Phylogeographic differentiation in the mitochondrial control region in thekoala, Phascolarctos cinereus (Goldfuss 1817)

The koala, Phascolarctos cinereus, is a geographically widespread species e ndemic to Australia, with three currently recognized subspecies: P.c. adust us, P.c. cinereus, and P.c. victor. Intraspecific variation in the mitochon drial DNA (mtDNA) control region was examined in over 200 animals from 16 r epresentative populations throughout the species' range. Eighteen different haplotypes were defined in the approximate to 860 bp mtDNA control region as determined by heteroduplex analysis/temperature gradient gel electrophor esis (HDA/TGGE). Any single population typically possessed only one or two haplotypes yielding an average within-population haplotypic diversity of 0. 180 +/- 0.003, and nucleotide diversity of 0.16%. Overall, mtDNA control re gion sequence diversity between populations averaged 0.67%, and ranged from 0% to 1.56%. Nucleotide divergence between populations averaged 0.51%, and ranged from 0% to 1.53%. Neighbour-joining methods revealed limited phylog enetic distinction between geographically distant populations of koalas, an d tentative support for a single evolutionarily significant unit (ESU). Thi s is consistent with previous suggestions that the morphological difference s formalized by subspecific taxonomy may be interpreted as clinal variation . Significant differentiation in mtDNA-haplotype frequencies between locali ties suggested that little gene now currently exists among populations. Whe n combined with microsatellite analysis, which has revealed substantial dif ferentiation among koala populations, we conclude that the appropriate shor t-term management unit (MU) for koalas is the local population.