NICKEL HYPERACCUMULATED BY THLASPI-MONTANUM VAR MONTANUM IS ACUTELY TOXIC TO AN INSECT HERBIVORE

Some plants growing on serpentine soils sequester (hyperaccumulate) ni ckel from those soils in their tissues. Several ecological functions f or metal hyperaccumulation have been suggested, including defense agai nst herbivores. This study tests the herbivore defense hypothesis usin g the Ni hyperaccumulator Thlaspi montanum var. montanum. Leaves diffe ring 167-fold in Ni content (3,000 vs 18 ppm) were obtained by growing plants on high- and low-Ni soils. Leaves were fed to larvae of Pieris rapae, a generalist folivore. Larvae fed high-Ni leaves did not grow and suffered 100% mortality after 12 d, whereas those fed low-Ni leave s quadrupled in weight with a corresponding mortality of only 21%. Lar vae fed an artificial diet containing 0, 100, 500, or 1,000 ppm Ni sho wed acute toxicity at 1,000 ppm. We conclude that hyperaccumulated Ni can poison folivores that feed exclusively upon Ni-hyperaccumulating s pecies and therefore is an herbivore defense for some plants native to serpentine soils.