Fig. 1.

Classification of interaction types based on the relationship between individual stressor effects (INV and GEC, shown as light- and medium-gray bars, respectively) and the predicted additive effect (the sum of the individual stressor effects, dark gray), for example, cases where both INV and GEC effects are in the same direction (A) and where INV and GEC effects are in different directions (B). Observed combined stressor (INV&GEC) effects falling within the 95% confidence interval around the predicted additive effect are classified as additive. Effects that differ from the predicted additive (INV+GEC) effect but fall within the range of the individual stressor effects and the control are classified as antagonistic, and those falling outside of this range are classified as synergistic. Antagonistic and synergistic effects are further classified as “+” if the effect is more positive (beneficial) or “−“ if the observed is more negative (detrimental) than the predicted additive effect. All measured responses in the meta-analysis were coded such that negative effects indicate detrimental outcomes.