It's all in the genes: These genes may, in fact, influence the evolution of an entire ecosystem. "We're pushing a whole new field of research," says lead investigator Tom Whitham of the biological sciences department. "The question we're asking is, does genetic variation mean anything at the community and ecosystem level?" More than 30 researchers from the United States, Canada and Australia will answer that question with the help of a five-year, $5 million Frontiers in Integrative Biological Research grant from the National Science Foundation. The project involves several disciplines-from ecology and soils to microbiology and molecular genetics-and includes extensive graduate and undergraduate student training. "Tom Whitham wanted to bring a genetics perspective into community biology," said Stephen Shuster, an NAU co-researcher who is interested in exploring quantitative genetics at the community level. "That's a concept that's kind of controversial. The traditionally held belief is that communities are assemblages of organisms, not evolved units. This research suggests that communities are not necessarily static assemblages, but are highly dynamic systems." Some of the genes under study are those that control the level of tannins in cottonwoods, which are dominant trees in riparian habitats in the West. Different individuals, or genotypes, of cottonwoods have different levels of tannins, the substances that give wine an oak flavor. Jen Schweitzer, an ecosystems ecologist on the team, has found that the concentration of tannins in a tree affects the decomposition rate of cottonwood leaves, which in turn affects the nitrogen content in soils, which affects the microbes in the soil, which affects the insects that live in the soil or that eat the leaves, which affects the birds that feed on the insects. NAU graduate student Carri LeRoy has determined that these same types of effects spill over to streams to impact the aquatic community. "This study has enormous conservation implications," said Kitty Gehring, another NAU member of the research team. "When we talk about conservation, we typically look at the species level. We need to look below the level of the species to the genetic level," said Gehring, who studies the mutually dependent relationship of fungi and the plant roots on which they live. Take, for example, genetically engineered foods, such as corn and soybeans. Attention focuses on potential risks for humans who ingest these foods, but what if the leaves from these modified plants affect the microbes in the soil differently? "This question should come under much closer scrutiny than just the corn and the people who eat the corn," Whitham said. He also points to grasses that are genetically altered to resist weed growth. If that genetic resistance were passed on to exotic plants, it would have far-reaching implications for the community and ecosystem. Researchers will plant several large-scale experimental cottonwood forests in which the genetic diversity of the trees ranges from high to low so they can study how genetic variation in a dominant tree affects the rest of the community. "No one has ever attempted this type of study in the wild," Whitham said. These experimental forests will have a side benefit. The planting of the cottonwoods also will help restore a riparian habitat at the Cibola Wildlife Refuge along the lower Colorado River, about 20 miles south of Blythe, Calif. The trees will be propagated at NAU's research greenhouse. Through DNA fingerprinting, scientists know the precise genetic makeup of each tree-more than 10,000 in all. The cottonwood tree is the first tree genome to be sequenced, providing the genetic background necessary for these studies. The researchers will track whether specific cottonwood genotypes spawn different community compositions. "The expectation is that we'll see changes in communities in predictable ways," Shuster said. But beyond that, the researchers anticipate they'll be able to show that the communities of organisms these trees support is a trait that is passed along to their offspring. That is, the progeny of a tree are likely to support the same communities of organisms that their parents supported. |
