By Rick Weiss
Washington Post Staff Writer
Monday, January 28, 2008

It started as a simple family picnic in the outback of Madagascar, off Africa's southeast coast. Xavier and Nathalie Metz, local cashew farmers, stared in disbelief at a 30-foot-tall mass of flowers and fruits sprouting gloriously from the top of a 30-foot-tall palm tree.

They had seen the same tree on an outing a year earlier, when it was not in bloom, and had presumed it to be a species common to that region. But the enormous floral display -- literally dripping with nectar and teeming with insects and birds -- convinced them on that day in 2006 that they were witnessing something rare.

Adding to their sense of awe was what they found on follow-up visits: Having thrown itself so completely into that spectacle of reproductive ardor, the huge tree soon collapsed in a depleted heap and died.

Now, scientists have confirmed just how unusual that tree was, and how rare are the 92 surviving specimens that have since been found.

The palm, which researchers say essentially "flowers itself to death," is not only a new species. It has forced palm biologists to invent an entirely new genus to accommodate it. That is an almost unheard of event in modern palm tree classification, but one made necessary by its many unique traits and by DNA testing suggesting the tree has been evolving independently of other palms for millions of years.

"For botanists, it's equivalent to finding a large mammal, or a new kind of elephant even, in some unexpected place," said William Baker, a palm biologist at Kew Gardens in London, which has been a key player in bringing the weird tree to scientific light.

The discovery, documented in the Jan. 17 issue of the Botanical Journal of the Linnean Society, is bringing new attention to palms, an ancient and biologically peculiar family of flowering plants. It is also helping to highlight the predicament Madagascar faces as population growth, poverty and poor land management conspire to destroy the last vestiges of that island's ecological magnificence.

"So much of Madagascar's landscape is absolutely shattered by human activity," said Scott Zona, a palm biologist at Florida International University in Miami. "These palms were growing at the base of a little hill, nestled in a ravine, and were protected from the fires and cultivation that have been going on there. The area is all rice paddy now but was probably a forest that was full of this palm."

An estimated 90 percent of Madagascar's 10,000 plant species are found nowhere else in the world. Yet a mere 18 percent of the island nation's native vegetation remains undisturbed by human activity, and one-third of its vegetative cover has disappeared in the past three decades alone, according to surveys and satellite imagery.

About 200 species of palms can be found on Madagascar, and a recent survey had filled in what palm scientists thought were the last holes in their tally there.

Then, in December 2006, a palm enthusiast living on the island saw some pictures that the Metzes had taken on their picnic and posted them on PalmTalk, the interactive online chat room moderated by the International Palm Society.

"I could hardly believe my eyes when I saw the images posted on the Web," said John Dransfield, a research fellow at Kew and co-author of the Field Guide to the Palms of Madagascar. "Clearly this was going to be an exciting discovery, and I just couldn't wait to examine the specimens in detail." A Kew PhD student doing research in Madagascar was called upon to hike into the area, retrieve samples and send them to England. Careful analysis of the stems, leaves and other parts, along with DNA analysis, confirmed that the tree belongs in a genus of its own -- one that has been given the name Tahina, which in the Malagasy language means "to be protected."

Tahina spectabilis (from the Latin for "spectacular") is a huge palm, with fan-shaped leaves as big as 15 feet across. As is the case with most palms, the leaves are arranged in a way that appears to minimize the amount they shade each other. So big is the green footprint of the few newly discovered specimens that people who know what they are looking for can spot them on Google Earth.

T. spectabilis is one of just a few species of "suicide palm" worldwide: trees that grow for decades, then throw every last bit of energy they have into an ultimately fatal reproductive frenzy. Some scientists call it "explosive" or "big bang" reproduction, but it is a slow-motion explosion, in which hundreds of thousands of flowers will bloom, attracting pollinators that, depending on the palm, may be beetles, bees or bats.

In all palms, those flowers become seed-laden fruits. Some, such as coconuts, have evolved a capacity to float far away. Most palms, including Tahina, produce fleshy fruits (in Tahina's case, about an inch across) that are eaten by birds and small mammals, which then disperse the seeds.

But that relatively limited capacity to spread their seeds raises one of the biggest mysteries about Tahina: How did it get to Madagascar? The three genera of palms most closely related to it, and with which Tahina must share a common ancestor, all live far away, in Central Asia, China and Thailand. Some suspect a seed may have rafted across a huge expanse of sea. Others wonder whether the ancestor originated on Madagascar, and some specimens rode northward on fragments of a continent that broke up more than 100 million years ago, portions of it drifting toward Asia.

"It just shows how little we know about these organisms, even those that are so big and showy," said Andrew Henderson, a curator at the New York Botanical Garden, who called the find "an amazing discovery, totally unexpected." No one knows how old Tahina must get before it flowers. Unlike most trees, palms do not have tree rings that allow scientists to check their age. That is because palms remain underground during their first years of life, until their trunks have reached their full adult girth. Only then do they grow skyward.

But scientists suspect that flowering events in Tahina are rare, because native residents say they have never before witnessed it.

That has helped energize an effort to preserve what is left of Tahina on Madagascar and to cultivate the seeds that have been collected.

Local people have constructed a stockade around the trees to protect them from cattle. And Kew is helping coordinate a program through which nearby farmers can sell the seeds to botanical gardens and researchers around the world.

"We'd really like to see the local people getting a good share of the profits for that," Baker said. "They are very much into this palm and very proud of it."