The effects of enriched CO2 atmospheres on plant-insect herbivore interactions: growth responses of larvae of the specialist butterfly, Junonia coenia (Lepidoptera: Nymphalidae)

Abstract

Little is known about the effects of enriched CO environments, which are anticipated to exist in the next century, on natural plant-insect herbivore interactions. To begin to understand such effects on insect growth and survival, I reared both early and penultimate instar larvae of the buckeye, Junonia coenia (Lepidoptera: Nymphalidae), on leaves from one of their major hostplants, plantain, Plantago lanceolata (Plantaginaceae), grown in either ambient (350 PPM) or high (700 PPM) CO atmospheres. Despite consuming more foliage, early instar larvae experienced reduced growth on high CO-grown compared to ambient CO-grown leaves. However, survivorship of early instar larvae was unaffected by the CO treatment. Larval weight gain was positively correlated with the nitrogen concentration of the plant material and consumption was negatively correlated with foliar nitrogen concentration, whereas neither larval weight gain nor consumption were significantly correlated with foliar water or allelochemical concentrations. In contrast, penultimate instar larvae had similar growth rates on ambient and high CO-grown leaves. Significantly higher consumption rates on high CO-grown plants enabled penultimate instar larvae to obtain similar amounts of nitrogen in both treatments. These larvae grew at similar rates on foliage from the two CO treatments, despite a reduced efficiency of conversion of ingested food (ECI) on the low nitrogen, high CO-grown plants. However, nitrogen utilization efficiencies (NUE) were unaffected by CO treatment. Again, for late instar larvae, consumption rates were negatively correlated with foliar nitrogen concentrations, and ECI was also very highly correlated with leaf nitrogen; foliar water or allelochemical concentrations did not affect either of these parameters. Differences in growth responses of early and late instar larvae to lower nitrogen, high-CO grown foliage may be due to the inability of early instar larvae to efficiently process the increased flow of food through the gut caused by additional consumption of high CO foliage.

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

“…Other studies similarly found no difference in larval survival under different CO 2 regimes (Osbrink, Trumble & Wagner 1987;Akey & Kimball 1989;Fajer 1989), though increased mortality under elevated CO 2 can be found when plant nitrogen is very low (Fajer, Bowers & Bazzaz 1989). Our larvae reared on plants grown under elevated CO 2 conditions were heavier in both early and final larval instars.…”

Direct effects of increasing carbon dioxide on pasture plants and communities

“…At the higher levels of CO 2 the larvae were required to consume a greater quantity of leaf in order to maintain sufficient N intake. A similar response has been shown by the larvae of Junonia coema (Lepidoptera: Nymphalidae) feeding on Plantago lanceolata (Fajer 1989). Fajer et al (1989) have suggested that a lower availability of quality food may be the major response to COz relevant to herbivorous insect larvae, and could result in smaller larvae, less capable of defending themselves, and in larvae which may find it difficult to complete their development when other conditions are unfavourable (Fajer 1989).…”

Interactive effects of multiple climate change variables on trophic interactions: a meta-analysis

“…As an example, consider the effects of the CO 2 × temperature interaction on a typical plant-herbivorous insect feeding relationship, which was the most commonly examined trophic relationship across the studies we analyzed. Plant quality from the perspective of herbivorous insects is generally determined by the nutrient profile of the plant (particularly the C:N ratio for nitrogen limited insects [59,60]), any defensive chemical compounds produced by the plant (e.g., phenolics and terpenes), and the physical traits of plant tissues (e.g., leaf toughness and thickness [22]). In general, plants raised in environments with high concentrations of CO 2 exhibit high C:N ratios, increased production of phenolics, and increased leaf toughness and thickness [21,22].…”