'Weird' Fern Shows The Power Of Interspecies Sex

Feb 24, 2015
Originally published on February 24, 2015 9:48 am

The love between two ferns knows few bounds, it appears. A DNA analysis of a hybrid fern shows that its parents are two different species separated by nearly 60 million years of evolution.

"A 60 million year divergence is approximately equivalent to a human mating with a lemur," says Carl Rothfels, a fern researcher at the University of British Columbia, who headed the study. The hybrid is a record, he says.

The freak fern, known as Cystocarpium roskamianum, isn't rare. It can be found spreading its fronds across the French Pyrenees. You can even buy it at some European garden centers, Rothfels says.

But fern researchers have always thought it looked sort of weird.

"I mean, on one level it looks like a fern," Rothfels admits.

But he says this type of fern appears to have come from two parents that you wouldn't expect to be a couple. One lives on rocky outcrops. The other is found on the floors of forests. They are two different species from different places, and yet somehow they get together to make this hybrid.

"It is pretty much exactly between the two parents," he says

The team's DNA analysis confirming the odd coupling is published in the March edition of the journal The American Naturalist.

"Ferns are unique among plants for many reasons, and this study adds another potential difference to the list," says Emily Sessa, a researcher at the University of Florida in Gainsville. Apparently, ferns do not easily evolve barriers that keep them from interbreeding.

That flexibility could help explain why there are only 10,000 species of ferns on the planet, as opposed to some 250,000 species of flowering plants, adds Robbin Moran, curator of ferns at the New York Botanical Garden.

Rothfels says the hybrid fern is sterile, though it can reproduce "vegetatively" by sending out runners across the ground.

"It seems to be quite happy," he says.

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RENEE MONTAGNE, HOST:

NPR is committed to bringing you all the news. And that includes news about houseplants. This morning, ferns. NPR science correspondent Geoff Brumfiel reports on some new findings that have fern researchers, as Jeff puts it, frontic.

GEOFF BRUMFIEL, BYLINE: Get it? Frontic instead of frantic because ferns grow fronds instead of leaves. Yeah. Anyway, Carl Rothfels is at the University of British Columbia. He's devoted his entire career to studying ferns, and he's heard all the bad fern puns before.

CARL ROTHFELS: Frondly persuasion, things like that, anything that uses frondly or friendly.

BRUMFIEL: But it's been worth it because Rothfels and his fellow researchers have made a remarkable discovery about a very odd fern.

ROTHFELS: It's something called Cystocarpium roskamianum.

BRUMFIEL: It's found in France, and it's fairly common. You can even buy it at some European garden centers. But to fern researchers, it looks weird.

ROTHFELS: Yes, it looks really weird. I mean, on one level it looks like a fern...

BRUMFIEL: Quick aside - to me, it looks like a normal fern. But Rothfels says this fern appears to have come from two parents that you wouldn't expect to be a couple. One lives on rocky outcrops. The other is found on the floors of forests. The two are different species from different places, and yet somehow they get together to make this hybrid.

ROTHFELS: It is pretty much exactly in between the two parents.

BRUMFIEL: The team's DNA analysis confirmed it. This crazy hybrid has fern researchers talking. But the reason I'm talking about it on NPR is even crazier. The genetics show the parent species are really far apart.

ROTHFELS: These two ferns had been evolving independently for about 60 million years before they got back together again and were able to form this hybrid.

BRUMFIEL: Sixty million years, and they could still make a baby fern. That's a record. And to put it in perspective - humans and lemurs have been evolving separately for 60 million years. We definitely cannot make little baby Leemans.

ROTHFELS: Another, at least, approximately comparable example would be an elephant mating with a manatee.

BRUMFIEL: Which would be an elephanatee?

ROTHFELS: Yeah, right. I don't know what would happen. That's well done, though. That was almost as good as the fern puns.

BRUMFIEL: How is it even possible that ferns can do this? Truth is, Rothfels isn't sure. All ferns do share a similar reproductive process, so it could be that a rock-fern sperm can't tell the difference between the egg of a rock-fern and one of a forest-fern, which, he says, raises an interesting possibility - perhaps more distant hybrids would be possible with other species if they just gave it a try.

Are you saying that if we did get an elephant and a manatee together...

ROTHFELS: We'd get an elephanatee? I think most people would say that that's impossible.

BRUMFIEL: But it might be possible that other ferns could get together, and their hybrids might teach researchers about how evolution and reproduction work. Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.