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Evolution

Bearing up well? Understanding the past, present and future of Australia's koalas

Black, KH, Price, GJ, Archer, M & Hand, SJ 2014, Gondwana Research, vol. 25, pp. 1186-1201.

Evidence from fossil records of the family Phascolarctidae indicates that these specialist folivores, of which the modern koala Phascolarctos cinereus is the last surviving member, are particularly sensitive to climate change. Knowledge about the nature and rate of change in previous palaeocommunities of phascolarctids together with data relating to the responses of modern koala populations to historic climatic extremes indicate that the future survival of the species is under threat.

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Family-level relationships among the Australasian marsupial ‘‘herbivores’’ (Diprotodontia: Koala, wombats, kangaroos and possums)

Phillips, MJ & Pratt, RC 2008, Molecular Phylogenetics and Evolution, vol. 46, pp. 594-605.

This study attempts to determine the phylogenetic relationships between families in Diprotodontia, a diverse order of marsupials occupying a range of niches across Australasia, including koalas, wombats, kangaroos and possums.  Using mitochondrial and nuclear sequences, phylogenetic analysis serves to resolve relationships that were previously inconclusive, specifically between Vombatiformes and Phalangerida groupings.

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Is the modern koala (Phascolarctos cinereus) a derived dwarf of a Pleistocene giant? Implications for testing megafauna extinction hypotheses

Price, GJ 2008, Quaternary Science Reviews, vol. 27, pp. 2516-2521. 

This study tested the hypothesis that the modern Australian koala (Phascolarctos cinereus) is a dwarf descendent of the extinct giant koala (Ph. stirtoni), which underwent body-size reduction during the Late Pleistocene-Holocene period. The implication of this hypothesis is that Ph. stirtoni survived the megafaunal extinction event of the Late Pleistocene, with Ph. cinereus being the evolutionary ‘end-point’. Findings suggest that the giant koala should be considered a species distinct from the modern koala.

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Molecular phylogenetics of the Diprotodontia (kangaroos, wombats, koala, possums, and allies)

Osborne, MJ, Christidis, L & Norman, JA 2002, Molecular Phylogenetics and Evolution, vol. 25, pp. 219-228.

The evolutionary relationships of diprotodontid order marsupials (kangaroos, wombats, koala, possums and others) were analysed using ND2 mitochondrial sequences. The findings were also compared with 12S ribosomal DNA (rDNA) sequences. Groupings of organisms descending from a common ancestor, or monophyly, were found for Burramyoidea, Phalangeroidea, Petauroidea, Tarsipedoidea, Macropodoidea and the Vombatiformes (wombats and koala) sub-orders and super-families. Discrepancies between genetic findings and current taxonomic ranks were found.

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The marsupial mitochondrial genome and the evolution of placental mammals

Janke, A, Feldmaier-Fuchs, G, Thomas, WK, von Haeseler, A & Pӓӓbo, S 1994, Genetics, vol. 137, no. 1, pp. 243-256.

The entire mitochondrial genome of the American opossum, Didelphis vinginiana, was sequenced here and its distinguishing features described. A phylogenetic tree was created from the genetic sequence which demonstrated that rodents formed an earlier mammalian branch than did primates. The rate of evolution of the mitochondrial genome is clocklike, and this knowledge combined with genetic data indicated that the mouse and rat diverged as long as 35 million years ago.

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