Contrasting phylogeographical patterns for springtails reflect different evolutionary histories between the Antarctic Peninsula and continental Antarctica

We examined the genetic structure among populations and regions for thespringtails Cryptopygus antarcticus antarcticus and Gomphiocephalus hodgsoni(Collembola) to identify potential historical refugia and subsequent colonizationroutes, and to examine population growth/expansion and relative ages ofpopulation divergence.Location Antarctic Peninsula for C. a. antarcticus; Antarctic continent (southernVictoria Land) for G. hodgsoni.Methods Samples were collected from 24 and 28 locations across the AntarcticPeninsula and southern Victoria Land regions for C. a. antarcticus andG. hodgsoni, respectively. We used population genetic, demographic and nestedclade analyses based on mitochondrial DNA (cytochrome c oxidase subunit I andsubunit II).Results Both species were found to have population structures compatiblewith the presence of historical glacial refugia on Pleistocene (2 Ma–present) timescales,followed by post-glacial expansion generating contemporary geographicallyisolated populations. However, G. hodgsoni populations were characterized by afragmented pattern with several ‘phylogroups’ (likely ancestral haplotypes presentin high frequency) retaining strong ancestral linkages among present-daypopulations. Conversely, C. a. antarcticus had an excess of rare haplotypes witha much reduced volume of ancestral lineages, possibly indicating historicalfounder/bottleneck events and widespread expansion.Main conclusions We infer that these differences reflect distinct evolutionaryhistories in each locality despite the resident species having similar life-historycharacteristics. We suggest that this has predominantly been influenced byvariation in the success of colonization events as a result of intrinsic historicalglaciological differences between the Antarctic Peninsula and continentalAntarctic environments