Monday, 15 November 2010
Source: Cosmos
SYDNEY: The gradual rise of the Andes Mountains, which took place over millions of years, created conditions necessary for the Amazon to develop its rich biodiversity, according to a new study.
Drawing on a vast body of multidisciplinary research, a group of scientists claim that the region’s extraordinarily diverse ecosystem is much older than previously thought, as they wrote in a review article in the journal Science.
“In the past decade, several explanations have been given on an old origin of Amazonian species diversity but the geological mechanisms behind the evolution of biodiversity were never deeply explored.
More than 20 million years
"We have done that and show that modern landscape, flora and fauna developed in parallel with the uplift of the Andes,” said Carina Hoorn, a palaeoecologist at the University of Amsterdam, and lead author of the study.
The origin and timing of biological diversification in the Amazon rainforest has been the subject of contentious debate, with most studies tending to focus on the relatively recent Pleistocene epoch - 1.8 million to 10,000 years ago.
By finding a causal relationship between Andean uplift and species diversification, Hoorn and colleagues have shifted attention back more than 20 million years, deep into the pre-Quaternary period.
Most species-rich ecosystem on the planet
To investigate the origins of Amazonian biodiversity, the researchers gathered various geological and ecological data sets and compared them with dated phylogenetic trees that reveal the timing of species diversification in the region.
Their analysis showed that tectonic movement and subsequent uplift in the Andes had a monumental impact on the Amazonian landscape.
By altering drainage patterns and stimulating an enormous influx of sediments, Andean uplift created a mosaic of soils that provided the right conditions for the evolution of an extraordinarily rich assemblage of fauna and flora.
“We show how the process of mountain building throughout the Cenozoic [65.5 million years ago to the present] in the Andes was paralleled by developments in Amazonia. Particularly from 23 million years onwards we show how uplift created new wetland environments in the western Amazon region,” said Hoorn.
Today, this region of the Amazon basin supports one of the most species-rich ecosystems on the planet.
Profound influence
By making the connection between geological history and present day biodiversity, Hoorn and colleagues have demonstrated that future studies into the origins of Amazonian biodiversity must look much farther back in time than they have in the past.
William Laurance, a tropical biologist, from James Cook University in Cairns, who has worked extensively in the Amazon, told Cosmos Online that the research greatly advances “our understanding of the historical forces that have shaped the world’s largest and most biologically diverse rainforest”.
“It would be difficult to name any major group of Amazonian plants or animals whose fate had not been touched in some way by the formation of the vast Andean mountain chain,” said Laurance.
“Many mysteries remain in Amazonia, but it’s becoming clear that geological events such as the Andean uplift and shifts in the courses of major rivers have had a profound influence on the biogeography of the region”.