The Ethiopian Region is Africa south of the Sahara and the southern part of the
Arabian Peninsula. The large expanses of ocean along the coastlines and the
climatic barrier of the desert to the north have kept this realm isolated over long
geologic periods although the isolation is a relative descriptor since it is far from
complete. The region is tropical and subtropical so it has year-round warmth
and, at least, seasonally available water. The result is a region of great diversity.
Madagascar was a subregion on Wallace’s original map, but subsequent investiga-
tions have shown the island to be unique enough in its vertebrate population to be
accorded the status of a region.
The Oriental Region is composed of southern Asia and its associated islands
south of the Himalayas and the other mountain chains that delineate the northern
boundary of southern Asia. The Oriental Region is most similar to the Ethiopian
Region, being composed of tropical and subtropical climates. Yet, the Oriental
Region is usually thought of as being less diverse than the Ethiopian Region with
the exception of families of reptiles and birds.
The Australian Region is usually thought of as being “most unique.” There is not
extreme diversity because of the arid and semiarid nature of most of Australia, but
here can be seen a divergence in evolution from the other large landmasses of the
world. Australia started its break from Gondwanaland about 120 million years ago.
Animal life has taken its own course and, for instance, out of nine families of terres-
trial mammals there are eight endemic to Australia. Of note are the monotremes,
(egg laying) which are not found outside of the region, and the marsupials (the young
live in pouches), only a few of which are found outside of Australia. Modern work
has delineated the New Zealand Region as separate from Wallace’s Australian
Region, particularly because of the presence of many species of flightless birds.
Zoogeographic Regions 375Table 6. Terrestrial Zoographic Region as Delineated by Wallace
Zoogeographic region Number of animal families Number of endemic families
Neotropical 50 19
Nearctic 37 2
Palearctic 42 2
Ethiopian (including Madagascar) 52 18
Oriental 50 4
Australian (excluding New Zealand) 28 17