An integrative approach to the study of Moerckia (Marchantiopsida: Moerckiaceae), with description of a new genus, Pseudomoerckia, and new family, Pseudomoerckiaceae

ABSTRACT Introduction The genus Moerckia Gottsche belongs to the order Pallaviciniales, the phylogeny of which has been insufficiently studied. We re-evaluate the phylogenetic position of M. blyttii and the importance of certain morphological features, and re-emphasise the differences in morphology, ecology and distribution of M. hibernica and M. flotoviana. Methods DNA data from three nucleotide markers, namely ITS1 to ITS2 nrDNA, trnL–F and trnG intron cpDNA, were obtained from specimens of Moerckia species, including the generitype M. hibernica, which had not been sequenced before. Relationships were explored using maximum parsimony, maximum likelihood and Bayesian analyses. Key results In the results of molecular analyses, specimens of Moerckia hibernica from Ireland and Scotland formed a sister clade to that of M. flotoviana, and M. blyttii retained its distinct position basal to both Moerckiaceae and Pallaviciniaceae. This clarifies the phylogenetic position of M. hibernica as well as that of the Pallaviciniales as a whole. The most significant morphological characters to distinguish M. flotoviana from M. hibernica are placement of antheridial scales, width-to-length ratio of thallus segments, and width of midrib; conducting strands are a less important differentiating feature, being present in both species and often weakly developed. The results showed the variability and overlap of some morphological characters. Conclusion The new family Pseudomoerckiaceae and a new monotypic genus, Pseudomoerckia, created to accommodate Moerckia blyttii, are described. Cordaeaceae Mamontov et al. is synonymised with Moerckiaceae K.I.Goebel ex Stotler & Crand.-Stotl. The species status and restricted distribution of M. hibernica are confirmed.