New insights into the phylogeny and relationships within the worldwide genus Riccardia (Aneuraceae, Marchantiophytina)

With 280 accepted species, the genus Riccardia S.F.Gray (Aneuraceae) is one of the most speciose genera of simple thalloid liverworts. The current classification of this genus is based on morphological and limited-sampling molecular studies. Very few molecular data are available and a comprehensive view of evolutionary relationships within the genus is still lacking. A phylogeny focusing on relationships within the large genus Riccardia has not been conducted. Here we propose the first worldwide molecular phylogeny of the genus Riccardia, based on Bayesian inference and parsimony ratchet analyses of sequences from three plastid regions (psbA-trnH, rps4, trnL-F). The results support the monophyly of Riccardia and a new monospecific genus, Afroriccardia Reeb & Gradst. gen. nov., is described based on molecular and morphological evidence. The results indicate that several currently recognized infrageneric divisions and a few species are not monophyletic, suggesting that further analyses are needed to arrive at a proper understanding of the phylogeny of the genus. Although evidence for an Andean clade was found, most of the species appear scattered in different clades without clear geographical segregation. Broader sampling and further analyses are necessary in order to improve our understanding of the phylogeny of this poorly known liverwort genus.