"With the results we present in this article, we've rewritten the entire history of Amazonia in terms of the development of its biodiversity," Alexandre Antonelli of the university's Department of Plant and Environmental Sciences and scientific curator at the Gothenburg Botanical Garden explained in a statement on the team's findings.
While researchers have long suspected that the diversity of the Amazonian rainforest was influenced by the Andes, the causal links have remained the subject of debate. The new findings put to rest a debate that has persisted over the last 40 years concerning the origins of the Amazon rainforest.
"This settles old debates and is the final say on this," Antonelli told The Local on Wednesday.
Brazilian native Antonelli and Carin Hoorn of the University of Amsterdam led the team, which compared over the last year and a half the pattern of modern biodiversity in the Amazon with geological and molecular data spanning the last 65 million years following the separation of South America from Africa and the extinction of the dinosaurs.
"We suspected from some scattered fossils and dated species trees that the Amazonian diversity arose after the separation from Africa, so we looked at the whole period," explained Antonelli.
Antonelli focused his research on coordinating a survey of DNA-based studies of relationships between plants and animals and came up with some interesting results.
"We've examined hundreds of scientific publications and have found that very few of the genera are as young as people thought."
Previously, the one dominating theory, the refuge theory, attributed the Ice Age to the region's high diversity, he told The Local.
The results of the research show that the greatest biodiversity is found in connection with the Andes, an area that formed when the tectonic plates along the Pacific coast were pressed together to create the mountain range.
The new mountains had a major impact on the environment, changing living conditions fundamentally for plants and animals in the Amazon rainforest, Antonelli said.
The restructuring of the earth's crust changed the large wetland areas found in the northern part of South America, which dried up as the Amazon River formed. In turn, this opened up new land for colonisation by plants and animals.
"We were surprised that there was such a strong link between the formation of the Andes and the diversity in Amazonia. The area was considered a kind of paradise where evolution could take place undisturbed, but this hasn't been the case at all – a lot has happened in the region," said Antonelli.
Antonelli's team included 18 researchers from the Netherlands, Switzerland, Spain, the UK, Sweden, Brazil, Colombia, Panama, Venezuela and the US from various disciplines, including molecular biology, geology, paleontology, zoology and statistics.
The fossils from 55 million years ago revealed that the region was much more diverse then than it is now.
"Species go extinct. They do that all the time, but they are replaced by new species. We do know there has been a lot of extinction and habitat destruction, but extinction rates are much higher now than they've ever been as a result of human influence excluding mass extinction events," Antonelli told The Local.
He hopes his findings will help aid in focussing on preservation efforts, particularly in western Amazonia, which is very overlooked.