In investigating the extent of genetic diversity in Antarctic mosses the RAPD technique has proven especially useN in demonstrating that these mosses exhibit extensive genetic variation (levels being similar to those in temperate regions), and that within-colony variation is apparently caused not only by immigration and establishment of propagules from elsewhere, but also by mutagenesis. Dispersal of these mosses can also be followed using the RAPD technique; both short-distance dlspersal by wind or water (depending on the moss species) and longer distance dispersal by wind across the ice cap has been demonstrated. Relationships with temperate mosses of the same species are being investigated to determine the origins of Antarctic populations. Genetic technology is also facilitating the taxonomic identification of moss specimens which cannot be identified morphologically due to phenotypic plasticity in Antarctica. Together, these genetic studies are starting to provide information of fundamental scientific importance for understanding the evolution, origins and dispersal mechanisms of Antarctic mosses, and their response to climate change.

Mount Melbourne in northern Victoria Land, Antarctica, is a glaciated 2733 m volcanic cone. The moss Campylopuspyruormis occurs on two small areas of steam-warmed snow-free ground near its summit. This moss species also occurs in temperate regions world-wide, but has not been recorded elsewhere in continental Antarctica. RAPD (Random Amplified Polymorphic DNA) studtes of 26 samples of C. pyriformis from two areas of heated ground on Mount Melbourne showed there was genetic diversity within the population. Genetic evidence for dispersal between the two sites, together with some genetic variation within individual colonies, indicates a single colonisation event has probably occurred at this extremely isolated location followed by multiple mutations. A single sample of moss protonema was collected 25 years ago from steam-warmed ground near the summit of another volcano, Mount Erebus (3794 m), on Ross Island some 300 km south of Mount Melbourne. The moss could not be identified based on morphological and reproductive criteria, as all attempts to differentiate it to a recognisable gametophyte were unsuccessful. The RAPD technique has now shown it to be C. pyrlformis, and closely related to the population on Mount Melbourne.

No abstract

A detailed study was made of the extent of genetic variation within populations of two moss species, Bryum argenteum and Hennediella heimii, from the Garwood Valley in Southern Victoria Land, Antarctica. RAPD (Random Amplified Polymorphic DNA) technology was used to analyse over 30 clumps of each species, collected from adjacent sites in five small meltstream drainage channels. Overall, extensive genetic variation was found, with no two samples being identical in either species. For both species, most clumps showed within-clump variation, although generally the shoots from each clump were most closely related to other shoots from that clump, indicating somatic mutation. Of the B. argenteum isolates, most showed distinct clustering corresponding to the five drainage channels, with some clustering within the top, middle or bottom of the channels, and separation of northern and southern sides of the valley. There was some evidence of across-channel dispersal for B. argenteum. For H. heimii, the situation was quite different; there was very little clustering of clumps according to channel from which they were collected. Rather, the isolates appeared to form one continuous population across the five channels, with partial separation of northern and southern sides of the valley. These results are consistent with the predicted means of dispersal of these species in Antarctica: predominantly by water for B. argenteum, and by wind for H. heimii.

No abstract