Genetic variation and dispersal of Bryum argenteum and Hennediella heimii populations in the Garwood Valley, southern Victoria Land, Antarctica.

A detailed study was made of the extent of genetic variation within populat ions of two moss species, Bryum argenteum and Hennediella heimii, from the Garwood Valley in Southern Victoria Land, Antarctica. RAPD (Random Amplifie d Polymorphic DNA) technology was used to analyse over 30 clumps of each sp ecies, collected from adjacent sites in five small meltstream drainage chan nels. Overall, extensive genetic variation was found, with no two samples b eing identical in either species. For both species, most clumps showed with in-clump variation, although generally the shoots from each clump were most closely related to other shoots from that clump, indicating somatic mutati on. Of the B. argenteum isolates, most showed distinct clustering correspon ding to the five drainage channels, with some clustering within the top, mi ddle or bottom of the channels, and separation of northern and southern sid es of the valley. There was some evidence of across-channel dispersal for B . argenteum. For H. heimii, the situation was quite different; there was ve ry little clustering of clumps according to channel from which they were co llected. Rather, the isolates appeared to form one continuous population ac ross the five channels, with partial separation of northern and southern si des of the valley. These results are consistent with the predicted means of dispersal of these species in Antarctica: predominantly by water for B. ar genteum, and by wind for H. heimii.