Thursday, May 18, 2017

Space Invaders: Graduate Student Maps Genetic History of Water Hyacinth


Elliot Weidow dipped the end of an eight-foot aluminum pole into the giant water hyacinth mat that had nearly overtaken a canal running through New Orleans City Park’s Couturie Forest. The coat-hanger hook he’d fashioned on the end of the pole drew up a dripping specimen, its dark brown roots sprouting like hair under the waxy green leaves.

About 10 days earlier, Weidow said, there was notably less hyacinth floating about in this spot. Yet the plant quickly multiplied as it always does, turning the waterway into a crowded channel of perky aquatic greenery with its occasional purple flower.

For such a pretty plant, the water hyacinth has become a notorious nuisance.

“It easily makes top 10 in the worst invasive species on earth,” said Weidow, a master’s student in the University of New Orleans Department of Biological Sciences, who recently received a $1,200 Louisiana Environmental Education Commission grant to research the plant’s genetic diversity through history.

The water hyacinth was introduced to the United States through New Orleans in 1884 during the World’s Industrial and Cotton Centennial Exposition, according to records. Weidow said that research often describes it being brought in by “Japanese entrepreneurs” who gave it away as a gift to attendees. But the hyacinth is native to South America, where it provides steady nourishment to its Amazon River predators who managed to keep it controlled.

In its 133-year existence in North America, however, nothing has been able to effectively halt the growth of the water hyacinth, also known as Eichhornia crassipes. It takes over waterways in thick blankets, blocks light that other plants and animals need to survive, sucks oxygen from the water as it sinks and decays and ultimately suffocates fish populations that need the oxygen to live. It makes waterways difficult—sometimes impossible—for boats to navigate, interferes with the livelihood of sustenance fishers and is known to block drainage canals and ditches.

Weidow said the plant’s stubborn hardiness leads him to want to dig deeper.

Water hyacinth reproduce asexually, cloning themselves without the need for germinating seeds. As such, it seems the plant should lack genetic diversity, making it ecologically more vulnerable. But its long history here—and now in every other continent except Antarctica—indicates a stubborn unwillingness to cave.

Weidow suspects that is because the plant is more diverse than scientists understand. He wonders if the conditions of Louisiana’s flood cycles might have created the rare conditions the plant needs to create seeds and repopulate sexually, as it does at times in the Amazon.

“We do get a little bit of that down here,” Weidow said. “No one has directly tried to characterize it, but it might be happening … That would be something that would drive up diversity, this breeding and intermixing of genes.”

He is also asking questions like whether the 1884 event was the only time the plant was introduced to North America, or if there have been multiple releases over time. Does the plant have the potential to adapt and evolve traits like frost resistance, salinity tolerance and herbicide resistance?

In order to get to the bottom of that, Weidow is mapping the plant’s genetic history. He’s turned to regional herbariums—which are like a cross between plant museums and plant libraries—to collect 150 dried specimens through history. The oldest specimen he’s found is from 1894. By looking at the DNA of these plants, he hopes to get more information about its diversity over time.

In addition, he is collecting his own contemporary specimens, like this one he’s pulled from the water at City Park. Every couple of months, he makes the rounds to waterways in and around City Park, Jean Lafitte National and Historical Park, Lacassine National Wildlife Refuge, Lake Pontchartrain and Hattiesburg, Miss. He dips his make-shift pole in, pulls up a plant, inspects its appearance, records its GPS coordinates, and tears off a leaf that he places in a specimen bag.

Growing up in a Maryland family that enjoyed time camping and hiking together, Weidow said he was naturally drawn to biology as a field of study. He majored in biology and philosophy at Frostburg State University in western Maryland. After a summer internship spent dragging ladders through West Virginia forests in pursuit of flying squirrels, he determined plants were more his style. “I really fell for plants,” he said. “You can find it, tie a ribbon on it and it stays there—and it’s fantastic.”

Weidow volunteered for two years in Americorps and the Chesapeake Conservation Corps, which intensified his interest in restoration, ecology and invasive species. He enrolled in UNO’s graduate school in the spring of 2016 and said he’s really enjoyed working with and under Jerome Howard, associate professor of biological sciences.

Ultimately, he says he hopes the research he’s doing under Howard will provide more useful information for controlling the water hyacinth while keeping long-term sustainable management in mind.

“Given the financial and environmental costs of controlling E. crassipes, it is critical to make management decisions informed by research specific to their region,” Weidow wrote in a research summary about the project. “Not only will this research help local decision makers, but it will help with the global management of a significant aquatic pest plant.”

Asked what he will do if the genetic history study indicates the plant has developed resistance attributable to genetic diversity through time, Weidow smiled and laughed.

“That’s a good question,” he said. “Then, I will probably roll into a Ph.D.”

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University of New Orleans College of Sciences
University of New Orleans Department of Biological Sciences
University of New Orleans Graduate School
University of New Orleans Office of Research and Sponsored Programs