Alien microbes, fungi, plants and animals occur on most of the sub-Antarctic islands and some parts of the Antarctic continent. These have arrived over approximately the last two centuries, coincident with human activity in the region. Introduction routes have varied, but are largely associated with movement of people and cargo in connection with industrial, national scientific program and tourist operations. The large majority of aliens are European in origin. They have both direct and indirect impacts on the functioning of speciespoor Antarctic ecosystems, in particular including substantial loss of local biodiversity and changes to ecosystem processes. With rapid climate change occurring in some parts of Antarctica, elevated numbers of introductions and enhanced success of colonization by aliens are likely, with consequent increases in impacts on ecosystems. Mitigation measures that will substantially reduce the risk of introductions to Antarctica and the sub-Antarctic must focus on reducing propagule loads on humans, and their food, cargo, and transport vessels.

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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.

The 5'-terminal sequences of the virion protein mRNAs of ononis yellow mosaic and kennedya yellow mosaic tymoviruses were determined, and also the positions in the genomes of the transcription initiation sites of those mRNAs. Comparisons of the available genomic sequences of tymoviruses revealed two conserved regions, one at the initiation site and another longer sequence of sixteen nucleotides to the 5' side of it. The longer sequence, which we call the tymobox, was tested as a target for a designed ribozyme, which cleaved appropriate genomic fragments of three tymoviruses. A synthetic oligonucleotide with sequence complementary to the tymobox was shown to be a tymovirus-specific probe for diagnosing and identifying tymoviruses, except for wild cucumber mosaic tymovirus. The tymobox sequence was also used as a primer for the second strand DNA synthesis of dsDNA representing the virion protein gene of cacao yellow mosaic tymovirus, a tymovirus with unknown sequence. Thus, the tymobox is a useful tool in molecular studies of tymoviruses.

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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.

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