Growth and Feeding Response of Pseudoplusia includens (Lepidoptera: Noctuidae) to Host Plants Grown in Controlled Carbon Dioxide Atmospheres

Abstract

1. Environmental change has the potential to influence trophic interactions by altering the defensive phenotype of prey. 2. Here, we examine the effects of a pervasive environmental change driver, elevated atmospheric concentrations of CO 2 (eCO 2), on toxin sequestration and flight morphology of a specialist herbivore. 3. We fed monarch butterfly larvae, Danaus plexippus, foliage from four milkweed, Asclepias, species of varying chemical defence profiles grown under either ambient or eCO 2. We also infected a subset of these herbivores with a protozoan parasite, Ophryocystis elektroscirrha, to understand how infection and environmental change combine to alter herbivore defences. We measured changes in phytochemistry induced by eCO 2 and assessed cardenolide, toxic steroid, sequestration and wing morphology of butterflies. 4. Monarchs compensated for lower plant cardenolide concentrations under eCO 2 by increasing cardenolide sequestration rate, maintaining similar cardenolide composition and concentrations in their wings under both CO 2 treatments. We suggest that these increases in sequestration rate are a by-product of compensatory feeding aimed at maintaining a nutritional target in response to declining dietary quality under eCO 2. 5. Monarch wings were more suitable for sustained flight (more elongated) when reared on plants grown under eCO 2 or when reared on Asclepias syriaca or Asclepias incarnata rather than on Asclepias curassavica or Asclepias speciosa. Parasite infection engendered wings less suitable for sustained flight (wings became rounder) on three of four milkweed species. Wing loading (associated with powered flight) was higher on A. syriaca than on other milkweeds, whereas wing density was lower on A. curassavica. Monarchs that fed on high cardenolide milkweed developed rounder, thinner wings, which are less efficient at gliding flight. 6. Ingesting foliage from milkweed high in cardenolides may provide protection from enemies through sequestration yet come at a cost to monarchs manifested as lower quality flight phenotypes: rounder, thinner wings with lower wing loading values.

Impacts of Climate Change on Lepidoptera Species and Communities

“…In these cases compensatory feeding is quite characteristic: larvae consume more (up to 25 % more) from the inferior food. Contradictory conclusions have been drawn from the studies: according to forestry trials, increasing atmospheric CO 2 content (ceteris paribus) can lead to decreased level of defoliation (Knepp et al, 2005), while others state that due to compensation feeding, the intensity of damages is expected to grow (Lincoln et al, 1984).…”

Adaptation and mitigation strategies in agriculture: an analysis of potential synergies

“…Elevated CO 2 may also indirectly modify insect-crop relations, via an increase in the C:N ratio in crop leaves, which renders them less nutritious per unit mass. This would stimulate increased feeding by insects, leading to more plant damage (Lincoln et al 1984;Salt et al 1995).…”

Predicting plant responses to global environmental change

“…The C: N ratio of leaves has also been shown to exert a marked effect on rates of herbivory, with rates increasing as the C:N ratio decreases, such as for leaves grown under COg enrichment (Lincoln et al, 1984(Lincoln et al, , 1986Fajer et al, 1989). Although the responses of the herbivores have been little studied so far, changes in population dynamics have been noted (Fajer, 1989;Fajer, Bowers & Bazzaz, 1989).…”