Changing environments and resource demands present challenges to Antarctic conservation.

Increasing numbers of scientific and tourist vessels are entering the Antarctic region and have the potential to bring with them a range of organisms that are not currently found in the region. Little is known about the frequency of such introductions or the identity and survivorship of the species associated with them. In this study, we report the findings of an inspection of the sea chests of the South African National Antarctic Programme supply vessel, the SA 'Agulhas', while the vessel was in dry dock in June 2006. Large populations of a known invasive mussel, Mytilus galloprovincialis (Lamarck), were found. By extrapolating from shell length, the age of individuals was estimated, the results of which suggest that some specimens have survived transportation to the Antarctic region on multiple occasions. These findings are cause for concern and demonstrate that Antarctic research and supply vessels are important vectors for marine non-indigenous species into the region.

It has long been maintained that the majority of terrestrial Antarctic species are relatively recent, post last glacial maximum, arrivals with perhaps a few microbial or protozoan taxa being substantially older. Recent studies have questioned this 'recolonization hypothesis', though the range of taxa examined has been limited. Here, we present the first large-scale study for mites, one of two dominant terrestrial arthropod groups in the region. Specifically, we provide a broad-scale molecular phylogeny of a biologically significant group of ameronothroid mites from across the maritime and sub-Antarctic regions. Applying different dating approaches, we show that divergences among the ameronothroid mite genera Podacarus, Alaskozetes and Halozetes significantly predate the Pleistocene and provide evidence of independent dispersals across the Antarctic Polar Front. Our data add to a growing body of evidence demonstrating that many taxa have survived glaciation of the Antarctic continent and the sub-Antarctic islands. Moreover, they also provide evidence of a relatively uncommon trend of dispersals from islands to continental mainlands. Within the ameronothroid mites, two distinct clades with specific habitat preferences (marine intertidal versus terrestrial/supralittoral) exist, supporting a model of within-habitat speciation rather than colonization from marine refugia to terrestrial habitats. The present results provide additional impetus for a search for terrestrial refugia in an area previously thought to have lacked ice-free ground during glacial maxima.

Over the past two decades seven non-indigenous vascular plant or arthropod species have established reproducing populations at sub-Antarctic Marion Island (46°54ЈS, 37°55ЈE). Here we record the eighth establishment, a braconid wasp Aphidius matricariae Haliday, which uses the aphid Rhopalosiphum padi (Linnaeus) as its only host on the island. Molecular markers (18S rDNA and mtCOI) support the conventional taxonomic identiWcation and indicate that all individuals are characterized by a single haplotype. Surveys around the island show that adult abundance and the frequency of aphid parasitism are highest at Macaroni Bay on the east coast, and decline away from this region to low or zero values elsewhere on the coast. The South African research and supply vessel, the SA Agulhas, regularly anchors at Macaroni Bay, and Aphidius sp. have been collected from its galley hold. Current abundance structure, low haplotype diversity, and the operating procedures of the SA Agulhas all suggest that the parasitoid was introduced to the island by humans. Regular surveys indicate that this introduction took place between April 2001 and April 2003, the latter being the Wrst month when this species was detected. The wasp's establishment has signiWcantly added to trophic complexity on the island. Low haplotype diversity suggests that propagule pressure is of little consequence for insect introductions. Rather, single or just a few individuals are probably suYcient for successful establishment.

Antarctic ecosystems are at risk from the introduction of invasive species. The first step in the process of invasion is the transportation of alien species to Antarctic in a viable state. However, the effect of longdistance human-mediated dispersal, over different timescales, on propagule viability is not well known. We assessed the viability of Poa trivialis seeds transported to Antarctica from the UK, South Africa and Australia by ship or by ship and aircraft. Following transportation to the Antarctic Treaty area, no reduction in seed viability was found, despite journey times lasting up to 284 days and seeds experiencing temperatures as low as -1.5°C. This work confirms that human-mediated transport may overcome the dispersal barrier for some propagules, and highlights the need for effective pre-departure biosecurity measures.