title: Genetic and palaeo-climatic evidence for widespread persistence of the coastal tree species Eucalyptus gomphocephala (Myrtaceae) during the Last Glacial Maximum.
abstract: OBJECTIVE
  Few phylogeographic studies have been undertaken of species confined to narrow, linear coastal systems where past sea level and geomorphological changes may have had a profound effect on species population sizes and distributions. In this study, a phylogeographic analysis was conducted of Eucalyptus gomphocephala (tuart), a tree species restricted to a 400 × 10 km band of coastal sand-plain in south west Australia. Here, there is little known about the response of coastal vegetation to glacial/interglacial climate change, and a test was made as to whether this species was likely to have persisted widely through the Last Glacial Maximum (LGM), or conforms to a post-LGM dispersal model of recovery from few refugia.
  
  
  METHODS
  The genetic structure over the entire range of tuart was assessed using seven nuclear (21 populations; n = 595) and four chloroplast (24 populations; n = 238) microsatellite markers designed for eucalypt species. Correlative palaeodistribution modelling was also conducted based on five climatic variables, within two LGM models.
  
  
  RESULTS
  The chloroplast markers generated six haplotypes, which were strongly geographically structured (GST = 0·86 and RST = 0·75). Nuclear microsatellite diversity was high (overall mean HE 0·75) and uniformly distributed (FST = 0·05), with a strong pattern of isolation by distance (r(2) = 0·362, P = 0·001). Distribution models of E. gomphocephala during the LGM showed a wide distribution that extended at least 30 km westward from the current distribution to the palaeo-coastline.
  
  
  CONCLUSIONS
  The chloroplast and nuclear data suggest wide persistence of E. gomphocephala during the LGM. Palaeodistribution modelling supports the conclusions drawn from genetic data and indicates a widespread westward shift of E. gomphocephala onto the exposed continental shelf during the LGM. This study highlights the importance of the inclusion of complementary, non-genetic data (information on geomorphology and palaeoclimate) to interpret phylogeographic patterns.
authors.affiliation: Botanic Gardens and Parks Authority, Kings Park and Botanic Garden, West Perth, Western Australia 6005, Australia.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Nevill
authors.forename: Donna
authors.initials: D
authors.lastname: Bradbury
authors.forename: Anna
authors.initials: A
authors.lastname: Williams
authors.forename: Sean
authors.initials: S
authors.lastname: Tomlinson
authors.forename: Siegfried L
authors.initials: SL
authors.lastname: Krauss
mesh_terms: D002467:Cell Nucleus / Q000235:genetics; D002736:Chloroplasts / Q000235:genetics; D057231:Climate Change; D005052:Eucalyptus / Q000235:genetics*; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes / Q000235:genetics; D046448:Ice Cover; D018895:Microsatellite Repeats; D010163:Paleontology; D058974:Phylogeography; D013021:South Australia
keywords: Australian biogeography; Eucalyptus gomphocephala; LGM; Last Glacial Maximum; Myrtaceae; climate change; coastal geomorphology; founder effects; microsatellites; palaeodistribution modelling; phylogeography; south-western Australia; southern hemisphere; tuart