title: Proliferation of East Antarctic Adélie penguins in response to historical deglaciation.
abstract: BACKGROUND
  Major, long-term environmental changes are projected in the Southern Ocean and these are likely to have impacts for marine predators such as the Adélie penguin (Pygoscelis adeliae). Decadal monitoring studies have provided insight into the short-term environmental sensitivities of Adélie penguin populations, particularly to sea ice changes. However, given the long-term nature of projected climate change, it is also prudent to consider the responses of populations to environmental change over longer time scales. We investigated the population trajectory of Adélie penguins during the last glacial-interglacial transition to determine how the species was affected by climate warming over millennia. We focussed our study on East Antarctica, which is home to 30 % of the global population of Adélie penguins.
  
  
  METHODS
  Using mitochondrial DNA from extant colonies, we reconstructed the population trend of Adélie penguins in East Antarctica over the past 22,000 years using an extended Bayesian skyline plot method. To determine the relationship of East Antarctic Adélie penguins with populations elsewhere in Antarctica we constructed a phylogeny using mitochondrial DNA sequences.
  
  
  RESULTS
  We found that the Adélie penguin population expanded 135-fold from approximately 14,000 years ago. The population growth was coincident with deglaciation in East Antarctica and, therefore, an increase in ice-free ground suitable for Adélie penguin nesting. Our phylogenetic analysis indicated that East Antarctic Adélie penguins share a common ancestor with Adélie penguins from the Antarctic Peninsula and Scotia Arc, with an estimated age of 29,000 years ago, in the midst of the last glacial period. This finding suggests that extant colonies in East Antarctica, the Scotia Arc and the Antarctic Peninsula were founded from a single glacial refuge.
  
  
  CONCLUSIONS
  While changes in sea ice conditions are a critical driver of Adélie penguin population success over decadal and yearly timescales, deglaciation appears to have been the key driver of population change over millennia. This suggests that environmental drivers of population trends over thousands of years may differ to drivers over years or decades, highlighting the need to consider millennial-scale trends alongside contemporary data for the forecasting of species' abundance and distribution changes under future climate change scenarios.
authors.affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, 7001, TAS, Australia. Jane.Younger@utas.edu.au.|Australian School of Advanced Medicine, Macquarie University, 2 Technology Place, 2109, NSW, Sydney, Australia. Jane.Younger@utas.edu.au.
authors.forename: Jane
authors.initials: J
authors.lastname: Younger
authors.affiliation: Australian Antarctic Division, 203 Channel Highway, Kingston, 7050, TAS, Australia. Louise.Emmerson@aad.gov.au.
authors.forename: Louise
authors.initials: L
authors.lastname: Emmerson
authors.affiliation: Australian Antarctic Division, 203 Channel Highway, Kingston, 7050, TAS, Australia. Colin.Southwell@aad.gov.au.
authors.forename: Colin
authors.initials: C
authors.lastname: Southwell
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, 2 Technology Place, 2109, NSW, Sydney, Australia. Patrick.Lelliott@anu.edu.au.|John Curtin School of Medical Research, Australian National University, 131 Garran Road, Acton, 2601, ACT, Australia. Patrick.Lelliott@anu.edu.au.
authors.forename: Patrick
authors.initials: P
authors.lastname: Lelliott
authors.affiliation: Australian Institute of Marine Science, The UWA Oceans Institute, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia. K.Miller@aims.gov.au.|School of Biological Sciences, Private Bag 5, University of Tasmania, Hobart, 7001, TAS, Australia. K.Miller@aims.gov.au.
authors.forename: Karen
authors.initials: K
authors.lastname: Miller
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D001499:Bayes Theorem; D057231:Climate Change; D004272:DNA, Mitochondrial / Q000235:genetics; D046448:Ice Cover; D010802:Phylogeny; D046429:Spheniscidae / Q000235:genetics / Q000502:physiology*
chemical_list: D004272:DNA, Mitochondrial