Population genetics of three sympatric springtail species (Hexapoda: Collembola) from the South Shetland Islands: Evidence for a common biogeographic pattern

Three sympatric springtail species, from the South Shetland Islands archipelago in the maritime Antarctic, are analysed here in a common biogeographic and evolutionary framework. This study was designed to compare their population genetic structure using the same molecular marker. Haplotype data for the mitochondrial cox1 gene have been obtained for seven populations of Folsomotoma octooculata and are compared with the data obtained, in previous studies and the current one, for the sympatric species Cryptopygus antarcticus antarcticus, and Friesea grisea. Molecular data obtained are consistent with the hypothesis that all species have been present in the archipelago since well before the last glacial maximum (around 20 000 ybp) and that their early diversifications appear to be linked with known interglacial periods in the region. These springtails may have survived the last glacial cycle in local refugia, from which they dispersed subsequently to ice-free ground re-exposed during the current interglacial period. The populations of the different species diversified at different times, although all of them are within the Pleistocene epoch. We propose that the earliest diversification of haplotypes in all three springtails in this archipelago occurred from local refugia in Livingston I., with subsequent spread of some haplotypes throughout the South Shetland Islands.