Biological evidence supports an early and complex emergence of the Isthmus of Panama.
The linking of North and South America by the Isthmus of Panama had major impacts on global climate, oceanic and atmospheric currents, and biodiversity, yet the timing of this critical event remains contentious. The Isthmus is traditionally understood to have fully closed by ca. 3.5 million years ago (Ma), and this date has been used as a benchmark for oceanographic, climatic, and evolutionary research, but recent evidence suggests a more complex geological formation. Here, we analyze both molecular and fossil data to evaluate the tempo of biotic exchange across the Americas in light of geological evidence. We demonstrate significant waves of dispersal of terrestrial organisms at approximately ca. 20 and 6 Ma and corresponding events separating marine organisms in the Atlantic and Pacific oceans at ca. 23 and 7 Ma. The direction of dispersal and their rates were symmetrical until the last ca. 6 Ma, when northern migration of South American lineages increased significantly. Variability among taxa in their timing of dispersal or vicariance across the Isthmus is not explained by the ecological factors tested in these analyses, including biome type, dispersal ability, and elevation preference. Migration was therefore not generally regulated by intrinsic traits but more likely reflects the presence of emergent terrain several millions of years earlier than commonly assumed. These results indicate that the dramatic biotic turnover associated with the Great American Biotic Interchange was a long and complex process that began as early as the Oligocene-Miocene transition.
Smithsonian Tropical Research Institute, 0843-03092 Balboa, Panamá; Department of Biological and Environmental Sciences, University of Gothenburg, SE-413 19 Gothenburg, Sweden; christinedbacon@gmail.com.
Christine D
CD
Bacon
Department of Biological and Environmental Sciences, University of Gothenburg, SE-413 19 Gothenburg, Sweden; Department of Ecology and Evolution, University of Lausanne and Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland;
Daniele
http://orcid.org/0000-0003-0100-0961
D
Silvestro
Smithsonian Tropical Research Institute, 0843-03092 Balboa, Panamá;
Carlos
C
Jaramillo
Department of Ornithology, American Museum of Natural History, New York, NY 10024; Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803; and.
Brian Tilston
BT
Smith
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803; and.
Prosanta
P
Chakrabarty
Department of Biological and Environmental Sciences, University of Gothenburg, SE-413 19 Gothenburg, Sweden; Gothenburg Botanical Garden, SE-413 19 Gothenburg, Sweden.
Alexandre
A
Antonelli
D063147:Animal Distribution; D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D002980:Climate; D005580:Fossils; D005843:Geography; D008322:Mammals / Q000502:physiology; D008954:Models, Biological; D010176:Panama; D058974:Phylogeography
biogeography; evolution; fossil; migration; neotropics