Foliage‐age mixing within balsam fir increases the fitness of a generalist caterpillar |
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Authors: | ROB JOHNS DAN T QUIRING RENÉE LAPOINTE CHRISTOPHER J LUCAROTTI |
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Institution: | 1. Natural Resources Canada, Canadian Forest Service– Atlantic Forestry Centre, Fredericton, New Brunswick, Canada;2. Population Ecology Group, Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, New Brunswick, Canada;3. Present address: Hokkaido Research Center, Forestry and Forest Products Research Institute, Toyohira Sapporo, Hokkaido, Japan.;4. Sylvar Technologies Inc., Fredericton, New Brunswick, Canada |
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Abstract: | 1. Manipulative field studies were carried out to evaluate the foliage age preference–performance relationship for an extreme generalist herbivore, the whitemarked tussock moth (Orygia leucostigma Smith) (Lepidoptera: Lymantriidae), within balsam fir Abies balsamea (L.) Mill]. 2. Field surveys indicated that early instar caterpillars fed almost exclusively on young (i.e. current‐year) foliage, whereas late instars caterpillars fed on both young and mature (i.e. 1‐ and 2‐year‐old) foliage. 3. Survival of early instar caterpillars was highest in treatments where current‐year and/or 1‐year old foliage were available, but decreased significantly on older foliage. In contrast, late instar caterpillars had the highest survival when allowed to feed on all age classes of foliage, whereas potential fecundity was highest for late instars that fed on young foliage. 4. Overall, caterpillars had 32–65% higher fitness when able to feed on all rather than just one age class of foliage. 5. These results support both the ‘complementary diet' hypothesis, which states that dietary mixing of different‐aged foliage can increase nutrient uptake and/or dilute harmful secondary plant chemicals, and the ‘ontogeny’ hypothesis, which attributes changes in diet to changes in the nutritional needs and/or tolerance to plant defences of juvenile insects as they develop. |
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Keywords: | Foliage quality foraging behaviour intra‐tree heterogeneity polyphagy whitemarked tussock moth |
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