Patterns of population genetic structure for springtails and mites in southern Victoria Land, Antarctica Angela McGaughran a,b, * , Ian D. Hogg a , Mark I. Stevens b,c a Centre for Biodiversity and Ecology Research, University of Waikato, Private Bag 3105, Hamilton, New Zealand b Allan Wilson Centre for Molecular Ecology & Evolution, Massey University, Private Bag 11-222, Palmerston North, New Zealand c School of Biological Sciences, Monash University, Clayton 3800, Vic., Australia Received 25 May 2007; revised 21 September 2007; accepted 5 October 2007 Available online 23 October 2007 Abstract We sequenced the mitochondrial (mt) DNA cytochrome c oxidase subunit I gene to examine comparative phylogeographic patterns for the springtail Gomphiocephalus hodgsoni and the mite Stereotydeus mollis throughout their ranges in southern Victoria Land, Ant- arctica. Our aim was to extend previous genetic work to encompass a large ice-free area in the Dry Valleys. In particular, we sought to determine if this new region harboured high levels of genetic diversity and if patterns of genetic structure were congruent across taxa. Phylogenetic and nested clade analyses for G. hodgsoni and S. mollis showed similar patterns of population sub-structuring among loca- tions and highlighted several potential refugia that may have existed during glacial maxima. We identified greater levels of genetic diver- gence in S. mollis and suggest that there is a nucleotide substitution (mutation) rate difference between S. mollis and G. hodgsoni, and/or that S. mollis has had a longer association with the Antarctic landscape. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Glacial refugia; Mitochondrial DNA; Stereotydeus mollis; Gomphiocephalus hodgsoni; Phylogeography 1. Introduction There are several processes that may influence contem- porary patterns of population genetic structure (e.g. gene flow, genetic drift, fragmentation). In particular, repeated glacial cycles are likely to have had a marked influence on contemporary species’ ranges and population sizes through their effect on habitat and/or refugial availability (e.g. Knowles, 2001; Rowe et al., 2004). Such effects are likely to be particularly strong in Antarctica, where the local fauna has been exposed to a climate of increasing severity (including more than ten glacial cycles over the last million years (Hays et al., 1976)) since its isolation in the southern ocean following the break-up of Gondwana. The continent has been covered in a permanent ice sheet for 34 My, and the variable extent of this sheet over time has likely resulted in repeated shifts of species distributions in both the land and marine realms of the Antarctic (Rog- ers, 2006). It is well documented that several Antarctic locations have remained ice-free throughout the Last Glacial Maxi- mum (e.g. coastal areas, Burgess et al., 1994; Gore et al., 2001; Hodgson et al., 2001; lakes, Cromer et al., 2006). In addition, continental regions including Dronning Maud Land (Marshall and Pugh, 1996), the Prince Charles Mountains (Fink et al., 2000), the Antarctic Peninsula (Pugh and Convey, 2000), southern Victoria Land (Stevens and Hogg, 2003, 2006) and the Ellsworth Mountains (Con- vey and McInnes, 2005) have had ice-free areas for millions of years which are likely to have enabled long-term survival of terrestrial taxa in refugia (Cromer et al., 2006; Convey 1055-7903/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2007.10.003 * Corresponding author. Address: Allan Wilson Centre for Molecular Ecology & Evolution, Massey University, Private Bag 11-222, Palmerston North, New Zealand. Fax: +64 6 350 5626. E-mail address: a.mcgaughran@massey.ac.nz (A. McGaughran). www.elsevier.com/locate/ympev Available online at www.sciencedirect.com Molecular Phylogenetics and Evolution 46 (2008) 606–618