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Biobuzz 6 - What's Been On - Paul Nevill's Oral Abstract

Phylogeography and refugia of disjunct populations of Eucalyptus regnans in south-eastern Australia


1 The School of Forest and Ecosystem Science, The University of Melbourne, and Cooperative Research Centre for Forestry, Water Street, Creswick, Victoria 3363, Australia

2 The School of Forest and Ecosystem Science, The University of Melbourne, and Cooperative Research Centre for Forestry, Parkville, Victoria 3010, Australia
Cyclical climate oscillations during the quaternary have had a strong influence on species distributions and evolution. During the Last Glacial Maximum (LGM), south-eastern Australia was colder and more arid than present day and tree species are thought to have contracted to coastal refugia. Chloroplast DNA has been used to examine the broad scale phylogeography of selected members of the Eucalyptus genus with studies focusing on the predominately lowland Eucalyptus globulus. Less is known about the effect of past climate changes on widespread montane species. This study examines the phylogeography of the south-east Australian montane tree species E. regnans and infers the location of refugia during past climate oscillations. Eucalyptus regnans is discontinuously distributed on the Australian mainland and on the large island of Tasmania. We determined the chloroplast DNA (cpDNA) haplotypes of 400 E. regnans individuals (40 locations) based on five chloroplast microsatellites. Among the 400 E. regnans individuals analysed 35 haplotypes were identified. Phylogenetic relationships were determined by maximum parsimony. Genetic structure was examined using an analysis of molecular variance (AMOVA) and a statistical parsimony network constructed showing the number of nucleotide differences between haplotypes. The statistical parsimony network and cladistic analysis show haplotypes divided into two distinct groups corresponding to continental Australia and Tasmania. The distribution of haplotypes across the range of E. regnans shows strong geographic patterns with many populations and even certain regions in which a particular haplotype is fixed. All samples from the central highlands of Victoria were fixed for one haplotype while all samples from the northern and central Tasmanian regions were fixed for other haplotypes. These regions are thought to have been treeless during the LGM. Many locations had unique haplotypes, particularly those in East Gippsland in Victoria, north-east Tasmania and south-east Tasmania. Higher haplotype diversity was found in putative refugia and lower haplotype diversity in areas likely to have been re colonized since the LGM. The data are consistent with the long term persistence of E. regnans in certain regions such as East Gippsland and the recent recolonisation of other regions, such as the central highlands of Victoria.

Key Words
chloroplast microsatellite, Eucalyptus, migration, pyhlogeography, refugia, south-eastern Australia