On the incongruences between phylogenies inferred from nuclear ITS and organellar markers in the Rhabdoweisiaceae (Bryophyta)

Previously, the family Rhabdoweisiaceae was found to combine unexpectedly morphologically diverse lineages of Dicranidae, earlier classified in at least five families. Here we compare phylogenetic reconstructions of the family based on the nuclear ITS region and organellar sequence data, which reveal numerous cases of supported incongruence. Cases of supported conflict between ITS1 and ITS2 include (i) the previously detected lineage ‘Brideliella wahlenbergii C’ that combines ITS1 of Symblepharis sinensis with ITS2 and organellar sequences of Brideliella; (ii) Cynodontium asperifolium and C. tenellum that group with Dicranoweisia cirrata and Captodontium cryptodon in the ITS1 based tree, while ITS2 and organellar data suggest their affinity with Cynodontium; and (iii) Kiaeria falcata that forms a supported clade with the representatives of the R3 major clade of Rhabdoweisiaceae (Cynodontium and Arctoa) based on the ITS1 sequences, while topologies inferred from the ITS2 and organellar data place it in the Kiaeria (R2 clade). In addition, at least six cases of supported conflict between topologies based on nuclear ribosomal ITS and organellar data appeared: (i) Cynodontium suecicum combines organellar sequences identical to those of C. tenellum with ITS sequences of Arctoa blyttii; (ii) Cynodontium asperifolium has an ITS sequence identical to that of C. tenellum while their organellar sequences differ; (iii) Notocynodontium parvulum is indistinguishable from South American lineages of Arctoa pumila in the ITS-based trees, while organellar data suggest its affinities within another major clade of the family; (iv) Eucamptodon perichaetialis appears in an orphaned position in the ITS-based trees, while in the organellar tree it is nested within the Arctoa starkei clade; (v) austral taxa Kiaeria robusta and K. lewinskyae from Australia and New Zealand are found in the Arctoa clade in the ITS-based trees vs. affinity with Kiaeria suggested by the organellar data; and (vi) Arctoa glacialis groups with Ripariella riparia in the ITS-based trees, while in the organellar tree it forms the first-split clade within Arctoa. All these cases of incongruence suggest hybridization among sympatrically distributed taxa. The origin of at least three strongly morphologically deviating lineages of Rhabdoweisiaceae occupying contrasting environments is also underlied by cyto-nuclear discordance.