The role of genetic and chemical variation of
Pinus sylvestris seedlings in influencing slug herbivory
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O'Reilly-Wapstra, JM and Iason, GR and Thoss, V, The role of genetic and chemical variation of
Pinus sylvestris seedlings in influencing slug herbivory, Oecologia, 1, (152) pp. 82-91. ISSN 0029-8549 (2007) [Refereed Article]
This study investigated the genetic and chemical basis of resistance of Pinus sylvestris seedlings to herbivory by a generalist mollusc, Arion ater. Using feeding trials with captive animals, we examined selective herbivory by A. ater of young P. sylvestris seedlings of different genotypes and correlated preferences with seedling monoterpene levels. We also investigated the feeding responses of A. ater to artificial diets laced with two monoterpenes, Î"3-carene and Î±-pinene. Logistic regression indicated that two factors were the best predictors of whether seedlings in the trial would be consumed. Individual slug variation (replicates) was the most significant factor in the model; however, Î±-pinene concentration (also representing Î²-pinene, Î"3-carene and total monoterpenes due to multicollinearity) of needles was also a significant factor. While A. ater did not select seedlings on the basis of family, seedlings not eaten were significantly higher in levels of Î±-pinene compared to seedlings that were consumed. We also demonstrated significant genetic variation in Î±-pinene concentration of seedlings between different families of P. sylvestris. Nitrogen and three morphological seedling characteristics (stem length, needle length and stem diameter) also showed significant genetic variation between P. sylvestris families. Artificial diets laced with high (5 mg g-1 dry matter) quantities of either Î"3-carene or Î±-pinene, were eaten significantly less than control diets with no added monoterpenes, supporting the results of the seedling feeding trial. This study demonstrates that A. ater selectively feed on P. sylvestris seedlings and that this selection is based, in part, on the monoterpene concentration of seedlings. These results, coupled with significant genetic variation in Î±-pinene concentration of seedlings and evidence that slug herbivory is detrimental to P. sylvestris fitness, are discussed as possible evidence for A. ater as a selective force on the evolution of defensive chemistry in P. sylvestris. Â© 2006 Springer-Verlag.
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