Incongruence among morphological species circumscriptions and two molecular datasets in Sarmentypnum (Bryophyta: Calliergonaceae)

Abstract

AbstractRelationships among species in Sarmentypnum, and Warnstorfia, are investigated based on the nuclear ITS and the chloroplast markers trnL–trnF, rpl16, and tRNA–Gly of up to 237 specimens. Six specimens in which morphology agrees with ITS sequences have chloroplast markers belonging to other species, whereas in two specimens morphology agrees with the chloroplast markers but have ITS sequences belonging to other species. Although hybridization has been recorded in Sarmentypnum, such incongruence could also be a result of other processes, including rapid morphological differentiation and incomplete lineage sorting. ITS and the chloroplast markers partly agree with the morphological species, although some of the latter appear to be polyphyletic or paraphyletic. Sarmentypnum exannulatum consists of two to three haplotype groups that are connected to S. sarmentosum, but not with each other. Sarmentypnum sarmentosum haplotypes are connected with haplotypes of most other species and may have played a central role in the genus' diversification. The trnL–trnF spacer inversion shows patterns congruent with other chloroplast information; it is therefore clearly informative. The incongruence among mainly non–coding molecular datasets and partial disagreement with morphological species could possibly be attributable to the special history of the boreal to arctic environments where Sarmentypnum is predominantly found. The species must be young in terms of number of generations and have experienced large–scale climatic oscillations during the Pleistocene. Incomplete lineage sorting in combination with rapid morphological evolution that is not reflected in the non–coding markers and an unknown frequency of hybridization most likely explains the observed incongruence.