PARENT SESSION
Poster Session # 9: Herbivory.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Effects of competition on plant size and secondary chemistry in Plantago.
Barton, Kasey*,1, Bowers, M. Deane1, 1 Department of Ecology and Evolution, Boulder, CO
ABSTRACT- Plants experience multiple biotic interactions simultaneously, although most studies examine interactions in isolation. The goal of this study was to test the effects of competition, both interspecific and intraspecific, on the anti-herbivore defense in Plantago lanceolata and P. major. The experiment had a 2x3x2 factorial design in which the factors were focal species (2), neighbor species treatment (3), and harvest time (2). Each replicate consisted of a single plant of either P. lanceolata or P. major planted in the center of the pot (focal species) and surrounded by 4 individuals of either P. lanceolata or P. major, or surrounded by no neighbors (neighbor species treatment). Harvested shoots were dried, weighed, and analyzed for iridoid glycoside concentrations. Plants grown without neighbors were significantly larger than those with neighbors (F*2,170 = 103.60, p<0.0001). The two species differed in their competitive ability as neighbors: focal plants with P. major neighbors were, on average, significantly larger than those with P. lanceolata neighbors (F*1,170 = 8.18, p=0.0048). Focal plant species and harvest date were reliable predictors of iridoid glycoside concentrations. Plantago lanceolata had significantly higher concentrations of iridoid glycosides than P. major plants (F*1,141 = 78.68, p<0.0001). Iridoid glycoside concentrations were higher in plants harvested in week 10 than those harvested in week 7 (F*1,141 = 44.89, p<0.0001). Iridoid glycoside concentrations were not influenced by the presence of neighbors. These results are discussed in light of evidence that nutrient availability influences plant defensive chemistry.
Key words: secondary chemistry, herbivory, competition, Plantago