P. J. A. Pugh

Antarctic terrestrial life – challenging the history of the frozen continent?

Antarctica is a continent locked in ice, with almost 99.7% of current terrain covered by permanent ice and snow, and clear evidence that, as recently as the Last Glacial Maximum (LGM), ice sheets were both thicker and much more extensive than they are now. Ice sheet modelling of both the LGM and estimated previous ice maxima across the continent give broad support to the concept that most if not all currently ice‐free ground would have been overridden during previous glaciations. This has given rise to a widely held perception that all Mesozoic (pre‐glacial) terrestrial life of Antarctica was wiped out by successive and deepening glacial events. The implicit conclusion of such destruction is that most, possibly all, contemporary terrestrial life has colonised the continent during subsequent periods of glacial retreat. However, several recently emerged and complementary strands of biological and geological research cannot be reconciled comfortably with the current reconstruction of Antarctic glacial history, and therefore provide a fundamental challenge to the existing paradigms. Here, we summarise and synthesise evidence across these lines of research. The emerging fundamental insights corroborate substantial elements of the contemporary Antarctic terrestrial biota being continuously isolated in situ on a multi‐million year, even pre‐Gondwana break‐up timescale. This new and complex terrestrial Antarctic biogeography parallels recent work suggesting greater regionalisation and evolutionary isolation than previously suspected in the circum‐Antarctic marine fauna. These findings both require the adoption of a new biological paradigm within Antarctica and challenge current understanding of Antarctic glacial history. This has major implications for our understanding of the key role of Antarctica in the Earth System.

A synonymic catalogue of the Acari from Antarctica, the sub-Antarctic Islands and the Southern Ocean

The records, taxonomy and geographical distribution of 528 species of Acari collected from the Antarctic, sub-Antarctic islands and the Southern Ocean are collated. Included are free-living and phoretic mites, parasites and nidicoles associated with a variety of birds, seals and other introduced mammals, from terrestrial aquatic, seashore and benthic marine habitats. A number of these Acari have been introduced by humans, to and around research stations and disused whaling stations. A full alphabetical index to all current higher taxa, as well as current/redundant generic and specific names, is provided.

RESPONSE OF ANTARCTIC TERRESTRIAL MICROARTHROPODS TO LONG-TERM CLIMATE MANIPULATIONS

The terrestrial biota of the Antarctic Peninsula region are experiencing marked changes in climate, especially rising temperatures, precipitation, and UV-B radiation—a combination unique worldwide. These changes, combined with the inherent simplicity of terrestrial communities, have led to their use as “model systems” to predict the future climate change responses of biota at lower latitudes. However, studies integrating responses at different levels of the community trophic structure are lacking. We report here the consequences on the soil microarthropod community of a four-year, multivariate, climate-manipulation experiment carried out over vegetation near Palmer Station, Anvers Island, western Antarctic Peninsula. The experiment used a multifactorial randomized-block design, deploying filters to raise temperatures and reduce ultraviolet (UV)-B (280–320 nm) or both UV-B and UV-A (320–400 nm) radiation of existing vegetation, with further water and fertilizer amendment treatments. Seven microarthropod species recovered in sufficient numbers for statistical analyses showed considerable spatial aggregation independent of treatment, a feature typical of many soil invertebrates. Analyses using negative binomial generalized linear modeling identified further significant and consistent treatment impacts on both individual species and species groups. Relative to controls, manipulations increasing temperature decreased numbers of microarthropods (particularly Collembola), as did exposure to near-ambient levels of UV radiation (separate significant effects for both UV-A and UV-B), while water amendment increased numbers. The impacts of temperature and water are consistent with our understanding of the importance of these two environmental variables and their interaction in Antarctic terrestrial ecosystems. The negative impact of UV (-A or -B) on arthropod heterotroph and detritivore populations in the Antarctic terrestrial food web is likely to be a secondary consequence of UV impact on vegetation characteristics. This is, again, consistent with general predictions of the impact of changing UV climate on ecosystem function.

