PARENT SESSION
Oral Session # 60: Invasive Species V: Genetics; Chemical Cycling Effects.
Presiding: S Miao
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 204.
Root herbivory affects nitrogen uptake and secondary chemical production in the invasive plant, Centaurea maculsa.
Newingham, Beth*,1, Vivanco, Jorge2, BassiriRad, Hormoz3, Good, William4, Callaway, Ragan4, 1 US Geological Survey, Moab, UT, USA2 Colorado State University, Fort Collins, CO, USA3 University of Illinois at Chicago, Chicago, IL, USA4 University of Montana, Missoula, MT, USA
ABSTRACT- Centaurea maculosa is one of the most invasive plants in the northwestern United States. Previous research has shown that C. maculosa compensates for root herbivory by biological controls, which sometimes results in increased negative effects on native grasses. We investigated the effects of two root-boring biocontrol species on C. maculosa, and tested two mechanisms by which C. maculosa may increase its competitive ability. In neither experiment did herbivory affect the growth of C. maculosa. In our first experiment, we tested the hypothesis that C. maculosa increases nitrogen uptake after herbivory by Agapeta zoegana. In a 15N labelled experiment, we examined the effects of herbivory on the 15N content of the roots and shoots of C. maculosa. Root herbivory decreased 15N in roots, but did not affect 15N in shoots. Since root herbivory decreased 15N, this experiment indicates that nitrogen uptake is not responsible for the increased competitive ability of C. maculosa experiencing herbivory. Studies have shown that C. maculosa produces a secondary chemical, (-)-catechin, which has powerful allelopathic effects on other plant species. In a greenhouse experiment, we subjected C. maculosa to shoot herbivory by Trichoplusia ni or root herbivory by Cyphocleonus achates and measured the amount of (-)-catechin produced by C. maculosa. Shoot herbivory had no effect on (-)-catechin production; however, root herbivory increased (-)-catechin production four-fold compared to uneaten and shoot damaged plants. Similar results were demonstrated in C. maculosa plants transplanted outdoors. These results suggest that root herbivory may increase the allelopathic effects of C. maculosa, and suggest caution when using some insect species as biocontrols to control C. maculosa.
Key words: invasive, nitrogen, Centaurea, allelopathy