Developmental changes in resistance to herbivory: implications for individuals and populations

M. J C Kearsley, Thomas G Whitham

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Abstract

The performance of 2 species of insects transferred onto different-aged trees of the same naturally occurring clones of narrowleaf cottonwood Populus angustifolia showed opposing and significant changes in host resistance as a function of tree age. The gall-forming aphid Pemphigus betae was 70 times as common on mature trees as on juvenile trees. This pattern is adaptive; survivorship on mature trees was 50% higher than on juvenile trees. The leaf-feeding beetle Chrysomela confluens exhibited opposite distribution on hosts, with densities 400 times as high on juvenile as on mature trees. This is also adaptive; larvae transferred to mature hosts had 50% lower survival and took 25% longer to reach adulthood than those transferred to juvenile trees. Distributions apparently result from the insects' preferences for different-aged hosts. Developmental changes in resistance and susceptibility of hosts are important components in determining the distribution of herbivores. A single plant can change rapidly in its resistance traits with age such that a 10-fold change in resistance can occur over a 2-yr period. As trees mature, increased and decreased resistances to different herbivores can produce nonoverlapping herbivore distributions that could be misinterpreted as being the result of competition. -from Authors

Original languageEnglish (US)
Pages (from-to)422-434
Number of pages13
JournalEcology
Volume70
Issue number2
StatePublished - 1989

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ASJC Scopus subject areas

  • Ecology

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