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KNOXVILLE — Research by University of Tennessee graduate student Gregory Crutsinger has shed light on a level of biodiversity that could influence the way plants are grown and seeds are sown.

Research has shown for some time that when different species of plants are grown together, it increases the overall productivity of their ecosystem, as well as leading to a more diverse community associated with the plants.

Crutsinger is a student in UT’s Department of Ecology and Evolutionary Biology.

His research, published in this week’s issue of the journal Science, looked at the same qualities on a different scale by examining the effect of using plants — in this case, goldenrod — of the same species, but with different genetic types. An example from agriculture would be an apple orchard growing Fuji, Granny Smith and Red Delicious side-by-side.

“Greg was able to show, with a novel experiment, that many ecologists have overlooked the diversity within species,” said Nathan Sanders, the UT professor who oversees Crutsinger’s work. “That could be key to understanding how ecosystems work, and just as importantly, how to put them back together again after disturbance.”

The results showed that increasing the genetic diversity can have just as much influence, if not more, than species diversity on both the plant production and the diversity of the insects in the area. This could have implications in a number of fields, from conservation to agriculture.

One key discovery in Crutsinger’s anaylsis was that the increased growth from mixed genotypes was not additive; that is to say, when multiple genotypes were grown in a plot together, they produced more biomass and maintained more insects than the sum of their individual genotypes grown separately. Biomass describes the weight of the part of the plant above the ground.

“This adds to the idea that diversity begets diversity,” said Crutsinger. “When you mix these different genetic types, a patch of plants can be more than the sum of its parts.”

Crutsinger began with 21 different genotypes of goldenrod, a number which reflects the local diversity of the species in the area. He grew each of the genotypes individually, as well as combining them in mixtures of three, six and 12 genotypes in a plot.

As the number of genotypes grown in a plot increased, the plots produced more biomass and the plots were home to more insects and a wider variety of insects.

The land for the research, located on the Freels Bend area of the Oak Ridge National Laboratory reservation, was provided by ORNL and the U.S. Department of Energy.

He chose goldenrod because it is a dominant plant in old-field ecosystems, growing from Florida up to Canada. It also features significant genetic diversity, and is a food source for a wide variety of herbivores.

Crutsinger made his first plantings in April 2005, measuring their growth and insect abundance through October of the same year.

“It was a lot of physical labor,” said Crutsinger, who built a rain collection and irrigation system on the land to ensure that the plants received the proper amount of water.

Sanders also noted the significance of Crutsinger’s research and his publication in Science at such an early stage in his career.

“What’s even more amazing about this work is that Greg did it during his very first summer in grad school,” said Sanders. “That’s unheard of.”

The next step in Crutsinger’s research will be to expand the scope of his work to study how genetics influence the way in which nutrients are cycled through the ecosystem.

Crutsinger, a Findlay, Ohio, native, earned his bachelor’s degree from Humboldt State University.


Jay Mayfield (865-974-9409, jay.mayfield@tennessee.edu)