The various existing definitions of monophyly have resulted in confusion within the systematics community. The divergence in terminology started with the work of Willi Hennig who attempted to introduce a precise definition of phylogenetic relationship in 1950, a term that he had synonymised with monophyly by 1953, thereby creating a new definition. In 1965, Hennig introduced paraphyly to distinguish his version of monophyly from groups based on symplesiomorphies or stem groups. In attempting to resolve the confusion, Ashlock synonymised Hennig’s monophyly as holophyly, resulting in another new term. Ashlock, Mayr and others defended Haeckel’s original use of monophyly, by including holophyly and paraphyly. The result was an unresolved 21-year debate on monophyly and its various uses. A review of the history of monophyly and the origins of its various definitions has resulted in two new terms to distinguish the different versions of monophyly currently in use: diamonophyly, which group definitions based a notion of ancestor-descendant relationships, and synmonophyly, which groups definition based on kinship relationships. The terms ‘reciprocal monophyly’ and ‘oligophyly’ are discussed as being diamonophyletic.

Recent molecular studies have redefined families and genera within the anthocerotes, but species boundaries are only now being revised. Monophyly of Australian and New Zealand taxa within the genus Megaceros Campb., which share the same spore and similar gametophyte morphology, was assessed. On the basis of sequence data, mainland Australian lineages are not monophyletic but are interspersed with New Zealand lineages. There are three species present in Australia, including the common and widespread M. gracilis (Reichardt) Steph., the widespread tropical M. flagellaris (Mitt.) Steph., recognised by its tesselated spores, and a new species, M. austronesophilus, found only in Tasmania and Macquarie Island. None of the currently recognised New Zealand taxa is conspecific with any of the Australian taxa. However, New Zealand lineages were found to be genetically and morphologically more diverse than is currently recognised.

The present study investigated the hypothesis that several fern species occurring in Macaronesia and Atlantic Europe are relicts of the Miocene Paratethyan–Tethyan flora that survived in Macaronesia refugia. The hypothesis was tested by reconstructing the phylogenetic relationships of the derived fern Davallia canariensis, which is the only species of a mainly South-east Asian family, Davalliaceae, occurring naturally in Europe, Macaronesia and northern Africa. The dataset comprised a comprehensive taxonomic sampling of the family, with representatives of the five major lineages and ∼50–60% of the extant species diversity. For each species, we included two coding regions of the chloroplast genome, namely, atpB and rbcL. Diversification times were estimated considering previous estimates of the crown and stem group age as well as the fossil record of Davalliaceae. The results were consistent with the hypothesis, by recovering D. canariensis as the only extant member of an isolated lineage that has been separated from other crown group Davalliaceae since the Late Miocene. The obtained results are discussed in the context of the Messinian salinity crisis, evolution of epiphytic habit in ferns, and the generic classification of Davalliaceae.

Phylogenetic analyses of a three-marker dataset of Lejeuneaceae (chloroplast genome rbcL gene and trnL–trnF region, and nuclear ribosomal ITS1–5.8S-ITS2 region) resolve Lejeunea huctumalcensis (synonym Ceratolejeunea dussiana) in a well supported lineage with Physantholejeunea portoricensis. Representatives of Lejeunea and Ceratolejeunea form independent lineages. Physantholejeunea and L. huctumalcensis share the presence of ocelli, pycnolejeuneoid innovations and keeled perianths, with keels forming horn-like projections. On the basis of the molecular phylogenetic and morphological evidence, we transfer L. huctumalcensis to Physantholejeunea.