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Phenotypic variation in host quality of pines for the European pine sawfly (Neodiprion sertifer)

Chorbadjian, Rodrigo A.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1230736665

Abstract Details

2008, Doctor of Philosophy, Ohio State University, Entomology.
Phenotypic variation in host quality can affect ecological and evolutionary interactions between plants and herbivores. Effects of phenotypic variation in host quality of woody-plants on performance of leaf feeding insects were investigated in three studies: (1) phenological variation of Scots pine (Pinus sylvestris) needle quality for the European pine sawfly (Neodiprion sertifer) as a test of the "phenological window of host susceptibility hypothesis", (2) effects of fertilization on the expression of defoliation-induced resistance of Austrian pine (P. nigra) to European pine sawfly, and (3) manipulation of growth/defense trade-offs in paper birch (Betula papyrifera) and Austrian pine through application of the plant growth regulator paclobutrazol. Consistent with the predictions of the phenological window hypothesis, larval growth and survival decreased as host-insect synchronicity was modified. Foliar quality declined as current-year shoots and needles elongated, which suggests that larvae tolerate plant defenses only if nutrient concentrations are high relative to chemical defenses. A slow increase in host quality occurred late in the growing season as mature foliage once again became suitable. The survival of an experimentally-generated second generation of larvae manipulated to emerge in September was only 20% on current- or previous-year foliage; however survival was 80% the following spring. This phenological window of host susceptibility appears to constrain the evolution of a second generation. The expression of defoliation-induced responses of Austrian pine to European pine sawfly larvae varied with level of fertilization. In the nutrient-rich environment, previous defoliation improved host quality for European pine sawfly larvae, which may promote insect outbreaks through positive density dependent (Allee) effects on population growth. However in the low nutrient treatment, host quality rapidly decreased following defoliation, which is thought to generate negative density dependent effects on population growth, thus stabilizing population density. Austrian pines tolerated defoliation through compensatory growth responses, an effect that was independent of the fertilization level and that was evident two growing seasons after the defoliation event. Concentration of foliar monoterpenes strongly increased one year after the defoliation treatment across all fertility levels. These results are inconsistent with predictions of the carbon nutrient balance hypothesis, which proposes that physiological constraints prevent defoliation-induced accumulation of carbon-based secondary metabolites in evergreens. These results suggest that in nutrient-poor soils Austrian pines would express rapid induced resistance that would help limit outbreaks and thus defoliation, while compensatory growth responses would enhance competitive ability. Application of the plant growth regulator paclobutrazol slowed the growth of paper birch and Austrian pine with no effect on photosynthesis. Consistent with the predictions of the growth-differentiation balance hypothesis, application of paclobutrazol increased the concentration of tannins and resistance of paper birch to gypsy moth (Lymantria dispar) and whitemarked tussock moth (Orgyia leucostigma), but only in the second growing season following treatment. Conversely, paclobutrazol had no effect on defensive chemistry of Austrian pine or its resistance to European pine sawfly. Although it has been suggested that paclobutrazol generally enhances tree resistance to insects, it was found here that its effect on tree resistance to leaf-feeding insects was species-specific and time-sensitive.
Daniel A. Herms (Advisor)
Pierluigi Bonello (Committee Member)
Luis Cañas (Committee Member)
Larry Phelan (Committee Member)
169 p.
Entomology
Insect-plant interactions host quality secondary metabolites defense nutrients growth-defense trade-offs induced resistance susceptibility European pine sawfly soil fertility paclobutrazol

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Citations

  • Chorbadjian, R. A. (2008). Phenotypic variation in host quality of pines for the European pine sawfly (Neodiprion sertifer) [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1230736665

    APA Style (7th edition)

  • Chorbadjian, Rodrigo. Phenotypic variation in host quality of pines for the European pine sawfly (Neodiprion sertifer). 2008. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1230736665.

    MLA Style (8th edition)

  • Chorbadjian, Rodrigo. "Phenotypic variation in host quality of pines for the European pine sawfly (Neodiprion sertifer)." Doctoral dissertation, Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1230736665

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.