What is Wallaces line?
The Wallace Line (or Wallace’s Line) is a boundary that separates the zoogeographical regions of Asia and Australasia. West of the line are found organisms related to Asiatic species; to the east, mostly organisms related to Australian species. The line is named after Alfred Russel Wallace, who noticed the apparent dividing line during his travels through the East Indies in the 19th century. The line runs through the Malay Archipelago, between Borneo and Sulawesi (Celebes); and between Bali (in the west) and Lombok (in the east). Evidence of the line was also noted in Antonio Pigafetta’s biological contrasts between the Philippines and the Spice Islands, recorded during the voyage of Ferdinand Magellan in 1521. The distance between Bali and Lombok is small, a matter of only about 35 kilometers. The distributions of many bird species observe the line, as many birds refuse to cross even the smallest stretches of open water. Many volant mammals (bats) have distributions that cross the Wal
Also known as “The Wallace Line,” this is an imaginary geographical feature trending the more or the less along the edge of the Sunda Shelf in Indonesia (in other words, tracing the dividing line between the shallow shelf waters to the west and deep ocean to the east). It extends from between the islands of Bali and Lombok (in the Lesser Sundas) on to between Borneo and Sulawesi, and from there continues northward to separate the Philippine island of Mindanao from the small islands of Sangir and Talaud that lie south of it. The significance of the line is that it identifies a major (though not entirely abrupt) faunal discontinuity: many major groups found to the west of the line do not extend east of it, and vice versa. It thus represents a kind of geologically/physiographically-influenced “front” of intermixture between two of the world’s main faunal realms, the Oriental and the Australian. See S53, S78, and S715 for Wallace’s fullest treatments of the subject, and secondary analysis
