Genetics and variations Edit
Traditionally, three distinct subspecies have been recognised: the Queensland koala (P. c. adustus, Thomas 1923), the New South Wales koala (P. c. cinereus, Goldfuss 1817), and the Victorian koala (P. c. victor, Troughton 1835). These forms are distinguished by pelage colour and thickness, body size, and skull shape. The Queensland koala is the smallest of the three, with shorter, silver fur and a shorter skull. The Victorian koala is the largest, with shaggier, brown fur and a wider skull.[20][21] The boundaries of these variations are based on state borders, and their status as subspecies is disputed. A 1999 genetic study suggests that the variations represent differentiated populations with limited gene flow between them, and that the three subspecies comprise a single evolutionarily significant unit.[21] Other studies have found that koala populations have high levels of inbreeding and low genetic variation.[22][23] Such low genetic diversity may have been a characteristic of koala populations since the late Pleistocene.[24] Rivers and roads have been shown to limit gene flow and contribute to the genetic differentiation of southeast Queensland populations.[25] In April 2013, scientists from the Australian Museum and Queensland University of Technology announced they had fully sequenced the koala genome.[26]