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Abstract

Using an experimental eucalypt forest of known pedigree and laboratory
feeding trials, we examined the relative importance of plant ontogeny (heteroblasty), genetic
variation among host trees, canopy height, and leaf age as potential drivers that could affect
the distribution and feeding preference of a common insect herbivore, Chrysophtharta
agricola. We found that ontogeny is a major factor affecting this insect. Its importance
rivaled leaf physiological age, a well-documented factor, which served as our standard for
judging the relative importance of other effects. Three patterns emerged: (1) In the field,
beetle feeding was nine times greater in the adult zone than in the juvenile zone of heteroblastic
trees (i.e., trees with both adult and juvenile foliage). (2) Laboratory feeding
trials confirmed their strong preference for adult foliage. (3) Although eucalypt species,
hybrid cross type (F1, F2, and backcrosses), and canopy height also exhibited significant
effects on beetle feeding in laboratory trials, their relative importance was much less than
ontogeny and leaf physiological age. We conclude that beetles perceive greater variation
in host quality within individual plants than between different eucalypt species and their
hybrids. The magnitude of these effects argues that ontogeny may rival other better studied
plant traits that affect herbivores. We discuss how genetic regulation of phenotypic expression
in plants may affect herbivore populations and structure communities.

Item Type:	Article
Authors/Creators:	Lawrence, R and Potts, BM and Whitham, TG
Keywords:	canopy height; Chrysophtharta agricola; common garden; chrysomelid; Eucalyptus globulus; Eucalyptus nitens; heteroblasty; hybridization; insect preference; ontogeny; physiological age; synthetic hybrids.
Journal or Publication Title:	Ecology
ISSN:	0012-9658
DOI / ID Number:	https://doi.org/10.1890/0012-9658(2003)084[1171:RIOPOH]2.0.CO;2
Additional Information:	BM Potts.
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