A team of researchers led by University of Chicago Ph.D. candidate Kieran Althaus, an affiliate of the Arboretum's Science and Conservation Department, uncovered the conditions that enabled oaks to rapidly diversify in the Americas. The findings have advanced scientific understanding of the origins of one of the world's biodiversity hotspots, forming a unique case study for evolution at a global scale.

The paper, "Timing and origins of Mexican and Central American oak diversity," published in the Proceedings of the National Academy of Sciences (PNAS), revealed that oak lineages were able to very quickly adapt—in terms of tree time—when they encountered high-elevation terrain.

"The fastest expansion of oak diversity anywhere in the world has taken place in Mexico and Central America, revealing the importance of this region for these keystone species," Althaus said. "Mountain ecosystems prove key to generating oak diversity."

According to the authors, oaks' movement into rugged and complex habitats, combined with their high level of adaptability to new climates, facilitated the formation of a vast oak diversity hotspot. Using data from 322 of the world's approximately 450 oak species, the researchers carefully reconstructed oak evolutionary history.