Australia: The Land Where Time Began

A biography of the Australian continent 

Australian Rodents

The northern invaders

As the leading edge of the Australian Plate, with New Guinea on its margin, approached southeast Asia, some rodents managed to reach Australia, sometime around 4 Ma. All the Australian rodents belong to the Murinae subfamily of the rodent family Muridae, including rats and mice. All of the specialised, distinctive Australian murines, and most of the rest of the Australian species, belong to the conilurine group, all descended from a single lineage that entered Australia (Breed &n Ford, 2006). At the time the rodents reached Australia much of the northern parts of Australia was covered by dry-country environments with no seed-eating marsupial fauna. It was an unoccupied niche to which rodents were supremely suited, the explosive radiation that followed their arrival resulted in 49 known species, covering a wide rage of morphologies, as the rodents rapidly adapted to semi-arid and arid environments. Some examples of the species they evolved are stick-nest rats, tree-rats, rock rats, hopping mice and pseudomice. Of these, the conilurines are clearly recent arrivals in Australia,  Pseudomys and Conilurus occur in both Australia and New Guinea, the remainder of the conilurines are endemic to Australia. The conilurines have no close relatives in either New Guinea or Asia (Breed & Ford, 2006).

The remainder of the rodent fauna of Australia arrived more recently than the conilurines, being of genera that are more diverse in New Guinea than in Australia. Mosaic-tailed rats (Uromys and Melomys), occur mostly in rainforests, in New Guinea and northeastern Australia. What fossils there are indicated they probably migrated from New Guinea to Australia along a forest corridor that crossed the Carpentarian Plain, some time in the early Pleistocene. Some rats are more widely distributed across Australia, such as Hydromys and Xeromys, water rats, being found around the coast and along inland waterways. It is believed they may have entered Australia from coastal New Guinea, or along the rivers that flowed from New Guinea onto the Carpentarian Plain in the Early Pleistocene.

True rats (Rattus) also reached Australia, 2 species of which also occur in New Guinea, and also there are a larger number of species endemic to New Guinea. Forests and tropical savannas are the locations where these tend to be found. Through central Australia the Plague rat, R. villosissimus, is widely distributed. (Johnson, 2006).

 

Sources & Further reading

Chris Johnson, Australia's Mammal Extinctions, a 50,000 year history, Cambridge University Press, 2006

  

 

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Last updated 18/10/2010

 

 

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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading