Student Proves Giant Whorled Sunflower's Extreme Rarity
September 2007 -- For several months last spring, the Vanderbilt greenhouse held more individual plants of a rare species of native sunflower than are known to exist in the wild.
This unusual bounty was the result of research being conducted by Jennifer Ellis, a doctoral student in the biological sciences department.
The species is called the giant whorled sunflower, Helianthus verticillatus. It was discovered in 1892 but was thought to be extinct until 1994 when it was rediscovered in Georgia. Today, it is known to exist in only four locations in West Tennessee, Alabama and Georgia. It has been a candidate for listing as a federal endangered species since 1999.
In the last four years Ellis has conducted a series of genetic studies of the whorled sunflower that significantly improve the odds that this gangly plant will make the endangered species list. Once a species is listed, the federal government is empowered to take a number of steps to protect it.
"Her study came at a perfect time and gave us answers that we really needed," says Cary Norquist, assistant field supervisor and botanist in the Ecological Services Field Office of the U.S. Fish and Wildlife Service in Jackson, Miss. Norquist has recommended upgrading the sunflower's application for listing from a low to a high priority as a result of the new information.
One of the questions that Ellis' research answered was whether the whorled sunflower was a distinct species or a hybrid of two common varieties. If it was a hybrid, it would not qualify as an endangered species. "Her work definitely confirmed that it is a distinct species," says Norquist.
The other answer that Ellis has provided is a more accurate count of the number of genetic individuals that exist in the wild. According to previous estimates, there were several thousand whorled sunflowers growing in Coosa Valley Prairie in Alabama and Georgia, about 7,000 acres of which is owned by Temple-Inland Inc.
The timber company donated a 929-acre conservation easement on the most sensitive portion of that area to the Nature Conservancy in 1992 because of the sunflower population as well as the presence of two other threatened or endangered species (Mohr's Barbara Buttons and Tennessee Yellow-eyed Grass). Even though whorled sunflower population estimates at the other known locations were much smaller, the large size of the Georgia population plus the conservation easement there reduced the sense of urgency attached to its case for listing.
The genetic study proved that the field observations of the sunflower had been misleading. The sunflower propagates clonally as well as by sexual reproduction. As a result, many stalks that appear to be individual plants are genetically identical to their neighbors. "I went out and sampled a whole bunch of stalks and then genotyped them," Ellis says. "I found that the whole population in Coosa Valley Prairie consists of about 20 to 40 genetic individuals. If they have the same genotype, then they are the same genetic individual. There can be ten stalks growing together that you would think are ten plants. But, when you genotype them, you find they are all the same genetic individual."
The fact that there are so few individuals at the Georgia site increases the importance of protecting the other sites, Norquist says.
One hundred of the plants that Ellis grew in the greenhouse are adding to the population in a more direct fashion. She gave them to researchers at Freed-Hardeman University in Henderson, Tenn., who are restoring a wetland that is a suitable environment for the whorled sunflower. They will be using the plants in an experiment designed to identify the environmental variables that have the greatest effect on the sunflower's fitness.
The study had a somewhat haphazard beginning. After getting a biology degree from Carson-Newman College in Jefferson City, Tenn., Ellis started her graduate work at Vanderbilt in 2003. "A lot of people come to graduate school knowing what project they want to do and what professor they want to study with. I didn't. I knew I was interested in conservation biology but didn't have a project," Ellis says.
She spent time working with several different faculty members and settled on Professor of Biological Sciences David E. McCauley. "He works on plant genetics and studies an invasive species, so it was a good match," she says. When she settled in, McCauley suggested that they find a project of her own by contacting the state division of natural areas and asking if they had any research that they needed one on endangered plant species.
It just so happened that Ellis had a contact in the office: Rare Plant Protection Program Manager David Lincicome. When she was still in high school and thinking about pursuing a career in botany, a member of her church put her in contact with the botanist. "She called me up and I described the ins and outs of a career in botany," Lincicome recalls. "I knew she had decided to attend Carson-Newman. Then, four or five years later, she contacted me about possible projects and I talked to her about the whorled sunflower. I had an opportunity to get out in the field with her several times: It's been a good project."
The study proved to be practical and relatively inexpensive because Ellis found that she could apply biomarkers that John Burke — a plant biologist at Vanderbilt who has since moved to the University of Georgia — had developed for studying commercial sunflowers. It would have taken Ellis several years and thousands of dollars to develop a comparable library of genetic markers for the whorled sunflower. But she tested Burke's markers and found that they worked with the wild relative. Her success in applying genetic markers developed for a commercial plant to a related wild species was the subject of a paper that she, McCauley and Burke published in the scientific journal Molecular Ecology in August 2006.
"I've given her advice from time to time, but this has been entirely Jennifer's project," says McCauley.Source : Vanderbilt University.
rating: 4.00 from 1 votes | updated on: 2 Feb 2009 | views: 1274 |