The divergence of the subspecies recognised has been linked to isolation caused by aridity from climatic oscillations during the Pleistocene. It is thought that "G. p. plumifera" was originally present in the interior of Australia and much of north and central Australia in a less arid period. Subsequent aridity is thought to have resulted in the isolation of a western group, now recognised as "G. p". "ferruginea", followed by a later split of a northern group, currently recognised as "G. p. leucogaster". The later split thought to have resulted in less divergence.