Zoogeographic Regions

Traveling about Earth, it is manifest, even to the most casual of observers, that animal life has significant differences at scales of continents and large parts of continents. The concept of zoogeographic regions is explanatory of the animal geography of the planet. Rather than being controlled by the plant environment, a zoogeographic region is a large area based on forms of animals (taxonomy) and the evolutionary connections (phylogenetic relations) between them. The taxonomical hierarchy within the animal kingdom ranges from general to specific: phyla, class, order, family, genus, and species. Zoogeographic regions are focused on the nature of vertebrate families and species unique to that region. Vertebrates are those animals possessing backbones surrounding their nerve chords and include families of mammals, birds, fish, amphibians, and reptiles. That is, this regionalization is based on a minority of the animals present on the planet.

Rather than being thought of as exactly defined, zoogeographic regions are composites of the totality of animal life. The boundaries are dependent on major climate boundaries and/or distances over oceans. Considering other concepts such as the great amounts of time over which these families of animals have evolved, long-term changes in Earth’s systems such as climate change and continental drift have played roles in the present day configuration of the zoogeographic regions.

Alfred Russel Wallace was, with Charles Darwin, one of the first two “cofounders” of the theory of evolution. Wallace was a naturalist and geographer and is the acknowledged scientific father of animal geography (zoogeography). In the 1850s he was on an expedition collecting animal specimens in the Malay Archipelago. He noticed that between the Malay islands and the nearby Celebes there was a significant divide in the taxonomy. To the west, the animals were similar to what was known in Asia and to the east the species more resembled those in Australia. This distinction was so marked over a few tens of kilometers that it became known as “Wallace’s Line.” This discovery inspired Wallace to study the rest of the world to identify major zoogeographic boundaries.