"Agathis probably existed in all three areas, Australia, Antarctica and South America, at that time," said Wilf. "Climate change in Antarctica -- the cold and ice -- killed them there, and a change to seasonal dryness in southern South America put an end to them in Patagonia."
Subsequently, the trees, which are wind dispersed, moved away from the cooling south, and some left northward-moving Australia for southeast Asia, where they thrive except for human interference, but they no longer grow in cold, often dry, Patagonia.
Wilf's team recovered not only leaves, but also numerous branches, pollen cones, seed cones and even a winged seed still attached to the cone. The various species of Agathis are usually identified by their pollen cones, so this is the first time that a fossil Agathis could be directly compared to trees growing today.
"We also went to Borneo and studied the most similar living relative of the fossil Agathis, a threatened species there," said Wilf. "We collected DNA samples to better understand the fossil-modern relationship."
According to the researchers, the Argentinian fossil Agathis clearly belongs to the same natural group as those living today up to almost 10,000 miles away in the tropical West Pacific.
"Agathis is a very dramatic example of survival via huge range shifts, from the far south to the tropics, in response to climate change and land movement over millions of years," said Wilf. "It is not clear that Agathis can adapt to the severely more rapid human-induced pressures it is experiencing now from deforestation, selective logging and climate change."
Also working on this research are Ignacio H. Escapa and Rubén Cúneo,Consejo Nacional de Investigaciones Científicas y Técnicas and Museo Paleontológico Egidio Feruglio, Chubut, Argentina; Robert M. Kooyman, National Herbarium of New South Wales, Sydney; Kirk R. Johnson, Smithsonian Institution; and Ari Iglesias, Consejo Nacional de Investigaciones Científicas y Técnicas and División Palontología, Universidad Nacional del Comahue, Río Negro, Argentina.
The National Science Foundation, the David and Lucile Packard Foundation, National Geographic Society, University of Pennsylvania Research Foundation and the Andrew W. Mellon Foundation supported this work.