Landmark Research Shows Genetic Link To Community Makeup And Ecosystem Evolution

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Landmark Research Shows Genetic Link To Community Makeup And

Ecosystem Evolution

http://www.medicalnewstoday.com/medicalnews.php?newsid=48006

It's common knowledge that genes control traits such as eye and hair

color. But a large group of scientists from two continents has found

that the genes of one organism not only control the characteristics

of that individual but also dictate the behavior of thousands of

other organisms in a community.

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 far-reaching implications. Consider, for example,

conservation efforts to preserve biodiversity in the face of habitat

destruction, climate change and other impacts on the environment.

Planting trees that are genetically diverse will result in increased

diversity of other species in the dependent community. The greater

the tree diversity, the greater the chance of associated species

surviving environmental degradation.

" It's not enough to save rare and endangered species. We need to save

genetic diversity in the foundation species, " said

Schweitzer, a co-author of the Nature Reviews Genetics paper and

postdoctoral researcher at NAU. " Having high genetic diversity in

these foundation species is insurance against changes in the future. "

The research also has ramifications when it comes to genetically

modified organisms and their effects on the landscapes in which they

are introduced. For example, grasses that are genetically altered to

prevent weed growth could pass that resistance along to exotic

plants, which then might take over a community and change the

evolution of that ecosystem.

More than 50 researchers from the United States, Canada and Australia

are studying this genetic driver of community structure and ecosystem

evolution. The work is funded by a $5 million Frontiers in

Integrative Biological Research grant from the National Science

Foundation. The project includes scientists from a multitude of

disciplines because, as Whitham says, " No one person has all the

skills to do this. "

" This is an exciting project with global impact, drawing on the

expertise of geneticists, ecologists, molecular biologists,

biogeographers and others, " said Greer, program director at the

National Science Foundation. " The results are expected to not only

shed light on how complex biological communities function but to

inform efforts to address the impact of human activities, such as

landscape fragmentation, on stressed ecosystems across the planet. "

The researchers are the first to study the genetic framework of

communities and ecosystems in the wild. They have planted several

experimental " common gardens " of cottonwoods in Arizona and Utah. The

trees are propagated at NAU's research greenhouse. Through DNA

fingerprinting, the scientists know the precise genetic makeup of

each tree.

In one experiment, Whitham's group worked with the Bureau of

Reclamation to plant about 10,000 trees at the Cibola National

Wildlife Refuge along the lower Colorado River, about 20 miles south

of Blythe, Calif., to examine how genetic diversity at the stand

level influences communities and ecosystem processes.

" The Bureau of Reclamation gets restoration out of this project, and

we get this incredible experiment, " said Whitham.

All of the experiments, so far, have exceeded the researchers'

expectations. " Initially we thought that the [genetic influences]

would be more localized--that the influences would be less genetic

and more environmental as we moved beyond the local common garden

setting to all of the western U.S. " In the end, however, Whitham

said, " Plant genes are far more important than we ever expected them

to be. "

Now the researchers want to know if their findings hold true in

different environments around the world. " To understand how important

something is, you have to test in multiple locations, " Whitham said.

A parallel study in Australia that examines the eucalyptus tree as

the foundation species is yielding the same results as the studies on

cottonwoods. And Whitham has just returned from South Africa and

Borneo in Southeast Asia, where he is planting the seeds for further

study.