[5] Mathews described two additional subspecies of mulga parrot in 1912: P. varius rosinae, from a specimen collected from Yorke Peninsula, noting that it had less red on the abdomen and its upper breast was a darker green, and P. varius exsul from a specimen from Mount Magnet in Western Australia, reporting it had a more blue than green color overall, particularly on the cheeks.

[6] In 1917, he revised his classification, noting that he had assumed the type collection came from New South Wales but was now made aware that Brown's original specimen came from the Eyre Peninsula on the Spencer Gulf.

[9] A 2018 genetic analysis of specimens across the mulga parrot's range found that there were two lineages that had diverged around 402,000 years ago and recently expanded.

Preliminary investigation into physical characteristics that might distinguish them suggested that the red patch on the abdomen was possibly brighter and more extensive in the eastern population.

McElroy and colleagues agreed the two populations were distinct enough to be recognised as subspecies, however it is unclear to which group the type specimen belongs to.

[12] A 2015 study of museum specimens found that the bill surface area of male mulga parrots had increased by 10.7% between 1871 and 2008.

[15][12][16] The species ranges across the drier interior of the Australian continent, from Western New South Wales from Collarenebri, West Wyalong and Griffith westwards through the northwestern tip of Victoria and across South Australia and into the drier central regions of Western Australia west to the Wheatbelt and north to the Pilbara.