Biogeography of spiders (Araneae: Arachnida) on the islands of the Southern Ocean

The araneofauna of the extreme Southern Hemisphere is highly impoverished and disharmonic. Four dead anthropogenic immigrant spiders have been collected from Antarctica while only 115 verified species from 26 families are reported on the islands of the Southern Ocean. Cluster analysis of the verified Southern Ocean species distribution data identifies a weak, but distinct, Neotropical/South Atlantic association together with robust South Indian and South Pacific biogeographic clusters. These groupings, largely attributed to vicariance and/or endemism, contain little evidence of post-Pleistocene dispersal. Indeed the 14 records of anthropogenic origin suggest that the pace of recent human-mediated introduction has been at least 30 times more rapid than that of Holocene natural dispersal.The araneofauna of the extreme Southern Hemisphere is highly impoverished and disharmonic. Four dead anthropogenic immigrant spiders have been collected from Antarctica while only 115 verified species from 26 families are reported on the islands of the Southern Ocean. Cluster analysis of the verified Southern Ocean species distribution data identifies a weak, but distinct, Neotropical/South Atlantic association together with robust South Indian and South Pacific biogeographic clusters. These groupings, largely attributed to vicariance and/or endemism, contain little evidence of post-Pleistocene dispersal. Indeed the 14 records of anthropogenic origin suggest that the pace of recent human-mediated introduction has been at least 30 times more rapid than that of Holocene natural dispersal.

The origin of Arctic terrestrial and freshwater tardigrades

Abstract The tardigrade faunas of six Arctic sites (Canadian Axel Heiberg I., east and west coasts of Greenland, Iceland, Svalbard, Novaya Zemlya and the Russian Taimyr Peninsula) form, with those of northern North America, a coherent “Nearctic-Arctic” biogeographic cluster. This cluster is distinct from that of “Northern and Alpine Europe”. Few, if any, Arctic tardigrades survived Pleistocene glaciation in situ amongst ice-free refugia. Similarly, few/none moved south ahead of the advancing ice-cap into the deglaciated Palaearctic and Nearctic and subsequently returned north during the Holocene deglaciation. It is more probable that most Arctic tardigrades are derived from wind-blown Nearctic propagules that colonized the region during the Holocene.

A fungal pathogen in time and space: the population dynamics of Beauveria bassiana in a conifer forest.

The fungal entomopathogen Beauveria bassiana is ubiquitous in below-ground systems; however, there is a dearth of information on the above-ground diversity, temporal and spatial distribution of this fungus. Therefore, we assessed its occurrence in a conifer forest (Pseudotsuga monziesii and Pinus nigra var. maritima) using selective media to isolate B. bassiana from soil, branch and bark samples collected in October 2005, March and June 2006. Fungal density was the highest at all locations in October, declining in March and June, and absent from conifer branches in June. This above-ground decline most likely resulted from more extreme environmental conditions compared with those below ground. Molecular analyses (ISSR-PCR) indicated that B. bassiana is genetically diverse, comprising both distinct microhabitat-specific and seasonal isolates. The occurrence of dissimilar above- and below-ground isolates suggests that B. bassiana occupies various overlapping niches in these systems.

Biodiversity and biogeography of non-marine Mollusca on the islands of the Southern Ocean

