The Wallace Line
Another Naturalist, Weber was interested in how far Australian animals and plants spread into the Eurasian area. He noticed that he could draw a line between Sulawesi and Irian Jaya (= Indonesian part of Papua New Guinea) and between Timor and Australia. To the west, the fauna is more than 50 percent Oriental, while to the east of the line, fauna is more than 50 percent Australian in origin.
Today biogeographers think of the area between these lines more as a zone of transition. This zone, encapsulating Sulawesi, Nusa Tenggara and Maluku, is called Wallacea. With animals and plants from both regions to draw upon, as well as a huge number of endemic species (= restricted to a particular geographic region and found nowhere else in the world), Wallacea is specially interesting for naturalists and divers alike.
Wallacea during the ice age
Dark green = dry land connecting the islands.