PARENT SESSION
Contributed Oral Session 86: Herbivory: Genetic Variability in Insect - Plant Interactions
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal
Genetic variation in defensive traits of Brassica nigra interacts with generalist and specialist herbivores to alter competition between plant species.
Lankau, Richard*,1, 1 University of California - Davis, Davis, CA, 95616
ABSTRACT- Extensive genetic variation in plant defense traits has been documented in many systems. While much research has focused on the maintenance of this variation, less work has addressed the consequences of this variation for ecological interactions and community structure. Artificial selection was used to create extensive variation in two defense traits (glucosinolate concentration and trichome density) in Brassica nigra. Field observations of natural communities suggest that the effects of glucosinolates on herbivores are dependent on the composition of the neighboring plant communities. To test the effects of genetic variation in these traits on species interactions, I competed B. nigra individuals from the selected lines against con- or heterospecific neighbors, and manipulated the intensity of competition and the presence of generalist and specialist herbivores to ask whether 1) selection on defensive traits differs between treatments, and 2) the outcome of species interactions varies with the defensive status of the target plants. While generalists were deterred by high levels of the chemical defense, specialists were attracted by them. Therefore, highly defended genotypes were strong competitors against heterospecifics, which share only generalists, but not against conspecifics, which also share specialists. Understanding what role intraspecific variation may play in interspecific interactions is vital if we are to make accurate predictions about how communities will change as genetic diversity continues to decline.
Key words: glucosinolates, specialist herbivores, generalist herbivores, competition