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Evolutionary biology: It's not just for textbooks anymore

UA scientists are on the leading edge of a new approach to tackle global challenges in food security, emerging diseases and biodiversity loss; Arizona's cotton crop provides evidence of their success

University of Arizona

Solving global challenges in food security, emerging diseases and biodiversity loss requires evolutionary thinking, argues a new study published online in Science Express that was co-authored by Bruce Tabashnik of the University of Arizona College of Agriculture and Life Sciences.

For the first time, an international team of nine scientists has reviewed progress in addressing a broad set of challenges in agriculture, medicine and environmental management using approaches that consider evolutionary histories and the likelihood of rapid adaptation to human activities.

The study finds an urgent need for better implementation of evolutionary approaches -- for example, to combat the problem of escalating resistance to antibiotics and pesticides. Furthermore, current efforts are found insufficient to reduce the accumulating costs from chronic disease and biodiversity loss, two crises ultimately caused by exposure to food and environments to which people and threatened wildlife are poorly adapted.

"Evolutionary principles provide insights for addressing some critical threats the world is facing now," said Tabashnik, who heads the UA's Department of Entomology and also is a member of the UA's BIO5 Institute. "An evolutionary perspective can give us effective new ways to deal with problems from agricultural pests, pathogens such as the Ebola virus, to cancer, antibiotic resistance and endangered species."

Tabashnik and his colleagues at UA have been at the forefront of research aiming to provide farmers with sustainable control of crop pests that reduces reliance on broad-spectrum insecticide sprays. An important advance in this effort is genetic engineering of cotton and corn to produce proteins derived from the widespread soil bacterium Bacillus thuringiensis, or Bt. Bt proteins kill certain insect pests but are harmless to most other creatures, including people. These environmentally friendly toxins have been used for decades in sprays by organic growers and since 1996 in engineered Bt crops by mainstream farmers.

Integration of Bt cotton plants with other tactics has revived Arizona's cotton industry, which was all but wiped out by invasive pest species. In particular, the refuge strategy based on evolutionary principles is credited with preventing resistance to Bt cotton by pink bollworm in Arizona for more than a decade.

Refuges consist of plants that do not have a Bt toxin gene and thus allow survival of insects that are susceptible to the toxin. Farmers plant refuges near Bt crops to produce enough susceptible insects to make it unlikely two resistant insects will mate and produce resistant offspring.

According to Tabashnik, the refuge strategy worked brilliantly against the pink bollworm in Arizona, where the pest had plagued cotton farmers for a century but is now scarce. In India, however, where farmers did not plant refuges, pink bollworm rapidly evolved resistance to Bt cotton.

"This particular success in Arizona can spur related evolutionary solutions in other regions and in other sectors," Tabashnik said.

According to the paper, the refuge strategy might even yield more effective cancer treatments. The idea is that portions of tumors with low vascularization and consequently low delivery of chemotherapeutic drugs may serve as refuges sustaining tumor cell lines that have not yet become resistant to chemotherapy.

"Compared with typical failures when oncologists try to eradicate a patient's cancer with high drug doses, lower doses could be more successful if they favor survival of chemosensitive cell lines that can outcompete chemoresistant lines," the authors write.

Other scientists at UA also are leaders in using evolutionary approaches to address global challenges. The research of Michael Worobey, a professor in the UA's Department of Ecology and Evolutionary Biology has produced breakthroughs in understanding AIDS, flu epidemics and obesity.

Researchers with the UA's Arizona Genomics Institute and the iPlant Cooperative have deciphered the genetic codes of crop plants, providing breeders with tools to produce varieties that have enhanced nutritional value and are better suited to cope with climate change. Most recently, an international research team led AGI Director Rod Wing sequenced the complete genome of African rice.

"Applying evolutionary biology has tremendous potential, because it takes into account how unwanted pests or pathogens may adapt rapidly to our interventions and how highly valued species including humans on the other hand are often very slow to adapt to changing environments through evolution," said study co-author Peter Søgaard Jørgensen, a biologist at the Center for Macroecology, Evolution and Climate at the University of Copenhagen. "Not considering such aspects may result in outcomes opposite of those desired, making the pests more resistant to our actions, humans more exposed to diseases and vulnerable species less able to cope with new conditions."

"To succeed in avoiding such unwanted outcomes, however, we need to learn from successes and progress in all fields using evolutionary biology as a tool. Currently there is no such coordination," said Scott P. Carroll, lead author and biologist at the University of California Davis and director of the Institute for Contemporary Evolution.

"Applied evolutionary biology uses principles common to all areas of biology, and because of this, progress in one area may often enable solutions in others," the paper concludes. "New approaches in this developing field may best be generated and assessed through collaborations that span disciplinary boundaries."

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Tabashnik's work on the paper was supported by the U.S. Department of Agriculture's Biotechnology Risk Assessment Grants Program.4

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