Heat wave event facilitates defensive responses in invasive C3 plant Ambrosia artemisiifolia L. under elevated CO2 concentration to the detriment of Ophraella communa

Abstract

To predict and mitigate the effects of climate change on communities and ecosystems, the joint effects of extreme climatic events on species interactions need to be understood. Using the common ragweed (Ambrosia artemisiifolia L.)-leaf beetle (Ophraella communa) system, we investigated the effects of heat wave and elevated CO₂ on common ragweed growth, secondary metabolism, and the consequent impacts on the beetle. The results showed that elevated CO₂ and heat wave facilitated A. artemisiifolia growth; further, A. artemisiifolia accumulated large amounts of defensive secondary metabolites. Being fed on A. artemisiifolia grown under elevated CO₂ and heat wave conditions resulted in the poor performance of O. communa (high mortality, long development period, and low reproduction). Overall, under elevated CO₂, heat wave improved the defensive ability of A. artemisiifolia against herbivores. On the other hand, enhanced adaptability to climatic changes may aggravate invasive plant distribution, posing a challenge to the control of invasive plants in the future.

Keywords: Ophraella communa; biological invasions; climate change; common ragweed; herbivore; invasive plant; secondary metabolite.

Figure 1

Total phenolic concentration (±SE) of Ambrosia artemisiifolia under different stress conditions (n = 5). Data represented by columns bearing the same letters were not significantly different (LSD, p = 0.05). (A–E) Represent the first, second, third, fourth, and fifth measurements, respectively. AT denotes the ambient temperature condition; HW denotes the heat wave condition. EC and AC represent elevated atmosphere CO₂ concentration and ambient atmosphere CO₂ concentration, respectively.

Figure 2

Condensed tannins concentration (±SE) of Ambrosia artemisiifolia under different stress conditions (n = 5). Data represented by columns bearing the same letters were not significantly different (LSD, p = 0.05). (A–E) Represent the first, second, third, fourth, and fifth measurements, respectively. AT denotes the ambient temperature condition; HW denotes the heat wave condition. EC and AC represent elevated atmosphere CO₂ concentration and ambient atmosphere CO₂ concentration, respectively.

Figure 3

Effect on age-specific survivorship and fecundity of Ophraella communa after feeding on common ragweed grown under different treatment conditions. AT denotes the ambient temperature condition; HW denotes the heat wave condition. EC and AC represent elevated atmosphere CO₂ concentration and ambient atmosphere CO₂ concentration, respectively.

Figure 4

Effect on six enzyme activities of Ophraella communa after feeding on common ragweed grown under different treatment conditions. The green column denotes the female enzyme activity, the brown column denotes the male enzyme activity; AT denotes the ambient temperature condition; HW denotes the heat wave condition. EC and AC represent elevated atmosphere CO₂ concentration and ambient atmosphere CO₂ concentration, respectively; Different uppercase letters on the column indicate statistical differences between different genders, different lowercase letters on the column represent statistical differences between different treatment at P < 0.05, as determined by an ANOVA: LSD test.

Figure 5

(A) Volcano plot of differentially expressed metabolites; (B) statistics of Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. Leaves of plants under AC + AT and EC + HW conditions.