Biotic interchange

[3] The general cause of a biotic interchange is the disappearance of a barrier that had been previously blocking the dispersal of species from two distinct biotas.

[3][2] Many of the biotic interchanges studied have shown an asymmetry in the sharing of species between two biotas.

Fewer species travelled from the Mediterranean into the Red Sea (3 molluscs, 0 crabs, and 6 fish).

[1] There are many hypotheses that attempt to explain the asymmetry and general processes involved in biotic interchange: During the Trans-Arctic Interchange (3.5 million years ago, Early Pliocene) sea levels rose, submerging the Bering Strait, and allowing marine organisms from the North Pacific and North Atlantic/Arctic Ocean to come into contact with each other.

[3] During the Great American Interchange (3 million years ago, Pliocene) tectonic forces pushed North and South America together, allowing for the formation of the Panamanian land bridge linking the two continents together.

[3] The African and Eurasian Interchange (18 million years ago, early Miocene) occurred between Africa and Eurasia through the Middle East after the Tethys sea closed.

Highways are one example of a manmade dispersal barrier . [ 2 ]
This map shows the Bering land bridge that allowed for the hypothesized invasion of humans from Asia into North America. It also shows the reestablishment of the Bering Strait after the glaciation, allowing for the interchange of marine organisms between the Pacific and Arctic Oceans. [ 5 ] [ 4 ] [ 3 ]