The GABI in Southern South America

The Great American Biotic Interchange (GABI) between North and South America is one of the most important events in the history of land mammals. The interchange occurred in several phases during more than nine million years. We here analyze the chronology and dynamics of the GABI, the evolution of some South American mammalian groups through time, and the Quaternary mammalian extinctions. As the GABI was a complex process, we divide it into ProtoGABI and GABI 1 to 4. In our concept, the extinction of the megafauna by the gatherer/hunters that entered South American during the latest Pleistocene is a part of the GABI. The putative scarce frequency of extinct mammals in archeological sites is discussed. The evolutive relevance of the GABI is reflected in that half of the species living in South America had a North American ancestry. A final process, not included in the GABI, is the remarkable alteration of ecosystems by modern man. Presently, the composition and distribution of almost all autochthonous land mammal faunas are changing dramatically. Moreover, frequently they are replaced with domesticated and/or wild exotic species.