Alumni Association Home > Past Issues > 2006 > March-April 2006	Print View

Diversity isn’t just a nice idea. Apparently, Mother Nature demands it.

An analysis of seven tropical forests around the world has revealed that nature encourages biodiversity by favoring the growth of rare trees over common ones. The landmark study, conducted by 33 ecologists from 12 countries, conclusively demonstrates that diversity matters and has ecological importance.

Helene Muller-Landau, an assistant professor of ecology in the University of Minnesota’s College of Biological Sciences, is a co-author of the study, which supports previous research by her colleague David Tilman, a Regents’ professor of ecology, into the causes and value of biodiversity.

The study was conducted on seven undisturbed forest plots, or “tropical forest observatories,” in Borneo, India, Malaysia, Panama, Puerto Rico, and Thailand. The plots themselves are diverse, ranging from dense and species-rich wet rainforest to drier and more open forest that is often swept by fires. Yet all the forests show the same pattern of increasing local diversity as trees age.

“[These findings] highlight the value of the large-scale, long-term, standardized data collected by my collaborators,” said Muller-Landau. “This is a unique effort in many ways—multiple large studies in multiple countries are censusing trees according to the same methods,” including, at each site, tagging, mapping, and identifying to species every tree greater than one centimeter in diameter and then measuring each tree every five years.

“This research has the surprising finding that biodiversity in tropical rain forests and Minnesota prairies arises from the same kinds of underlying processes,” said Tilman, director of the Cedar Creek Natural History Area, an ecological research site in Minnesota. “It brings us a step closer to understanding the causes of the world’s amazing biodiversity.”

Lead author Christopher Wills of the University of California–San Diego said the study answers a question that ecologists have debated for decades: Is there something of ecological value to species diversity? The answer, he said, is yes. “We found that, in forests throughout the New and Old World tropics, older trees are more diverse than younger ones,” he said. “In other words, diversity is actually selected for as each of the forests matures. This means diversity does indeed matter and is an essential property of these complex ecosystems.”

Researchers do not fully understand why that is so, but one possibility is that animals, fungi, bacteria, and viruses are less likely to cause damage when their hosts are rare. Another possibility is that members of different species don’t compete as much as members of the same species.

Researchers note that diversity-enhancing processes are likely to be absent from badly damaged forests. When forests are clear-cut, for example, the soil is rapidly depleted of nutrients, and the insects, bacteria, and fungi that help sustain diversity disappear. However, the study also suggests that tropical forests that have been damaged only slightly are resilient and can regain their former levels of diversity.

Wills said the new study points the way toward further detailed investigations of the processes by which forest diversity is maintained and raises new questions and lines of research for ecologists and forest managers to pursue.

—Cynthia Scott

Combating a Hefty Occupational Hazard

Bus drivers are among the most vulnerable workers when it comes to gaining weight as a result of work conditions, according to a new study by the University of Minnesota and the Metro Transit Commission (MTC). The study found that while 63 percent of the general population is overweight, 89 percent of Twin Cities bus drivers are. Long periods of sitting, split shifts, short breaks, and fast food all contribute to the problem.

A joint U of M/MTC initiative called Route H—the “H” stands for healthy—seeks to create a healthier work environment for drivers. Some of the changes envisioned include revamping vending machines to include more healthful options, upgrading fitness rooms, and introducing physical activity programs at work, such as intramural sports and walking clubs. Researchers want the study to help drivers at least maintain if not lose weight. They also want to create strategies to help the transportation industry overall provide a healthier environment for employees. The impact of the changes will be measured over the next two years.

Students with Disabilities Improve Academically

Nationwide, the percentage of students with disabilities—including physical, emotional, cognitive, and learning—achieving proficiency on state accountability tests has increased for the first time in 14 years, suggesting that they may be able to perform at the same level as other students.

