Z

Zoogeographic Regions

Traveling aboutEarth, it is manifest, even to the most casual of observers, that

animal life has significant differences atscalesof continents and large parts of

continents. The concept of zoogeographicregionsis 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 tax-

onomical hierarchy within the animalkingdom 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. Theboundariesare dependent on major

climateboundaries and/or distances overoceans. 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 “co-

founders” 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 sim-

ilar 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.

In his great 1876 work,The Geographic Distribution of Animals, Wallace iden-

tified six zoogeographic regions and component subregions for Earth. The region-

alization was made from vertebrate animals with little else considered. Additional

regions and boundary adjustments have been proposed by subsequent scholars, but

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