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The Role of the Host Plant in the Population Dynamics of the Large Pine Aphid, Cinara pinea
Neil A. C. Kidd
Vol. 44, No. 1, Plant-Animal Interactions. Proceedings of the Third European Ecological Symposium. Lund, 22-26, August 1983 (Mar., 1985), pp. 114-122
Stable URL: http://www.jstor.org/stable/3544051
Page Count: 9
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A systems simulation approach was used to study the interactions between the large pine aphid, Cinara pinea, and its host tree, Pinus sylvestris. Seasonal changes within trees were found to have an important influence on growth, development, reproduction and mortality. In midsummer, after shoot expansion, aphids took longer to develop and had a lower chance of survival. They also grew more slowly into smaller, less fecund adults. Growth and development rates also varied from tree to tree. The interaction of these components with other aspects of the aphid/tree system are examined to provide a quantitative assessment of their relative contributions to observed changes in field population numbers. The peak aphid density shown by a tree in any year is determined partly by the density of eggs in the spring, which is itself influenced by predation the previous year. However, the peak number is also affected strongly by growth and mortality rates in the spring and early summer. While population density was found to influence growth and survival, its effects were found to be of secondary importance to those of the host plant. Tree-induced changes in nymphal growth and mortality were revealed to be the dominant factors, other than predation, limiting population growth in this species. It is concluded that variations in tree 'quality' from year to year and from tree to tree are of paramount importance in determining pine aphid population numbers. While shoot nitrogen levels correlate with aphid performance, it is argued, nevertheless, that tree quality may not just be a function of amino-nitrogen concentrations, or even of amino-acid quality or balance, but may be more a result of changing secondary plant chemistry or nutrient/allelochemic interactions.
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