Molecular and morphological incongruence among the genera around Sarmentypnum (Bryophyta: Calliergonaceae)
Incongruence among molecular and morphological data for species and genus delineation has been shown to occur in several mosses. Based on the nuclear ITS 1 and 2, and the chloroplast trnL-trnF, rpl16, and tRNA-Gly, it is shown that such incongruence is relatively frequent in the genera Loeskypnum, Sarmentypnum, Straminergon, and Warnstofria. Using Neighbor joining, Jacknifing, and NeighborNet to evaluate relationships, ITS placed 3% of the morphologically identified specimens in an incorrect species and 1.5% in the wrong genus, and for the combined chloroplast data the corresponding figures were 3.5% and 1.5%. A combination of factors likely explains why some specimens are incorrectly placed by molecular data, including incomplete lineage sorting, rapid morphological differentiation, and transfer of genetic material between morphologically defined species. An arctic North American specimen of Straminergon stramineum with acuminate leaves was placed among Loeskypnum badium by chloroplast data, but not by ITS. This shows that also morphological data may be unstable and suggests that the acuminate leaf apex could be a result of hybridization between S. stramineum and L. badium. Even if a few percent of specimens will be incorrectly identified by the studied markers, identification work with barcodes will probably yield a higher frequency of correct identifications, at a lower cost, than employment of non-specialists for identification by morphology.