Dec. 13, 2012 From the first time she saw pictures of slime molds, Laura Walker was immediately intrigued.
"They are so cool and so pretty," said Walker, a graduate student at the University of Arkansas working towards a doctoral degree in the department of biological sciences. So far, she has identified six species never before recorded in Panama for her research project, titled "Soil-inhabiting myxomycetes and their shifts in community structure across ecological gradients."
This past summer, Walker became the first scientist to collect slime molds from soils in Panama's Barro Colorado Nature Monument. In doing so, she became one of the first researchers to systematically take samples of slime molds, the most abundant predators of soil bacteria and fungi, in tropical soils.
Slime molds are not plants or animals but they share the characteristics of both. They are found all over the world, yet they remain mostly a mystery to scientists. They come in all shapes and sizes, ranging from yellow-tinted blobs to pinkish spheres.
Walker is studying a group of slime molds known as myxomycetes. Relatively little is known about their exact ecological role in terrestrial ecosystems, and this is especially true for the soils associated with tropical forests.
Walker, from Hannibal, Mo., discovered myxomycetes as an undergraduate at Maryville University in St. Louis, where she graduated with a bachelor's degree in biology in 2004. She was drawn to their shapes, sizes and colors and she bought Steve Stephenson's 2000 book, Myxomycetes: A Handbook of Slime Molds.
"As I learned more and more I found out how amazing they really are," she said. "They eat bacteria and fungi and we know there are a lot of them in the soil but nobody has really paid attention to them. Bacteria and fungi are what decompose everything in the forest, so if myxomycetes are eating them and keeping that population checked they are really important for nutrient cycling and forest productivity. The really fascinating thing about them is they have a really complex life cycle. It's just one cell that keeps getting bigger and bigger. It can be three meters long and it's still just one cell."
Stephenson, a research professor at the University of Arkansas, is one of the world's leading experts in the field of slime mold research. He said Walker's research is important because it represents the first major investigation of myxomycetes in the soils of tropical forests.
"We know that myxomycetes are common organisms in soils, and there is increasing evidence that they are very important in such ecological processes as nutrient cycling," Stephenson said. "However, at this point we don't even know just what species of myxomycetes occur in soils, how much the assemblage of species present changes from place to place, and what factors are responsible for any changes that are observed. Laura is attempting to provide answers to these questions."
Walker is involved with the Global Eumycetozoan Project at the University of Arkansas, an effort to compile a global inventory of slime molds spearheaded by Stephenson and Fred Spiegel, both professors of biological sciences in the J. William Fulbright College of Arts and Sciences.
Walker traveled to Panama on a Smithsonian Tropical Research Institute short-term fellowship. The primary research station for the research institute is located on Barro Colorado Island, the largest forested island on the Panama Canal waterway, and part of the Barro Colorado Nature Monument. The research station is internationally recognized as a major center for studies of lowland tropical moist forests.
"Working in Panama was a really fantastic experience," said Walker, who collaborated with Allen Herre and Benjamin Turner, staff scientists for the research institute. "The best part of working on the island is the interactions with the other scientists. The island is one of the best known, well studied and most visited biological field stations in the world, so I had the opportunity to talk to scientists of all ages and experience levels. I established relationships that will likely develop into opportunities for collaboration."
Walker earned a master's degree in biology at Washington University in St. Louis in 2008 and entered the doctoral program at the U of A in 2010. She anticipates earning her doctorate in May 2014. She likes to find slime molds when she's hiking, especially on the Buffalo River in north Arkansas. But that means frequent stops along the trail to collect samples.
"There's a saying, 'A mycologist ruins every good hike,'" Walker said. "I'm looking for them all the time. They are anywhere where there is plant material. If I see a log that has just the right amount of decay, I can see where they are going to be. I stop and get down on my knees and say, 'I found one.'"
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