Wallace line is area between Oriental and Australian regions
In letter written in 1858, Wallace expressed his view that the Indonesia Archipelago was inhabited by two distinct faunas, one found in the east, one in the west. The following year he defined these two regions, based on the distribution of birds, by placing the boundary between Lombok and Bali and between Borneo and Celebes. Hs struck that Borneo and Celebes should have suck different birds and yet be separated by no major physical or climatic barrier.
He believed that Borneo, along with Java and Sumatra had once been part of Asia, and that Timor, the Mollucas New Guinea and perhaps Celebes had once been part of a Pacific-Australian continents (Wallace, 1859). He insisted that on explanation of the origin of the fauna of Celebes would have to accept that there had been vast changes in the surface of the earth, a concept which challenged the established view but which we now know to be true. The line that Wallace drew east of the Phillipines through the Makassar Straits and Between Bali and Lombok (Wallace, 1863) came to be known as Wallace’s line. In 1910, three years before he died, Wallace decided that predominance of Asian forms on Celebes should be reflected in the line beingmoved east of Celebes (Wallace 1910).
Many other analyses have been performed on the distribution of animal species resulting in several different lines (Simpson, 1977). Weber’s line attempt to delimit the boundary of faunal balance, that is, where the ratio between Asian Australian animals is 50:50 (Weber 1904). Weber used mollusks and mammals in his analysis but he exact position of the line differs from one group of animals to another. For example, Asian reptiles and butterflies penetrate further east then do its birds and snails. Lydekker’s line delimits the western boundary of the strictly Australian fauna in much the same way as Wallace’s line delimits the eastern boundary of the Asian fauna; both these line effectively trace the 180-200 m depth contours around the Sahul and Sunda Continental shelves respectively.
The area between these two lines has been nominated as a separate region, subregion or transition area called Wallacea (Dickerson, 1928). This concept was first suggested by wallacea in 1863, but has been strongly criticized as the area does not comprise a homogenus fauna, and there is no gradual change in species composition across it; instead there are large number of endemic species (Stresemann, 1939; Simpson 1977). The name Wallcea should be retained, but describe the area between the oriental and Australian regions rather than as the name for a strict biogeographical entity.
BibliographyWhitten, A.J., Mustafa, M., &Henderson, G.S., 2002, The Ecology of Sulawesi, Periplus Publishing, Singapore
Wallacea, A. R. 1859. Letter from Mr. Wallace concerning the geographical distribution of birds
, 1863. On the physical geography of the malay Archipelago
, 1910. The world of life. London: Chapman and Hall
Simpson, G.G. 1977. Too many lines: the limits of the Oriental and Australian Zoogeographic regions.
Weber, M. 1904. Die saeugetiere einfuenrung in die anatomie und systematic der recenten und fossiflen mammalian
Dickersoon, R.E 1928. Distribution of life in the Philippines. Manila: Bureau st printing
Stresemann, E. 1939-1. die vogel von Celebes 1-3. J. Ornithol
Wallacea