Understanding how rosellas have evolved
There are three main colour varieties of the crimson rosella – crimson, yellow and orange – which are considered the same species, having evolved from a common ancestor.
They are some of the most variably coloured birds in Australia and occur throughout south-eastern Australia.
A 'ring theory' was previously suggested to explain their origin, where a species spreads to new areas and eventually joins back up with the populations where it started, forming a ring.
By that time, the populations at the join in the ring, may behave towards each other as two distinct species and might be unable to interbreed despite continuous gene flow or interbreeding between populations around the ring.
Investigating genetic relationships
With a team of researchers from Deakin University and the South Australian Museum, we investigated the genetic and geographical relationships between different populations of crimson rosellas and the possible reasons why they occur today where they do.
We found that in the case of the crimson rosellas, their separate genetic groups and differently coloured populations don't show simple links to geographical distributions of the colour forms.
For example, orange Adelaide and crimson Kangaroo Island rosellas are separated by 15 kilometres of ocean but are genetically similar. Conversely, genetic dissimilarity was found in the geographically linked yellow and orange populations of inland south eastern Australia.
We can reject the ring theory in its original form as it predicts that only one region of genetic dissimilarity should occur at the geographical location of the supposed join in the ring.
Providing clues to help manage biodiversity
This research suggests that the evolution of the crimson rosella's colour forms may not be due to the 'ring theory' as first thought.
Wildlife genetic research of this kind is increasing our understanding of the biogeography and evolution of Australia's land animals.
It is a piece in the puzzle of how we can sustainably manage Australia's biodiversity and ecosystem functions in the face of land use and a changing climate.