Understanding intraspecific variation in plant defense across resource gradients

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Plants defend themselves from hungry animals by putting poisons in their leaves and thorns on their branches. There are many other ways they protect themselves, too. Ecologists have wondered for a long time why different species of plants adopt very different strategies of protection. Why wouldn't there be one best way? Even different individuals of the same species defend themselves differently. Thus, a major challenge in ecology is to figure out the causes and consequences of differences in plant defense. One idea is that plants in places where they can't grow fast, can invest more energy in defense. In contrast, plants in places with lots of water and nutrients can grow and reproduce quickly -- life is good, so they don't need as much defense. Scientists with this project will test that idea. They will look at how different individuals of the same species may change their strategies of defense when grown in stressful areas and areas of plenty. They will test how well the defenses work by measuring how tasty the plants are to insects. Results may reveal new strategies for protection of farm crops from insect pests. The researchers will involve high school and college students in the project, training them how to do science. Also, the public will be engaged through various natural history and conservation programs.This project involves reciprocally transplanting six co-occurring native grassland plant species from populations replicated within eight high- and eight low-resource environments into common gardens located in each region. Resources (rainfall) will also be manipulated in a common garden located in the low-resource region to evaluate the extent to which responses of plant growth and defense to abiotic factors are plastic. Herbivore abundance and the impacts of herbivores on plant fitness (accessed via insect-reduction experiments) will be quantified within populations containing the focal species across the two resource regions. Collectively, these experiments will evaluate how the resource environment influences: 1) growth and defense (both tolerance and resistance) evolution and plasticity within species; 2) positive growth and defense correlations across populations, and 3) insect herbivore abundance and the impacts of herbivory on plant fitness. Ultimately, the multispecies approach employed will help to reconcile the different growth-defense relationships often observed among vs. within species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.