Abstract Detail

Ecological Section

Mincey, Katherine [1], McKenna, Mary [2], Irby, William [3].

Physical and elemental defenses of nickel hyperaccumulators and their effects on herbivory.

The “elemental defense hypothesis” formulated by Boyd & Martens (1998) suggests that metal hyperaccumulating plants have an advantage over other species in that they can deter herbivory because of the large heavy metal concentrations in their tissues. Alyssum murale Waldst. and Kit. (Brassicacae) is a nickel hyperaccumulator from the Mediterranean region which also has trichomes on their leaves that are likely to act as a physical deterrent to herbivory. Here we examined effectiveness of the physical and elemental defenses of Alyssum murale in reducing herbivory by specialist (Pieris rapae) and generalist (Vanessa cardui) lepidopteron herbivores. A comparative study of herbivore responses was done for A. murale grown in Ni-amended soil at four levels (0 ppm, 100 ppm, 500 ppm, 2000 ppm) and for a related non-accumulator species, Alyssum montanum that has trichomes but no elemental defenses. Choice experiments were set up to test larval response to (1) trichomes only, (2) nickel only at 4 levels and (3) combined trichomes and nickel. There was a significant difference in the food choice of Pieris rapae. Larva showed a strong preference for cotyledons (without trichomes) over true leaves (with trichomes), while nickel was not a strong deterrent. Vanessa cardui showed no preference for trichomes consuming cotyledons and true leaves at all nickel levels indiscriminately. A significant difference was found between nickel levels with both species preferring to eat those with lower nickel concentrations. We also assessed the fitness of specialist herbivore P. rapae during a no-choice study with nickel-accumulator Brassica juncea at the same four nickel levels. Looking at weight gain vs. diet, there was no significant difference at the three lowest levels of nickel. When compared with the highest level, there was a slight difference in growth and a large amount of mortality. Overall, these results suggest that elemental and physical defenses may combine to protect plants against herbivory and can have a negative impact on herbivores’ fitness.

Broader Impacts:

1 - Auburn University, Biological Sciences, 516 E Glenn Ave, 215, Auburn, AL, 36830, United States
2 - HOWARD UNIVERSITY, Biology Department, 415 College St. N.W., Washington, DC, 20059, USA
3 - Georgia Southern University, Biology Department, P.O. Box 8042, Statesboro, Ga, 30460, USA

Keywords:
Nickel
hyperaccumulator
elemental defense
herbivory.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:45 PM
Number: PEC004
Abstract ID:213
Candidate for Awards:None