CO2 improves the performance of an invasive insect: a worrisome climate crisis scenario to native and agricultural ecosystems

Abstract

Carbon dioxide (CO2) emissions are central in the Climate Crisis (CC) phenomenon, whose consequences indiscriminately affect natural and anthropogenic ecosystems. Among ecological interactions, plant-insect is one of the most impacted by the increase in [CO2]. In this study we tested the hypothesis that increased [CO2 ] would affect the host species Helianthus annuus leaf quality and defenses; in turn, this would negatively impact the preference and performance of Helicoverpa armigera larvae, an invasive insect currently distributed worldwide. Helianthus annuus and H. armigera developed inside open-top chambers under ambient (~400ppm) and increased [CO2] (~800ppm). Our predictions concerning sunflower development were mostly met, despite the acclimation, which eliminated the early differences in leaf nitrogen (N) and flavonoids (Flv) content. Sunflowers under increased [CO 2] grew more (e.g. height, leaf biomass, number of leaves) but were of poorer quality, especially at early development/before acclimation. Despite showing no preference for either treatment, H. armigera larvae performed better within a shorter developmental time when reared with leaves from increased [CO 2]: e.g. higher growth rate and greater proportion of pupae (3x) and adults (4x). Even after the acclimation effects (by the 11th week), H. armigera larvae under treated conditions maintained a greater consumption. This behavioral overcompensation was possibly due to the disadvantageous conditions that larvae under increased [CO 2] were submitted during their earliest/critical developmental stages (before acclimation). By consuming more relatively more plant material, these larvae were able to access a greater N accumulation, which increased with plant biomass. The improvement in H. armigera larvae performance under increased [CO 2] suggests an aggravated CC scenario. Specifically, an invasive species that already exerts great impact to native and agricultural ecosystems would be favored with an increased consumption and a population increase.