The datatset was collected from field survey, common garden experiments and lab experiments. All data analyses were performed in R 4.1.3 (R Development Core Team 2021) and SPSS 20.0 (IBM SPSS, Somers, NY, USA). The effects of re-association history (infested vs. uninfested; 0-, 9-, 13-, 17-year-reassociation) on insect bioassays (i.e., development time, weight, pepsin and trypsin enzyme activity of O. communa), plant assays including biomass ratio, MDA change rate and antioxidant capacity (DPPH and ABTS), and leaf chemical assays (concentrations of tannin, lignin, CGA, two individual flavonol derivates, nitrogen and carbon) were estimated using general linear mixed models (LMMs) in R, with reassociation history as a fixed factor and population (nested within reassociation history) as a random factor. For all these data, we also separately assessed correlations with the duration of re-association with the specialist natural enemy (the number of re-association years, i.e., 0, 9, 13, 17) at the individual level using Spearman correlation assays in SPSS 20.0. To analyze the correlation between insect traits (i.e., development time, weight, pepsin and trypsin enzyme activity of O. communa) and leaf defensive chemicals (i.e., tannin and lignin), we calculated the mean value of each index at the population level for each of the four re-association durations and used Pearson correlation assays in SPSS 20.0. The same procedure was followed for analyzing the correlation between drought stress tolerance and concentrations of leaf antioxidant chemicals. In addition, for the widely targeted metabolic data, principal component analysis (PCA) was performed using R to visualize the sample distributions.