O'BRIEN, TERRY J. Department of Biological Sciences, Rowan University, Glassboro, NJ 08028, U.S.A. - The dubious origins of pleurocarpous mosses: molecular evidence for the phylogenetic positions of Aulacomnium Schwägr. and Rhizogoniaceae.
A maximum parsimony analysis of a four-gene cpDNA dataset including 55 exemplar taxa
indicates that the Rhizogoniaceae plus Aulacomnium and Calomnion are the
sister group or nearsister group to pleurocarpous mosses, which with 6600 species is
the most diverse clade of extant mosses. The evidence suggests that the traditional
genera of Rhizogoniaceae are a paraphyletic group, consisting of a minimum of 3 clades.
Aulacomnium is a monophyletic group, and its sister lineage includes
Mesochaete. The pleurocarps are comprised of a relatively small
"racopilalean" clade and a large "hypnalean" clade (including
Hookeriales, Hypnales and Leucodontales), a fundamental division that is consistent
with the conclusions by DeLuna et al. and Newton and DeLuna. These results have
implications for our understanding of diversification, adaptation, disparity, development,
and genome evolution of the pleurocarps. The rhizogonean mosses ---including
Aulacomnium and Calomnion --- have a Gondwanan distribution centered
in Oceania, where most rhizogonean species have a substrate preference for tree ferns.
Altogether this suggests an origin of pleurocarps within Oceania from an epiphytic
ancestor during pre-Cretaceous time. The rhizogonean mosses should be given high
conservation priority because of their phylogenetic position and because they have
low species richness compared to pleurocarps.
Key words: Aulacomnium, pleurocarpous mosses, Rhizogoniaceae