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Researchers Find Regenerating Tropical Rain Forest Lacks Genetic Diversity, Increasing Chance Of Extinction
Released: February 9, 2005

Release #05004
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STORRS, Conn.— The findings of three University of Connecticut researchers, to be published in the Feb. 11 issue of the prestigious journal Science, suggest that the next generation of tropical rain forests may not be nearly as healthy as they seemed at first glance.

Ecologists, including UConn’s Professor Robin Chazdon, who has studied the regeneration of tropical rain forests in Costa Rica for 15 years, initially were encouraged by the speed with which some species of trees were reappearing in areas once cleared for farming or ranching. But, in recent years, scientists have begun questioning the genetic diversity found in the newer rain forests they call “second-growth” forests.

Under the guidance of Department of Ecology and Evolutionary Biology professors Robin Chazdon and Kent Holsinger, doctoral student Uzay Sezen applied the same DNA analysis techniques used in criminology and human paternity tests to determine parenting patterns in regenerating forests. While other scientists have begun studying the genetic diversity of second-growth forests, the trio’s study is ground-breaking because it is the first to pinpoint which trees in a mature rain forest parented offspring in a second-growth forest.

Their finding – that seeds from just two canopy palm trees out of 66 found in a mature rain forest at La Selva Biological Field Station in Costa Rica produced more than half the

founding generation of palms in a nearby, second-growth forest – points to a severe lack of genetic diversity and is cause for real concern, Chazdon and Sezen said.

“If this trend that we found is a common thing, then it’s something very serious,” Sezen said.

Tree populations that lack genetic diversity are far more susceptible to disease, pests, drought and other global changes, increasing the chance for extinction, Chazdon said.

That possibility is particularly alarming because second-growth rain forests now outnumber mature rain forests.

“Most of the tropical forests we’re going to have left in the future are like this one,” she said. “Those forests will be the ones available where people will be able to take walks or to get wood, to get products.”

So far, Sezen, Chazdon and Holsinger have studied the genetic make-up of just one species of palm tree in one part of Costa Rica, but the researchers believe the study has far-reaching implications for several reasons. The particular palm – known as the Iriartea – makes up between 5 and 10 percent of the rain forest trees throughout Central and South America and is found from sea level to 4,000 feet high in the mountains. Additionally, the study area, in a well-protected field station in Costa Rica, represents a best-case scenario for the regeneration of tropical rain forests because the field station and adjacent Braulio Carillo National Park contain large areas of mature rain forests and have an abundance of birds and other mammals to distribute the seeds that sprout new trees.

Publication of these findings comes on the heels of an international conference on biodiversity, held in Paris last month, where scientists and world leaders cautioned that plant and animal species are being lost at a rate 100 times faster than the average rate during the Earth’s history. Experts at that conference also stressed that the effects of biodiversity were evident in the Dec. 26 tsunami, where regions with more mangroves and coral reefs were spared the worst of the devastation.

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