PARENT SESSION
Poster Session # 9: Herbivory.

Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Elemental defense of Streptanthus species against herbivores: A comparison of accumulated and hyperaccumulated levels of nickel.

Boyd, Robert¹, Jhee, Edward¹, ¹ Auburn University, Auburn, AL

ABSTRACT- Plants containing more than 1000 mg Ni/kg are considered nickel hyperaccumulators whereas those with lesser yet still elevated levels are nickel accumulators. Hyperaccumulated nickel may defend plants from herbivores, but the defensive role of lesser levels of metals is unknown. We raised five species of Streptanthus (Brassicaceae) native to serpentine soils, one of which is a hyperaccumulator (S. polygaloides) and the other four are accumulators, on Ni-amended and unamended greenhouse soils to create plants of differing Ni concentration. Slugs were fed plant material in no-choice tests over a 50-day period and slug survival and mass changes were recorded. All slugs fed high-Ni leaves of the hyperaccumulator species died within 21 days. Slugs fed high-Ni leaves of other plant species did not significantly differ in survival or mass change from those fed low-Ni leaves of those species. Choice tests using slugs offered both high- and low-Ni S. polygloides plants showed a strong preference for low-Ni plants. We conclude that hyperaccumulated Ni can defend S. polygaloides from herbivory via both toxicity and deterrence, but these defensive effects do not extend to Streptanthus species that simply accumulate Ni.

Key words: elemental defense, herbivore defense, hyperaccumulator, heavy metals