the great american interchange of species (an introduction to biogeography )

The Great American Interchange of Species

(An Introduction to Biogeography)

Biogeography

• The branch of biology that deals with the geographical distribution of plants and animals.

• The father of biogeography is one Alfred Russell Wallace – also a forgotten father of evolution via natural selection with Darwin. – Before going to Indonesia, Wallace spent 1848 to

1852 exploring and collecting specimens in the Amazon basin.

When North Met South

• The land bridge between the Isthmus of Panama is recent in geologic history.

• It is volcanic in origin and made its appearance about 3 million years ago.

• Its appearance led to one of the great exchanges of flora and fauna seen to date. – North American species moved to South America

and vice versa (though North Am. Species got the better of it).

The Isthmus of Tehuantepec

• A lot of the species that migrate ended up going extinct while others, finding empty habitats, quickly went through speciation. Examples: an ancestral camel and fox.

Example: the Camelids

• Camels evolved on the plains of North America – they did not migrate to South America until the Isthmus of Panama emerged 3 million years ago.

• The ancestor to the South American camelids is megacamelus.

• As megacamelus moved south, speciation took place and gave rise to new species.

Some of those species appeared and went extinct. This is Macrauchenia, an extinct South American camel.

Example: the Camelids

• There are currently two wild living species of camel in South America.– The Guanaco– and the vicuña

Example: the Camelids

• The vicuña lives at high altitudes, 10,000 feet, on the altiplano the guanaco spread out at lower elevations in the Andes and all of the Patagonia.

• While the guanaco and vicuña were thriving in the Andes and Patagonia, the North American camels were exterminated by the arrival of human hunters to North America.

Example: Invaders from the South

• South America is less known for its marsupials but outside of Australia, it is the continent where they are most prevalent.

While most South American marsupials went extinct do to the arrival of North America’s placental mammal invaders (outcompeted by them), opossums , however, moved north when the Isthmus formed.

Faces of Opossums

Ours