A pale green fern found (above) on the forest floor of the Pyrenees has surprised researchers by proving to be a cross between an oak fern and a fragile fern.
These two fern groups are distantly related and grow across much of the northern hemisphere – going their separate ways about 60 million years ago. Botanists had believed it was impossible for two species to reproduce after such a long time.
Kathleen Pryer who directs the Herbarium at Duke University co-wrote a study of the fern to be published in American Naturalist. She likened the cross-breeding of the ferns to an elephant breeding with a manatee or a human with a lemur.
Her co-author, Carl Rothfels of the University of California said: “To most people they just look like two ferns, but to fern researchers these two groups look really different.
“For most plant and animal species, reproductive incompatability takes only a few million years at the most.”
Before the discovery of the fern, the most extreme recorded examples of breeding between different groups have been a hybrid tree frog that came about after a 34 million year separation and a hybrid sunfish that appeared after almost 40 million years.
Ferns only require wind and water to reproduce in contrast to flowering plants that require animal pollinators. Flowering plants outnumber ferns by 30 to one, but ferns have been on the Earth for much longer.
More on ferns from Cosmos: How ferns learnt to live in the shadows