Macroevolutionary versus molecular analysis: Systematics of the Didymodon segregates Aithobryum, Exobryum and Fuscobryum (Pottiaceae)

Abstract

  Molecular analysis has several problems including (1) small samples, (2) radiation of molecular strains or races that separately generate their own species-level lineages, (3) all problems associated with cladistics analysis done using morphological data, (4) conflicting studies, (5) reuse of data contributing to small samples and absence of experimental replication, (6) no native taxon concept, and (7) use of combined data sets to achieve an invented gene history. A macroevolutionary re-interpretation of a recent molecular revision of species of Didymodon s.lat. (Bryophyta) introduces a monophyletic evolutionary model fully compatible with both molecular and morphological data. Multiple molecular races and their contribution to paraphyly and apparent polyphyly are quantized through analysis of recent published studies to demonstrate uncertainty of monophyly on the order of a distance of 4.5 contiguous nodes per species in molecular cladograms. The number of trait changes per speciation event averaged 3.57, on a par with previous studies. This work is the first successful prediction of the actual existence of a missing link, Exobryum rufidulum, hypothetically described in a previous macroevolutionary analysis. For the first time a taxon higher than genus was established based on an extension of the empirical dissilient genus concept. Six new combinations are made in Exobryum. A new genus, Aithobryum, is established with three species transferred from Didymodon. Didymodon sinuosus and D. californicus are transferred to Vinealobryum.