| Summary: | The "silver" species Bryum subrotundifolium Jaeg. (Bryaceae) in Antarctica has undergone numerous taxonomic revisions. This research used the internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA (nrDNA) to estimate the phylogenetic relationships of silver Bryum specimens from Antarctica, the Subantarctic islands, New Zealand and Australia. Bryum subrotundifolium B. argenteum Hedw., B. capillare Hedw., and the non-silver species, B. pseudotriquetrum (Hedw.) Gaertn, Meyer et Scherb., which is also taxonomically difficult in Antarctica, were analysed with B. pseudotriquetrum used as an outgroup. Antarctic B. subrotundifolium formed a clade with the other B. subrotundfolium specimens and the B. argenteum specimens. This suggests that B. subrotundifolium is conspecific with B. argenteum. The Antarctic specimens formed a clade within the main B. argenteum!B. subrotundifolium clade. This combined with the variation in morphology observed in the Antarctic specimens suggest that the antarctic material is an ecotypical variant of B. argenteum. ITS sequence data indicated genetic homogeneity between geographically isolated populations of antarctic B. subrotundifolium contrary to evidence detected by random amplified polymorphic DNA analyses (RAPDs). Contamination was observed in the Antarctic moss specimens and multiple bands were detected in polymerase chain reaction (PCR) products from these specimens. The contaminating bands were found to be from a fungal species from the genus Phoma using a combination of molecular data and morphological examination. This provides a possible explanation for the high levels of variation detected using RAPDs and indicates the usefulness of universal DNA sequences with length polymorphisms, such as ITS sequences, for detecting contaminants in DNA samples for RAPD analysis. The development of microsatellite DNA markers in B. argenteum has commenced. This PCR-based technique is much less sensitive to contamination than RAPDs which use arbitrary primers to randomly amplify DNA throughout the genome. The primers used to amplify microsatellite DNA are targeted to a specific species and close relatives of it. Microsatellite DNA markers are expensive and time-consuming to develop. However, once developed they are far more reliable than RAPDs, require minimal amounts of DNA, are simple to use and can be used to detect variation at different levels within a population depending on the amount of polymorphism present in a locus. These markers will be employed in future population-level research of these cosmopolitan moss species in Antarctica and temperate regions.
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