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DURHAM, N.C. – Few regions on Earth are as biodiverse as the tropical Andes, nor as baffling to researchers trying to map the evolution and distribution of thousands of scattered rare and endemic species found there.

A new peer-reviewed study, published online July 17 in the Proceedings of the National Academy of Sciences (PNAS), may hold a missing piece of the puzzle.

It shows how the Andes’ complicated geological history and climatic swings have forged a patchwork of distinct regions divided by natural barriers – rugged mountains, steep slopes and swift rivers – each driving the evolution of a unique combination of species.  

The Andes’ geological history and climatic swings have created 15 distinct biogeographical regions. (Credit: Duke Univ.)

“We identified 15 biogeographical regions resulting from Andean uplift and the pronounced temperature oscillations of the Pleistocene era, and we developed three main models of speciation that explain the origin of the biodiversity within these regions,” said Rubén Palacio, a doctoral student at Duke University’s Nicholas School of the Environment, who was one of four authors of the paper.

The Pleistocene era ended about 11,700 years ago and spanned a period of about 2.5 million years when Earth experienced its most recent Ice Age and glaciers repeatedly advanced and retreated across much of what is now the tropical Andes – drastically reshaping its topography.

The impassible barriers created by these forces limited the dispersal of many animals and confined them to smaller and smaller ranges. It also divided some species into isolated local populations. Over time, these geographically separated populations evolved from one species into two closely related species – sister species – in a process scientists call vicariance.      

“Some of these species are only found in one or two biogeographical regions, making them highly vulnerable to extinction if their habitats are not protected,” Palacio said.

The new study used bird species as a model for tracking faunal evolution in the Andes, but the methods Palacio and his colleagues used to conduct their research aren’t restricted to studying birds. They are broadly applicable for studying the complex mechanisms driving isolation and diversification of other species, as well.  
“Using high-resolution species distribution modeling and dated molecular phylogenies, we were able to map the distinct bioregions and track the history of species dispersal and vicariance that has occurred in each region over different periods of time,” Palacio said.  “It’s a recipe for high endemism and diversity,” he added.

“These findings will help set conservation priorities that better preserve the evolutionary patterns of biodiversity,” he said.

Palacio conducted the study with Nicolas A. Hazzi, a doctoral student in biological sciences at George Washington University; Juan S. Moreno of the nonprofit Fundación Ecotonos in Cali, Colombia; and Carolina Ortiz-Movliav, a master’s student in biology at the University of Bonn in Germany. Hazzi was lead author.

All four authors are founding members of Fundación Ecotonos and they began this research under its auspices. Palacio currently serves as the foundation’s scientific director.  

In addition to being published online in PNAS on July 17, the new study is slated to be the cover article in next week’s print edition.



CITATION: “Biogeographic Regions and Events of Isolation and Diversification of the Endemic Biota of the Tropical Andes,” by Nicolás A. Hazzi, Juan Sebastián Moreno, Carolina Ortiz-Movliav and Rubén Dario Palacio; Proceedings of the National Academy of Science, July 17, 2018. DOI: