Effect of short-term high-temperature exposure on the life history parameters of Ophraella communa

Abstract

Extreme heat in summer is frequent in parts of China, and this likely affects the fitness of the beetle Ophraella communa, a biological control agent of invasive common ragweed. Here, we assessed the life history parameters of O. communa when its different developmental stages were exposed to high temperatures (40, 42 and 44 °C, with 28 °C as a control) for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage). The larval stage was the most sensitive stage, with the lowest survival rate under heat stress. Egg and pupal survival significantly decreased only at 44 °C, and these two stages showed relative heat tolerance, while the adult stage was the most tolerant stage, with the highest survival rates. High temperatures showed positive effects on the female proportion, but there was no stage-specific response. Treated adults showed the highest fecundity under heat stress and a similar adult lifespan to that in the control. High temperatures decreased the F₁ egg hatching rate, but the differences among stages were not significant. Negative carry-over effects of heat stress on subsequent stages and progenies' survival were also observed. Overall, heat effects depend on the temperature and life stage, and the adult stage was the most tolerant stage. Ophraella communa possesses a degree of heat tolerance that allows it to survive on hot days in summer.

Figure 1

Mean ± SE survival rate (%) of Ophraella communa after exposure of eggs (a) larvae (b) pupae (c) and adults (d) to high temperatures [28 (control), 40, 42 and 44 °C] for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage). Black columns represent the survival rate (%) of the individual treated stages, while white columns indicate the survival rate (%) over all relevant stages (or male adults). The sample sizes for each treatment with five replicates were (a) 2,000, (b) 1,800, (c) 1,100 and (d) 250 (125 males and females). Different upper-case letters indicate significant differences among temperatures for treated eggs, larvae, pupae, and female adults (Tukey’s HSD test, P < 0.05). Different lower-case letters indicate significant differences among temperatures for subsequent stages and male adults (Tukey’s HSD test, P < 0.05). *Indicates a significant difference between males and females within each temperature (Tukey’s HSD test, P < 0.05); ns, not significant.

Figure 2

Mean ± SE female proportion [F/(F + M)] (%) of Ophraella communa when eggs, larvae, and pupae were exposed to high temperatures [28 (control), 40, 42 and 44 °C] for 3 h each day for 3, 5, and 5 days, respectively (by stage). The sample sizes for each treatment with five replicates were 2,000 (eggs), 1,800 (larvae) and 1,100 (pupae). Different lower-case and upper-case letters indicate significant differences among temperatures for the same life stage and among life stages at the same temperature level, respectively (Tukey’s HSD test, P < 0.05).

Figure 3

Mean ± SE female fecundity (number of eggs per female) of Ophraella communa when eggs, larvae, pupae, and adults were exposed to high temperatures [28 (control), 40, 42 and 44 °C] for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage). The sample size for each treatment was 20 pairs, and each pair was treated as one replicate. Different lower-case and upper-case letters indicate significant differences among temperatures for the same life stage and among life stages at the same temperature, respectively (Tukey’s HSD test, P < 0.05).

Figure 4

Mean ± SE female adult longevity (days) of Ophraella communa when eggs, larvae, pupae, and adults were exposed to high temperatures [28 (control), 40, 42 and 44 °C] for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage). The sample size for each treatment was 20, and each individual was treated as one replicate. Different lower-case and upper-case letters indicate significant differences among temperatures for the same life stage and among life stages at the same temperature, respectively (Tukey’s HSD test, P < 0.05).

Figure 5

Mean ± SE male adult longevity (days) of Ophraella communa when eggs, larvae, pupae, and adults were exposed to high temperatures [28 (control), 40, 42 and 44 °C] for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage). The sample size for each treatment was 20, and each individual was treated as one replicate. Different lower-case and upper-case letters indicate significant differences among temperatures for the same life stage and among life stages at the same temperature, respectively (Tukey’s HSD test, P < 0.05).

Figure 6

Mean ± SE percent of the F₁ egg hatching rate of Ophraella communa when eggs, larvae, pupae, and adults were exposed to high temperatures [28 (control), 40, 42 and 44 °C] for 3 h each day for 3, 5, 5, and 5 days, respectively (by stage). The sample size for each treatment with five replicates was 1,600. Different lower-case and upper-case letters indicate significant differences among temperatures for the same life stage and among life stages at the same temperature, respectively (Tukey’s HSD test, P < 0.05).