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Abstract:
The effect of herbivory on plant performance is
the subject of a large number of ecological studies, and
plant responses to herbivory range from reduced reproduction
to overcompensation. Because plant defenses,
stored resources, and allocation demands change throughout
a plant’s lifetime, it can be hypothesized the effects of
herbivory also vary with development. The present work
extends previous analyses to incorporate hundreds of
studies in a new meta-analysis addressing this topic. Herbivores
had an overall negative effect on plant growth and
reproduction, and, in contrast to a previous meta-analysis,
this work shows the timing of herbivory is relevant. Differences
in the effects of herbivory between life stages
existed for woody plant reproduction and perennial herb
growth. In addition, tree and shrub growth was reduced by
herbivore damage at early ontogenetic stages, and perennial
herb reproduction was limited by adult stage herbivory.
These results partially support the continuum of an
ontogenetic response model. Finally, consideration of this
synthesis in conjunction with other work led to the conclusion
that different plant groups optimize their defense
investments in unique ways. Slow-growing plants may
strongly chemically defend young tissues, supporting the
plant–age hypothesis, because early herbivory is detrimental
to growth. Faster-growing herbs may invest more in
antiherbivore defense when they are older, supporting the
growth–differentiation balance hypothesis, because later herbivory limits their reproduction.
