A QUT-led study has found how increasing aridity and habitat variation and the subsequent emergence of grasslands shaped the evolution of modern kangaroos and wallabies.
- Modern kangaroos did not evolve immediately after the rainforest contracted
- The kangaroo family tree has had two major expansions in the past nine million years
- Only the wombats remain from the once dominant large herbivores whose extinction coincided with the rise of modern kangaroos and wallabies
The study, published in Molecular Phylogenetics and Evolution, resolves longstanding questions about when, and why, these iconic Australian marsupials diversified.
First author PhD researcher Clelia Gauthier, from QUT's School of Biology and Environmental Science, said the researchers found that the kangaroo family tree expanded in two major bursts over the past 9 million years.
"The first was during a late Miocene period of increasing dryness around 7-9 million years ago, and again in the Early Pliocene as grasslands began to emerge across the continent around 5-4.5 million years ago," Ms Gauthier said.
"Our research has generated the most comprehensive molecular evolutionary dataset to date by combining complete mitochondrial genomes with 11 nuclear genes across all living kangaroo and wallaby genera.
"By placing genetic evidence alongside Australia's fossil record, we could see that modern kangaroos didn't evolve immediately after rainforest contraction, as has often been thought.
"Instead, they diversified later, initially as Australia's habitats became drier and more varied, and then again as the expansion of grasses favoured the grazing and mixed feeding lineages we see today."
Professor Matthew Phillips said the findings clarified how environmental pressures reshaped the competitive landscape for marsupial herbivores.
"The rise of modern kangaroos and wallabies coincided with the extinction of many of the formerly dominant large herbivores from the group that now only includes wombats," Professor Phillips said.
"More arid and variable habitats likely shifted the balance of evolutionary competition in favour of kangaroos and wallabies, because travelling further for water and poorer quality forage increases the energetic benefits of their hopping and gut adaptations."
The study revealed:
- Macropodines (the group containing most modern kangaroos and wallabies) originated around 7-9 million years ago, as aridity and habitat variability increased.
- The second major diversification occurred around 5-4.5 million years ago, coinciding with the earliest emergence of incipient grasslands.
- The iconic "Macropus" group - including kangaroo, wallaroo, and wallaby species - rapidly diversified during this second period.
- Fossil evidence, including the earliest macropodine fossils from around eight million years ago, closely matches the molecular findings.
QUT researchers on the project include Clelia Gauthier, William G. Dodt, Manuela Cascini, Zachary K. Stewart, Professor Peter J. Prentis, and Professor Matthew Phillips, all from the School of Biology and Environmental Science, the Centre for Environment and Society and the Centre for Agriculture and the Bioeconomy, along with national and international collaborators:
The researchers are from QUT's School of Biology and Environmental Science and Centre for Agriculture and the Bioeconomy, working alongside colleagues from the Research Centre for Ecosystem Resilience at the Botanic Gardens of Sydney, the Senckenberg Biodiversity and Climate Research Centre in Frankfurt, from the South Australian Museum, The University of Adelaide, the Australian Museum Research Institute, Macquarie University, Flinders University, and the ARC Centre of Excellence for Australian Biodiversity and Heritage.
The study, Diversification of kangaroos and broader turnover among marsupial terrestrial herbivores coincided with emerging aridification then incipient grasslands was published in Molecular Phylogenetics and Evolution.
