Great American Interchange

The Great American Interchange was an important zoogeographic event about three million years ago. Land and freshwater fauna migrated between North America and South America.^[1]

The migration happened during the Pliocene, 3.6–2.6 million years ago (mya). The volcanic Isthmus of Panama rose from the seafloor and bridged the two continents.

The land bridge in what is now Panama joined the Neotropic (roughly South America) and Nearctic (roughly North America) ecozones to form the Americas.

The interchange is visible from both stratigraphy and nature. Its most dramatic effect is on the distribution of mammals, but weak-flying or flightless birds, reptiles, amphibians, arthropods and even freshwater fish also migrated.

The differences in the fauna of North and South America had been known for some time. Both Humboldt and Darwin discussed it. The interchange as a concept was first fully laid out in 1876 by the "father of biogeography", Alfred Russel Wallace.^[2] Wallace had spent 1848–1852 exploring and collecting specimens in the Amazon Basin. Others who made significant contributions to understanding the event in the century that followed include Florentino Ameghino and George Gaylord Simpson.^[3]

Similar interchanges occurred earlier in the Cainozoic, when the former Gondwana continents of India and Africa made contact with Eurasia, about 50 and 30 mya respectively.^[4][5]

1. ↑ [The Great American Interchange is] "one of the most extraordinary events in the whole history of life". George Gaylord Simpson 1980. Splendid isolation: the curious history of South American mammals. Yale University Press, New Haven. 179
2. ↑ Wallace, Alfred Russel (1876). The geographical distribution of animals. New York: Harper and Brothers.
3. ↑ Marshall, L.G. (1988). "Land mammals and the Great American Interchange" (PDF). American Scientist. 76 (4). Sigma Xi: 380–388. Bibcode:1988AmSci..76..380M. Archived from the original (PDF) on 2013-03-02. Retrieved 2009-06-06.
4. ↑ Karanth, K. Praveen (2006). "Out-of-India Gondwanan origin of some tropical Asian biota" (PDF). Current Science. 90 (6). Indian Academy of Sciences: 789–792. Retrieved 2008-12-29.
5. ↑ Hedges, S. Blair (2001). "Afrotheria: plate tectonics meets genomics". PNAS. 98 (1). National Academy of Sciences: 1–2. doi:10.1073/pnas.98.1.1. PMC 33345. PMID 11136239.