Darwin was an early exponent of the importance of 'occasional means of dispersal' in accounting for the present-day distribution of plants and animals. This study examined the implications of capture on the water surface of meltwater and seawater for the local and long-range dispersal of Antarctic springtails. Individuals of the maritime Antarctic collembolan Cryptopygus antarcticus, were floated on tap water and seawater at 0, 5 and 10 1C. LT 50 s on seawater were 34 (10 1C), 65 (5 1C) and 75 (0 1C) days. On tap water, LT 50 s were 69 (10 1C), 126 (5 1C) and 239 (0 1C) days. Less than 20% escaped from the water surface. A significantly greater proportion of springtails moulted on tap water and viable offspring were produced on both tap water and seawater. Comparison across treatments of survival of moulting and non-moulting individuals found significantly greater survival in moulting animals for three of the treatment combinations. It is suggested that moult exuviae facilitate survival on the water film through the simultaneous provision of a flotation aid and a source of nourishment -that is, an 'edible raft'. A separate experiment measuring changes in haemolymph osmolality over time on tap water and seawater at 2 and 5 1C found significant differences in all treatments. Causes of mortality are discussed in relation to osmoregulatory failure and starvation.

Aerial dispersal has been frequently proposed as a potential mechanism by which polar terrestrial arthropods are transported to, and settle the ice free habitats of Antarctica, but to date there has been little substantive evidence in support of this hypothesis. Using water traps we investigated aerial deposition of arthropods on Lagoon Island, Ryder Bay, on the Antarctic Peninsula. Over a period of five weeks, trapping at three different altitudes, we captured a total of nine springtails, Cryptopygus antarcticus, all alive. This is the first study to demonstrate conclusively the survival of wind-borne native arthropods within Antarctica. By scaling the modest trapping area and success against island surface area, it is clear that hundreds, if not thousands, of springtails are regularly relocated by winds between the terrestrial habitats of Marguerite Bay. We use known desiccation rates of C. antarcticus and wind speeds to predict the likelihood of successful dispersal between the principal terrestrial habitats of the larger Marguerite Bay. Implications for local and long-range dispersal are discussed in relation to C. antarcticus and other polar arthropods.

Abstract:The mitochondrial COI gene of the Antarctic springtail, Gressittacantha terranova, was sequenced across a polar coastal landscape at Terra Nova Bay, northern Victoria Land. Samples from two altitudinal transects in the foothills directly south of Campbell Glacier were compared with samples from Springtail Valley (northern foothills) as an external reference population. We found that mtDNA haplotypes clustered into two lineages (clades) with a mean sequence divergence of 10% (uncorrected distance). However, there was no phylogeographic structure found at this spatial (landscape) scale with haplotypes from both divergent clades found sympatric across most populations. At the landscape scale, the considerable genetic divergence revealed within G. terranova is around five times greater than any other continental Antarctic springtail examined to date. These data indicate a Pliocene divergence event in G. terranova around 4-5 million years ago. The unusual distributional profile of haplotypes -occurrence of multiple haplotypes at single sites and genetic contiguity between sites that are not physically contiguoussuggests a subsequent 'reshuffling' of haplotypes in the Holocene that has an ecological basis.

1. Cold tolerance is a fundamental adaptation of insects to high latitudes. Flexibility in the cold hardening process, in turn, provides a useful indicator of the extent to which polar insects can respond to spatial and temporal variability in habitat temperature.2. A scaling approach was adopted to investigate flexibility in the cold tolerance of the high Arctic collembolan, Hypogastrura tullbergi , over different time-scales. The cold hardiness of animals was compared from diurnal warming and cooling phases in the field, and controlled acclimation and cooling treatments in the laboratory. Plasticity in acclimation responses was examined using three parameters: low temperature survival, cold shock survival, and supercooling points (SCPs).3. Over time-scales of 24 -48 h, both field animals from warm diurnal phases and laboratory cultures from a 'warm' acclimation regime (18 °C) consistently showed greater or equivalent cold hardiness to animals from cool diurnal phases and acclimation regimes (3 °C).4. No significant evidence was found of low temperature acclimation after either hours or days of low temperature exposure. The cold hardiness of H. tullbergi remained 'seasonal' in character and mortality throughout was indicative of the summer state of acclimatization.5. These data suggest that H. tullbergi employs an 'all or nothing' cryoprotective strategy, cold hardening at seasonal but not diel-temporal scales.6. It is hypothesised that rapid cold hardening offers little advantage to these high Arctic arthropods because sub-zero habitat temperatures during the summer on West Spitsbergen are rare and behavioural migration into soil profiles offers sufficient buffering against low summer temperatures.