title: Interactive direct and plant-mediated effects of elevated atmospheric [CO2 ] and temperature on a eucalypt-feeding insect herbivore.
abstract: Understanding the direct and indirect effects of elevated [CO2 ] and temperature on insect herbivores and how these factors interact are essential to predict ecosystem-level responses to climate change scenarios. In three concurrent glasshouse experiments, we measured both the individual and interactive effects of elevated [CO2 ] and temperature on foliar quality. We also assessed the interactions between their direct and plant-mediated effects on the development of an insect herbivore of eucalypts. Eucalyptus tereticornis saplings were grown at ambient or elevated [CO2 ] (400 and 650 μmol mol(-1) respectively) and ambient or elevated ( + 4 °C) temperature for 10 months. Doratifera quadriguttata (Lepidoptera: Limacodidae) larvae were feeding directly on these trees, on their excised leaves in a separate glasshouse, or on excised field-grown leaves within the temperature and [CO2 ] controlled glasshouse. To allow insect gender to be determined and to ensure that any sex-specific developmental differences could be distinguished from treatment effects, insect development time and consumption were measured from egg hatch to pupation. No direct [CO2 ] effects on insects were observed. Elevated temperature accelerated larval development, but did not affect leaf consumption. Elevated [CO2 ] and temperature independently reduced foliar quality, slowing larval development and increasing consumption. Simultaneously increasing both [CO2 ] and temperature reduced these shifts in foliar quality, and negative effects on larval performance were subsequently ameliorated. Negative nutritional effects of elevated [CO2 ] and temperature were also independently outweighed by the direct positive effect of elevated temperature on larvae. Rising [CO2 ] and temperature are thus predicted to have interactive effects on foliar quality that affect eucalypt-feeding insects. However, the ecological consequences of these interactions will depend on the magnitude of concurrent temperature rise and its direct effects on insect physiology and feeding behaviour.
authors.affiliation: Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, Australia.
authors.forename: T J
authors.initials: TJ
authors.lastname: Murray
authors.forename: D S
authors.initials: DS
authors.lastname: Ellsworth
authors.forename: D T
authors.initials: DT
authors.lastname: Tissue
authors.forename: M
authors.initials: M
authors.lastname: Riegler
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D057231:Climate Change; D005052:Eucalyptus / Q000254:growth & development / Q000378:metabolism*; D005247:Feeding Behavior / Q000187:drug effects; D060434:Herbivory; D006358:Hot Temperature; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D009036:Moths / Q000254:growth & development / Q000378:metabolism*; D010063:Ovum / Q000254:growth & development / Q000378:metabolism; D018515:Plant Leaves / Q000254:growth & development; D011679:Pupa / Q000254:growth & development / Q000378:metabolism
chemical_list: D002245:Carbon Dioxide