with Chiastocaulon, Pedinophyllum, and Plagiochilion is placed sister to a clade with numerous accessions of Plagiochila. Plagiochila pleurata and P. fruticella are resolved sister to the remainder of Plagiochilaceae and transferred to the new Australasian genus Proskauera which differs from all other Plagiochilaceae by the occurrence of spherical leaf papillae. The historical biogeography of Plagiochilaceae is explored based on the reconstructions of the phylogeny, biogeographic patterns and diversification time estimates. The results indicate that the current distribution of Plagiochilaceae cannot be explained exclusively by Gondwanan vicariance. A more feasible explanation of the range is a combination of short distance dispersal, rare long distance dispersal events, extinction, recolonization and diversification.