WALLACE'S LINE

hypothetical boundary between the Oriental and Australasian faunal regions, proposed by the 19th-century British naturalist Alfred Russel Wallace. The line extends from the Indian Ocean through the Lombok Strait (between the islands of Bali and Lombok), northward through the Makasar Strait (between Borneo and the Celebes), and eastward, south of Mindanao, into the Philippine Sea. Although many zoogeographers no longer consider Wallace's Line a regional boundary, it does represent an abrupt limit of distribution for many major animal groups. Many fish, bird, and mammal groups are abundantly represented on one side of Wallace's Line, but poorly or not at all on the other side. See also Weber's Line.