ANN ARBOR—Celebrated in Buddhist temples and cultivated for its wood and cottony fibers, the kapok tree now is upsetting an idea that biologists have clung to for decades: the notion that African and South American rainforests are similar because the continents were connected 96 million years ago.

Research by University of Michigan evolutionary ecologist Christopher Dick and coworkers shows that kapok—and perhaps other rainforest trees—actually colonized Africa after the continents split, as a result of seeds traveling across the ocean.

The findings were published online June 7 in the journal Molecular Ecology.

“Our study shows how oceanic dispersal links the world’s rainforests, and it’s one of the first to catch oceanic dispersal in action at the species level for a rainforest tree,” said Dick, an assistant professor of ecology and evolutionary biology and an assistant curator at the U-M Herbarium. “Although single seeds are very unlikely to survive an oceanic voyage and then successfully establish, such improbable events become probable when summed over 10 to 15 million years.”

Dick studied the rainforest form of Ceiba pentandra, a species of kapok that grows taller than a 16-story building, with its head poking above the forest canopy. Its flowers produce more than 50 gallons of nectar per tree in a season, attracting bats that travel as far as 12 miles between trees and transfer pollen in the process. When the seed pods ripen, they break open to reveal fluffy fibers that are used to stuff pillows and mattresses. The seeds, which are about the size of an unshelled sunflower seed, are buoyant and able to float down rivers along which the colossal trees grow.

In the just-published research, Dick and collaborators at the Smithsonian Tropical Research Institute and the Instituto Nacional de Pesquisas da Amaz