Scriber, J.M., K. Weir, D. Parry, J. Deering
Presented at the All Scientist Meeting (1998-07-21 to 1998-07-22 )
Sub-plots of hybrid poplars in the Long Term Ecological Study site for “Agroecology” at the Kellogg Biological Station were experimentally defoliated using 10 million gypsy moth larvae. Half of the defoliated (and undefoliated control) plots were fertilized to see if this would ameliorate the predicted induction of carbon-based phenolic defenses in the regrowth of leaves. In order to bioassay the leaves of the four different treatments, we employed a continuum of genotypes (different hybrids and backcrosses of two different species of tiger swallowtail butterflies) with different abilities to detoxify these allelochemicals. Based on our previous studies with phytochemicals from the Salicaceae plant family, Papilio canadensis was likely to consume and process all Populus spp treatments, whereas P. glaucus predicted to either not consume or else quickly die on all Populus treatment leaves. Hybrid and backcross larvae of these two butterfly species are known to have intermediate levels of esterase detoxication enzymes and would therefore be likely to provide a continuum or at least varying degrees of sensitivity in bioassays for even the most subtle induction responses in the regrowth leaves. This presumption was supported in the feeding and growth studies conducted at different times post-defoliation during the 1997 growing season in Michigan.Fig 1. The relative growth rates mg · mg-1 · d-1) of penultimate instar P. canadensis fed hybrid Populus from four experimental treatments (+ with defoliation, + with fertilization, ets.)Fig 2. The relative growth rats of penultimate instar hybrid larvae (P. canandesis female X P. glaucus male) fed four Populus treatments.Return to Contents
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