In biogeography, geodispersal is the erosion of barriers to gene flow and biological dispersal (Lieberman, 2005.; Albert and Crampton, 2010.). Geodispersal differs from vicariance as a means of explaining the patterns of distribution among related species. In geodispersal, the geographical ranges of individual taxa, or of whole biotas, are merged by erosion of a physical barrier to gene flow or dispersal.
A well documented example of geodispersal in between continental ecosystems was the Great American Biotic Interchange (GABI) between the terrestrial faunas and floras of North America and South America, that followed the formation of the Isthmus of Panama about 3 million years ago. Another well documented example of geodispersal was the formation of the modern Amazon River Basin about 10 million years ago, which involved the merging of previously isolated Neotropical fish faunas to form what is now the most species-rich continental aquatic ecosystem on Earth (Oberdorff et al., 2011).