PARENT SESSION
Oral Session # 89: Insect Ecology II.
Presiding: R Sears
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 101.
Hyperaccumulated Ni defends Streptanthus polygaloides (Brassicaceae) against Plutella xylostella (Leptidoptera).
Jhee, Edward*,1, Boyd, Robert1, Eubanks, Micky2, 1 Auburn University, Auburn University, AL, USA2 Auburn University, Auburn University, AL, USA
ABSTRACT- Nickel hyperaccumulating plants contain more than 1000 mg Ni kg-1 dry mass when grown on Ni-amended soils. We hypothesized that Ni hyperaccumulated by Streptanthus polygaloides serves as an elemental defense against the Diamondback Moth, Plutella xylostella by deterring oviposition. An oviposition experiment used 2 X 5 arrays of S. polygaloides grown on Ni-amended (high-Ni) soil interspersed with plants grown on unamended soil (low-Ni). Diamondback Moths exhibited a significant oviposition preference for low-Ni plants. Moths allowed to oviposit on aluminum foil sheets dipped in extracts of hi-Ni or low-Ni plants significantly preferred low-Ni extracts. To determine if Ni was the factor influencing oviposition preference, we allowed moths to oviposit on foil sheets coated with low-Ni plant extract to which varying amounts of Ni were added. No difference in oviposition was observed, suggesting that factors other than Ni influence oviposition preference. Previous research has shown that hyperaccumulating S. polygaloides plants have a lesser concentration of glucosinolates. This trade-off might influence oviposition by an oligophagous herbivore since glucosinolates stimulate oviposition and feeding by Lepidopteran specialists on members of the Brassicaceae. To contrast fitness of high- and low-Ni plants, eggs were allowed to hatch and larvae feed freely among plants in the arrays. High-Ni plants had significantly greater biomass as measured by change in number of leaves and plant height. Reproductive effort (number of flowers) was also significantly greater for high-Ni plants. Ni hyperaccumulation may be an effective plant elemental defense against an oligophagous herbivore. By hyperaccumulating Ni, fitness of S. polygaloides is increased by toxicity to P. xylostella caterpillars and by decreasing oviposition by adults.
Key words: oviposition, hyperaccumulation, herbivory, plant animal interaction