They say these genes, in fact, influence the evolution of an entire ecosystem.

"We're pushing a whole new field of research," said lead investigator Tom Whitham, Regents Professor of biological sciences at Northern Arizona University.

It's a field that has not been explored before. After all, the idea of looking at the genes of thousands of species in even a simple community is daunting at best.

"What we've done is zero in on a foundation species, because not all species are as equally important ecologically," Whitham said. The foundation, or key, species in this case is the cottonwood tree, which is the first tree to have all its genes sequenced, or mapped.

Among 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.

These genetically controlled tannin levels drive the structure--or phenotype--of a riparian forest, according to Whitham. Tannins affect the decomposition rate of cottonwood leaves, which in turn affects the fertility of soils, which affects the microbes in the soil, which affect the insects that live in the soil or eat the leaves, which affect the birds that feed on the insects, and so on.

In the July issue of Nature Reviews Genetics and the May issue of Evolution, Whitham and fellow researchers discuss how this phenotype is heritable on an ecosystem level. That is, the progeny of a tree are likely to support the same communities of organisms and ecosystem processes that their parents supported.

It's a premise with fa
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Contact: Tom Bauer
Thomas.Bauer@nau.edu
928-225-0446
Northern Arizona University
24-Jul-2006