|
|
-
Coevolution
John Nason's desert plant research examines reciprocal evolution.
- Biologists view coevolution as a major player in the organization of the earth's biodiversity.
It's a topic that John Nason, associate professor in the Department of Ecology, Evolution and Organismal Biology, and his research team and colleagues have been studying in the Sonoran Desert in northwestern Mexico. Nason and a collaborator from Virginia Commonwealth University are using a three-year, $350,000 National Science Foundation grant awarded last year to support the research.
Coevolution is reciprocal evolution resulting from the interactions between species over a long period of time. As one species evolves, it spurs an evolutionary response in other species and vice versa.
For example, Nason explained that the larvae of butterflies that attack a certain plant species for food will evolve in response to evolution in the plant (which might develop defense chemicals) to ward off such an attack.
“A different type of example is a mutualistic interaction, in which interacting species benefit, such as when an insect pollinates a plant in exchange for nectar or other floral rewards.”
Nason added, “Coevolutionary interactions, ancient and ongoing, are found throughout nature and include the beneficial relationships between mitochondria and our cells, microbial symbionts and our digestive system, chloroplasts and plant cells, etcetera, as well as the antagonistic host-parasite and predator-prey relationships.
“The ubiquity of such relationships suggests that coevolutionary interactions between organisms have a big influence on how organisms evolved.”
For years biologists looked at the evolution of species independently of each other, focusing primarily on adaptations to physical features of the environment, such as temperature, rainfall and elevation. Now scientists realize that biological interactions also are important to organismal diversity.
“There's a lot of interest in coevolution, and it's spurring many new ways to look at things. It's a pretty exciting subject,” Nason added.
Nason's efforts involve the study of gene flow, the movement of genetic material from one population of a species to another. To illustrate, plant gene flow occurs when a grain of pollen or a seed is carried by the wind or an animal, successfully introducing genetic material into another population of the same plant species.
Specifically, Nason's current research focuses on developing methods to test for similarities or dissimilarities in geographical patterns of gene flow in coevolved plant-insect relationships. He is also investigating how patterns of gene flow influence coevolutionary outcomes between plants and insects.
He noted that coevolutionary interactions are highly dynamic, with changes taking place over time and in different geographical areas.
“We'll examine where, geographically, coevolutionary interactions are really dynamic - where coevolutionary hot and cold spots occur - and their relationship to patterns of gene flow,” Nason said.
Another part of his research examines the reproductive and genetic consequences of habitat fragmentation in wind- and animal-dispersed plant species.
Nason wants to gain important insight into the fundamental differences in gene flow dynamics in mutualistic versus host-parasite systems, differences that may influence the geographic patterning of coadaptation in plant-insect relationships.
The current NSF-supported project is using advances in statistical genetics and graphical modeling to create new analytical procedures for studying gene flow. Nason indicated his team benefits from combining quality genetic data analysis in the lab with a sound knowledge of a species' natural history in the field.
He said little research has been done on wild cotton, which has greater genetic variation than its valuable domestic cousin. “It could lead to a better understanding of the origins of important pests found on domesticated cotton.”
Around LAS
November 12 to December 2, 2007
|
|
