Variation in Growth, Chemical Defense, and Herbivore Resistance in Scots Pine Provenances
1998
Manninen, A.-M. | Vuorinen, M. | Holopainen, J. K.
Variation in the growth, chemical defense, and susceptibility to monophagous and polyphagous sucking herbivores was assessed for four Scots pine (Pinus sylvestris) provenances in Petri dish and pot experiments. Seed provenances, Muonio (MU), Suomussalmi (SU), Korpilahti (KO), and Saaremaa (SA) represented a 1200-km N–S gradient. Scots pines from SU were least preferred as a host plant by pine-feeding aphids Schizolachnus pineti Fabr. and Eulachnus agilis, and in pot experiments, pines from SA were most preferred. S. pineti also produced the fewest nymphs on pines from SU. Polyphagous Lygus rugulipennis laid significantly fewer eggs on pines from MU provenance, which were smaller than seedlings from other provenances. The total and some individual terpene concentrations increased, while the total resin acid concentration decreased, towards the north. The absolute concentrations of total or individual terpenes and resin acids in the needles of unfavored SU plants did not differ significantly from the other provenances. Only the proportional quantity of dehydroabietic acid was higher in SU plants than in KO plants, and it correlated, together with sandaracopimaric acid, negatively with the number of S. pineti nymphs in the reproduction experiment. Conversely, absolute concentrations of some terpenes correlated negatively and some resin acids positively with the number of S. pineti nymphs. The length and weight of shoots decreased towards the north, adequately explaining the number of Lygus eggs and the final numbers of both aphids. The results suggest that seedling size is a better estimator of susceptibility of pine seedlings to both specialist and generalist sucking insects than relative or absolute concentrations of monoterpenes and resin acids.
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