Insect-host phenological synchrony: foliar terpenes and free amino acids in relation to European pine sawfly life cycle

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Plants are consumed by some insects only at specific periods of the season. Although pine trees hold their foliage all year, the European pine sawfly, a destructive insect pest of pine, only feeds during a narrow “window” of time in early spring. We tested the hypothesis that the life cycle of European pine sawfly is constrained to a narrow temporal window in early spring by phenological changes in plant quality that result in a limited period of host suitability. Consistent with the predictions of the phenological window hypothesis, larval growth and survival decreased as host-insect synchronicity was modified. As pine phenology advanced, foliar concentration of nutrients (free amino acids) decreased, and the strength of pine defenses did not relax (equal or higher level of terpenes). Strong correlations between foliar concentration of free amino acids and insect growth, consumption rate, and efficiency of conversion of ingested food, provided new evidence for their role in the nutritional ecology of the European pine sawfly.



plant defenses, Scots pine, Neodiprion sertifer, European pine sawfly, Pinus sylvestris, insect nutrition, terpenes, amino acids, phenology, synchrony, ecology, life-history