Where Australia Collides with Asia The epic voyages of Joseph Banks, Charles Darwin, Alfred Russel Wallace and the origin

Where Australia Collides with Asia

of north-east Queensland. Asia’s green imperial pigeon has a gape and gullet which

is enormously extensible, allowing large nutmegs to be swallowed whole, and even

two or three can be accommodated in the crop at one time. The surrounding fruit is

quickly consumed and the seed passes through the digestive system, making these

pigeons perfect dispersal agents. The nutmeg of commerce is one tree that exists only

because imperial pigeons in Maluku love the oily mace surrounding the seed. These

birds spend the winter in Maluku and southern Papua New Guinea and the summer in

the rainforests of Northern Queensland.

Of the shared rainforest plants

botanists conclude that the eastward

migration of Asian flora into Papua

New Guinea has been more successful

as Asian species such as the dipterocarp

trees, which dominate the tropical Asian

rainforest, are found in New Guinea but

not in Australia. The westward migration

of Australian species that had already

adapted to an arid environment were less

successful at readapting to the tropics.

However, an exception might be the

clove tree (Myrtaceae, Syzygium) which

has eucalyptus shaped buds, as well as the

melaleuca trees growing on the islands of

Manipa and Buru which are clearly of an

Australian origin.

The area of Sulawesi and Maluku,

scientifically known as Wallacea, is a

curious melange of Asian continental

fragments, parts of the Indonesian

island arc system, and fragments of the

Australian continent moved westward by

the Pacific Plate. For example, the islands

of Ceram, Manipa and Buru are understood to be continental fragments broken off from

Australia. Some of these pieces have been shoved together to create strange hybrid

landforms such as the island of Sulawesi, of which the western half is considered to

be part of ancient Laurasia, the eastern half to be part of ancient Gondwanaland, and is

there also part of Africa? All of this caused Alfred Russel Wallace much consternation

as he tried to understand the unusual animal assemblage on this island.

The pied imperial or nutmeg pigeon

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