Elevated CO₂ affects interspecific competition between the invasive thrips Frankliniella occidentalis and native thrips species

We explored the effects of elevated CO₂ on the population performance and interspecific interactions of three thrips pests. The dominance of the three thrips in the field was Frankliniella occidentalis ≈ Frankliniella intonsa > Thrips hawaiiensis. The performance of these thrips, alone and in combination, was evaluated in the laboratory under elevated CO₂ (800 μl L⁻¹) and ambient CO₂. Compared with ambient CO₂, elevated CO₂ significantly accelerated the developmental rates and decreased the survival rates of all thrips species. Significant differences in fecundity, intrinsic rate of increase (r_m), and net reproductive rate (R₀) were observed among these thrips, and their values were significantly increased in F. occidentalis but decreased in F. intonsa and T. hawaiiensis under elevated CO₂, compared that in the ambient CO₂ treatments. In treatments where thrips species coexisted, F. occidentalis and F. intonsa accounted for similar proportions of the population, and both were dominant over T. hawaiiensis within 10 generations under ambient CO₂. Under elevated CO₂, F. occidentalis was the dominant species and completely displaced F. intonsa and T. hawaiiensis by the ninth or eighth generation. Where the three species coexisted, no displacement occurred within 10 generations, but the pattern of dominance shifted to F. occidentalis > F. intonsa > T. hawaiiensis. Our results show that the population development of F. occidentalis benefits from elevated CO₂ and that it can become the dominant species in interspecific interactions with native thrips species. Thus, compared with native thrips species, F. occidentalis has greater adaptability and competitive capacity under elevated CO₂, and it may become a more dangerous crop pest under environmental change in the future.