Triquetrella mxinwana, a new moss species from South Africa, with a phylogenetic and biogeographic hypothesis for the genus

We describe Triquetrella mxinwana, a new species presently known only from the winter rainfall area of South Africa. Within this region it is common in karroo and renosterveld, but it also occurs in fynbos. It differs from other Triquetrella species in the several low, bifid, papillae on each laminal cell, but is similar to the Australian Leptodontium paradoxum, differing in size and anatomical details. Although sporophytes of L. paradoxum are unknown, those of T. mxinwana have the peristome of Triquetrella rather than Leptodontium. Phylogenetic analysis of data from three chloroplast (rps4, trnL-F and psbA-trnH) and one nuclear (ITS1) loci confirms that T. mxinwana and L. paradoxum are sister taxa and together are sister to the rest of Triquetrella. This placement also better reflects gametophyte morphology, which, though intermediate between Triquetrella and Leptodontium, better fits the former. Divergence levels among species of Triquetrella are very low and molecular clock approaches indicate that all divergences are of Pliocene–Pleistocene age. The estimated time of the split between T. mxinwana and its nearest relative is concordant with independent paleoclimatic estimates of the time of onset of winter rainfall conditions in the Cape. The disjunctive distribution of the genus in areas of Mediterranean climate is attributed to dispersal rather than ancient vicariance.