That is one conclusion of a report released by the University of Minnesota’s National Center on Educational Outcomes. The report summarizes a survey of state directors of special education in all 50 states. Among the reasons given for students’ improvement are better alignment of students’ Individual Education Plans with state standards, increased access to standards-based instruction, and improved professional development for teachers.

Special education has historically been synonymous with “special curriculum” that was different from the general curriculum. The shift to standards-based education has given rise to the expectation that all students will work toward the same skills and knowledge and thus have access to the general curriculum.

The National Center on Educational Outcomes was established at the University in 1990 to provide national leadership in designing and building educational assessments and accountability systems that monitor educational results for all students, including students with disabilities and students with limited English proficiency.

Hope for Compulsive Gamblers

Researchers at the University of Minnesota have achieved promising results with a pill to treat pathological gambling, a psychiatric condition associated with financial difficulties, lying, increasing the amounts of bets, time spent gambling, and thinking about gambling. It is estimated that about 2 percent of the adult population, or 6 million people, suffer from pathological gambling.

The pill, nalmefene, works by blocking the rush associated with gambling and curbing the craving to gamble. The trial involved 207 participants in 15 outpatient treatment centers across the United States. Participants took the pill daily and over a four-month period reported significant improvement in gambling urges, thoughts, and behavior. Researchers believe these findings may eventually help treat other addictive behaviors as well. Read more here.

Honest, Abe’s DNA Leads to Breakthrough

A study at the University of Minnesota that relied on DNA samples from descendants of Abraham Lincoln has produced promising findings for sufferers of ataxia, an incurable, degenerative brain disease that affects movement and coordination. Researchers at the Medical School identified a gene responsible for Spinocerebellar ataxia type 5 (SCA5) by collecting and analyzing DNA samples from more than 300 descendants of President Lincoln.

The discovery provides a genetic test that will lead to improved patient diagnoses and gives researchers greater insight into the causes of ataxia and other neurodegenerative diseases—and advances the development of effective treatment. The findings could also provide historical insight, since there are descriptions of Lincoln having an uncoordinated and uneven gait. These could be early symptoms of SCA5.

Shedding Light on the Midnight Snack

Habitual indulgence in a midnight snack can be linked to psychiatric disorders, according to research conducted at the University of Minnesota Medical School and the University of Pennsylvania School of Medicine. Researchers found that “night eating syndrome”—a condition characterized by excessive eating in the evening (called hyperphagia) or waking up during the night to eat—is common among people with substance abuse, depression, and other psychiatric disorders. People in the study, all of whom were being treated in outpatient psychiatric clinics in Minnesota and Pennsylvania, were diagnosed with night eating syndrome if they showed either or both of the characteristics three or more times per week.

Approximately 1.5 percent of the general population and 9 percent of patients in obesity clinics have night eating syndrome. But the recent study found that more than 12 percent of participants in an outpatient psychiatric clinic had the syndrome. Substance abuse, particularly alcohol, was also more likely to occur among patients with night eating syndrome. The published results encouraged mental health practitioners to screen patients for night eating syndrome.

Kiss Those Symptoms Goodbye

Researchers at the University of Minnesota have found an antiviral drug that is effective in treating infectious mononucleosis, an affliction that up until now has been notoriously resistant to drug treatment. Mono, sometimes called “kissing disease” because it is spread through saliva, is caused by the Epstein-Barr virus, a member of the herpes virus family. It typically strikes adolescents and young adults, causing severe fatigue, sore throat, headache, loss of appetite, swollen glands, and fever.

University of Minnesota researchers found that sufferers who took the drug valacyclovir experienced less severe symptoms and recovered sooner than those who took no drugs or who took a steroid, commonly prescribed to reduce symptoms. The study also suggests that valacyclovir can limit person-to-person spread of the disease.

Despite the popular association of mono with kissing, puckering up is not the most common means of transmission. The disease is also spread by coughing, sneezing, and sharing a glass or cup. It is not a highly contagious disease. Read more here.