The study analyzed the genomes of more than 100 varieties of modern maize and 11 ancient plants. The researchers discovered several distinct lineages, each with their own unique relationship to teosinte. The results also revealed that although maize domestication began with a single large gene pool in Mexico, the grain was carried elsewhere before the domestication process was complete.
According to the study, there was a major wave of "proto-corn" movement from Mexico to South America, where the domesticated maize landed in the southwest Amazon, a hotspot for the domestication of other plants, including rice, squash, and cassava. Kistler said that it is possible, though not certain, that maize in this new location evolved more quickly than maize in the center of domestication. After incubating in southwest Amazon for several thousand years, maize moved to the eastern Amazon. The researchers also discovered that modern maize from the Andes and southwestern Amazon is closely related to maize grown in eastern Brazil, pointing to another eastward movement.
Jeffrey Ross-Ibarra, a plant scientist at the University of California, Davis said that the team's work shows how maize continued to evolve after it arrived in South America. "While not a second domestication per se, it does highlight that South American maize has undergone a considerable amount of adaptation somewhat independently of maize in Mexico," he adds.
For more details, read the news release from the Smithsonian.