There are no terrestrial and freshwater molluscs associated with Continental nor Maritime Antarctica. The malacofaunas of the cool-temperate and sub-Antarctic islands of the Southern Ocean are extremely depauperate, comprising a mere 68 site-records of 51 species from 27 genera in 13 families. The South Atlantic records are confined to the Falkland Islands, which harbour nine species (one bivalve, five pond snails and three terrestrial aliens), and South Georgia, where there is one Notodiscus sp. (Charopidae). The fauna of the South Indian Ocean islands of Prince Edward, Crozet, Kerguelen and Heard, comprises two alien slugs and endemic Notodiscus hookeri (Charopidae). The majority of species occur on the South Pacific Ocean Islands of Macquarie, Campbell, Auckland, Snares, Antipodes, Bounty and Chatham to the south and east of New Zealand. The Chatham fauna is dissimilar to that on the other South Pacific Islands, though both represent vicariant remnants of common South Pacific Is./New Zealand Athoracophoridae, Charopidae and Punctidae. There is, other than the broad South Indian Ocean distribution of Notodiscus hookeri, little evidence of Holocene dispersal and colonization. Indeed the Southern Ocean is an effective barrier and the different regional (South Atlantic/Indian/Pacific) faunas are principally vicariant and derived from local survivors of Pleistocene glaciation.

The terrestrial micro-arthropod fauna of the South Sandwich Islands

The South Sandwich Islands are an isolated maritime Antarctic volcanic island arc 550-600km south-east of South Georgia. The terrestrial biology of the islands, with emphasis on the unique habitats associated with volcanically warmed ground, was investigated in 1997 and compared with the data collected during the only previous (1964) terrestrial expedition to the archipelago. The terrestrial fauna includes 29 free-living micro-arthropod species (nine Collembola and 20 Acari) and two, currently unidentified, enchytraeid worms; a further eight parasitic and sublittoral Acari are recorded in the literature. Freshwater habitats are very restricted in the archipelago and no freshwater fauna was located. Supralittoral pools on a single island contained the marine isopod Cassidinopsis maculata. There are no endemic taxa and no shoreline invertebrates other than the supralittoral Archisotoma brucei (Collembola) and two Enchytraeidae. Diversity on individual islands is, in part, a function of available ice-free ground area. The majority of dominant species throughout the archipelago, Cryptopygus antarcticus (Collembola), Nanorchestes nivalis, Eupodes minutus, Alaskozetes antarcticus and Halozetes belgicae (Acarina), originate on other maritime Antarctic islands, while Ayersacarus tilbrooki (Acarina) is sub-Antarctic. Few (one to three) individuals of several other sub-Antarctic species were recorded by either 1964 or 1997 expeditions, but only Pilellus rykei (Acarina) was reported by both. None of the sub-Antarctic species thought to be associated with geothermally warmed ground in 1964 was confirmed in 1997, despite extensive sampling of the same sites. It is more probable that sub-Antarctic colonists frequently arrive on the South Sandwich Islands but are unable to establish longterm viable populations. Cryptopygus caecus, now widespread on Candlemas I., is a solitary exception to this generalization.

New records of Acari from the sub-Antarctic Prince Edward Islands

Abstract Sixty species of Acari are recorded from the sub-Antarctic Marion and Prince Edward Islands (the Prince Edward archipelago). Twenty of the 45 species collected on recent expeditions are new and currently undescribed. Other new taxa include a family of Mesostigmata, four new genera, and the first sub-Antarctic records of Cillibidae (Mesostigmata) and Eryngiopus (Prostigmata). Fifteen of the 31 species previously reported from the islands are confirmed, although eight of the previous accounts remain doubtful. The fauna, which shows a distinction between the shoreline and terrestrial components, comprises endemic, South Indian Ocean Province and sub-Antarctic mite species.

Acarine colonisation of Antarctica and the islands of the Southern Ocean: the role of zoohoria

A quarter of the terrestrial Acari recorded from Antarctica and the sub-Antarctic islands are parasitic haematophages or non-feeding phoretics associated with other larger and more mobile animals, especially sea birds and pterygote insects. Although flying sea birds are effective vectors of zoohoric mites into the region, penguins are not and merely serve as reservoir hosts. Similarly, most of the mites associated with insects were accidentally introduced by man as free-living adults that subsequently utilised a range of alien and indigenous insects as local dispersal mechanisms.