Responses of multiple generations of Gastrophysa viridula, feeding on Rumex obtusifolius, to elevated CO₂

Abstract

Rumex obtusifolius plants and three generations of the tri‐voltine leaf beetle Gastrophysa viridula were simultaneously exposed to elevated CO2 (600 ppm) to determine its effect on plant quality and insect performance. This exposure resulted in a reduction in leaf nitrogen, an increase in the C/N ratio and lower concentrations of oxalate in the leaves than in ambient air (350 ppm). Despite these changes in food quality, the effect of elevated CO2 on larvae of Gastrophysa viridula over three generations was minimal. However, the effect of CO2 did differ slightly between the generations of the insect. For the first generation, the results obtained were different from many of the published results in that elevated CO2 had no measurable effects on performance, except that third instar larvae showed compensatory feeding. Food quality, including leaf nitrogen content, declined over time in material grown in both ambient and elevated CO2. The results obtained for the second generation were similar to the first except that first instar larvae showed reduced relative growth rate in elevated CO2. Development time from hatching to pupation decreased over each generation, probably as a result of increasing temperatures. Measurements of adult performance showed that fecundity at the end of the second generation was reduced relative to the first, in line with the reduction in food quality. In addition at the end of the second generation, but not at the end of the first generation, adult females in elevated CO2 laid 30% fewer eggs per day and the eggs laid were 15% lighter than those in ambient conditions. These lighter eggs, coupled with no effect of elevated CO2 on growth during the third generation, meant that the larvae were consistently smaller in elevated CO2 during this generation. These results offer further insights into the effect that elevated CO2 will have on insect herbivores and provide a more detailed basis for population predictions.

Gastrophysa viridula (Coleoptera: Chrysomelidae) and biocontrol of Rumex - a review

“…Effectiveness of G. viridula biocontrol depends on the level of food consumption and species abundance. Intensity of herbivory is proportionate to the quality of dock leaves (Renner 1970a) which decreases in the course of growing season with their age (Brooks and Whittaker 1998). Cutting and regrowth thus increases the nutritional value of host plants (Smith and Whittaker 1980a).…”

“…Rust infection influences the site of oviposition and decreases the number of deposited eggs and their hatching success (Hatcher et al 1994) while leaf ageing decreases female vigour and consequently also egg size and viability of resulting larvae (Brooks and Whittaker 1998). Intraspecific competition also sets limits to population size.…”

Influence of leaf chemistry of Lotus corniculatus (Fabaceae) on larval development of Polyommatus icarus (Lepidoptera, Lycaenidae): effects of elevated CO2 and plant genotype

“…While most previous studies consider moths (see Watt et al 1995; for reviews), butterflies or other insects are less often investigated (but see, e.g., Awmack, Harrington & Leather 1997;Hughes & Bazzaz 1997;Bezemer, Jones & Knight 1998;Brooks & Whittaker 1998;Smith & Jones 1998). Because the response of plants and insects to elevated CO 2 are extremely species-specific, and different insect feeding guilds show different responses , further studies, especially long-term investigations including host-selection behaviour under elevated CO 2 , and considering the genetic variation in natural populations for the CO 2 response, are still needed.…”

Stressing food plants by altering water availability affects grasshopper performance

“…Insect responses to changes in food plant quality include compensatory feeding (Fajer 1989, Docherty et al 1996, decreased growth rates (Fajer 1989, Traw et al 1996, Hättenschwiler and Schafellner 1999, reduced final body mass, prolonged developmental time (Goverde and Erhardt 2003), increased mortality (Fajer 1989), and reduced reproduction (Brooks andWhittaker 1998, Buse et al 1998). At the level of the individual, these responses may negatively influence reproductive output and, as a consequence, population dynamics of insect herbivores.…”