|Cane, James - Jim|
Submitted to: South African Journal of Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/20/2001
Publication Date: 12/20/2001
Citation: DAVIS, M.A., BOYD, R.S., CANE, J.H. HOST-SWITCHING DOES NOT CIRCUMVENT THE NI-BASED DEFENSE OF THE NI STREPTANTHUS POLYGALOIDES (BRASSICACEAE). SOUTH AFRICAN JOURNAL OF SCIENCE. 2001. 37:p.554-557 Interpretive Summary: Some plants growing on selenium soils, which are rich in elemental nickel, deal with this phytotoxic metal by storing it in their tissues. Nickel-rich foliage is generally toxic to herbivorous insects, including caterpillars. There is evidence that if diets of young caterpillars are free of toxins, that they can later develop better on other kinds of ch hwith a nickel-hyperaccumulating plant, and found that early feeding experience does not improve a caterpillar's chances for survival on a plant defended by nickel in its tissues.
Technical Abstract: Elevated tissue concentrations of metals have been shown to defend metal-hyperaccumulating plants against both herbivores and pathogens. We examined the effects of host switching on growth and survival of a generalist herbivore. Specifically, we tested the hypothesis that early larval development on non-toxic hosts could improve caterpillar performance on high-Ni Streptanthus polygaloides, a Ni hyper-accumulator. Initial larval performance (weight gain) was lowest for insects switched to high-Ni hosts. Decreased initial larval performance was also noted for insects switched from lettuce to low-Ni plants, but these larvae recovered quickly. Original host identity (lettuce or low-Ni plants) did not affect subsequent larval performance. By day 8 of the feeding trials, all larvae switched to high-Ni hosts had died. We concluded that polyphagous caterpillars are unable to counter Ni-based defenses via host switching.