Biology Reference
In-Depth Information
both interpreted this finding in the same way - biogeography reflects ancestry rather
than climate, because each species has evolved from other species at a particular
location, and then migrated outwards from the point of origin until a barrier was
reached.
The father of biogeography was Alfred Russel Wallace (1823-1919), whose co-
discovery of natural selection, you will recall, prompted Charles Darwin to publish
On the Origin of Species.
Wallace was the leading expert on the distribution of ani-
mal species in the nineteenth century, and worked in both the Amazon River basin
and the Malay Archipelago. He collected more than 125,000 specimens in the Malay
Archipelago, of which about 80,000 were beetles - I pointed out in the section on
biodiversity that most animals are insects, and that most insects are beetles. His
name is commemorated in the term “the Wallace line”, which describes the fact that
there is a clear separation of land species between the southeastern and northwestern
parts of Indonesia. The Wallace line is indicated in Fig. 4.22.
Fig. 4.22
The land animals and plants to the northwest of the Wallace line are very similar
to those found in other parts of Asia, but those to the southeastern side are more sim-
ilar to those found in Australia. This separation seems at first sight to be arbitrary,
but today we know from the geological evidence of past sea levels that the Wallace
line marks an ancient deep-water passage that separated the two land masses, even
when the sea levels were one hundred metres lower than they are today. This deep
