1. Is the response of insect herbivores to elevated CO 2 and temperature universally predictable for different host tree species? Andrew Gherlenda Dr. Tony Haigh, Dr. Ben Moore, Dr. Scott Johnson, Dr. Markus Riegler

2. Impacts on insect herbivores Altered leaf chemistry at elevated CO 2 and temperature Species-specific responses to climate change Eucalypt foliage relatively nutrient poor Reduced foliar quality may; – Decrease survival, pupal weight – Increase developmental time Ainsworth & Rogers, 2007, GCB, Stiling & Cornelissen, 2007, GCB, Robinson et al., 2012, New Phytol

3. Immune response Encapsulation and melanisation via phenoloxidase (PO) cascade main defence against parasitoids and entomopathogens Activating an immune response is energetically expensive Smilanich et al., 2009, Ecology, Freitak et al., 2003, P Roy Soc Lond B Bio

4. Objectives Determine the effects of elevated CO 2, temperature and their interactions on herbivore performance Assess if insect response to eCO 2 and eT are consistent between different host plant species Assess whether the immune response of larvae was altered as a result of elevated CO 2 and temperature

5. Insect and host species Eucalyptus tereticornis Eucalyptus robusta Atlas of living Australia 2013 Paropsis atomaria (Coleoptera: Chrysomelidae) CAB International, 2005

6. Method Four CO 2 x temperature combinations – CO 2, 400 vs. 640 ppm – Temperature, 26:18 °C vs. 30:22 °C (15:9 hours) Larvae were placed onto trees (n=10) in a split brood design Expanding leaves analysed for foliar chemistry

7. Leaf quality decreases at eCO 2 E. robustaE. tereticornis CO 2 TemperatureInteractionCO 2 TemperatureInteraction Nitrogen n.s Phosphorous n.s C:N n.s TNC n.s

8. Survival increases at eCO 2 on E. robusta P = 0.045 P = 0.017 CO 2 P = 0.002 CO 2 P = 0.023

9. Longer developmental time at eCO 2 P = 0.044 CO 2 P <0.001 Temp P <0.001 CO 2 P <0.001 Temp P = 0.003

10. Decreased pupal weight at eCO 2 CO 2 P <0.001 CO 2 P = 0.003

11. Reduced insect performance Response fairly predictable across different hosts – Survival may improve on some host species at eCO 2 eCO 2 is main factor in reduced insect performance mediated by leaf chemistry – Temperature had limited effect – Compensatory feeding did not overcome reduced leaf quality

12. Immune response (defence) Eucalyptus tereticornis only Implanted with a nylon filament (2 mm long 0.25 mm diameter) Assay of: – Phenoloxidase (PO) activity – Haemolymph protein content – Encapsulation response (darkening of nylon filament)

13. Reduced E. tereticornis foliar traits CO 2 P <0.001 CO 2 P = 0.004 Temp P = 0.002

14. Immune traits PO activity Haemolymph protein Encapsulation response CO 2 Temperaturen.s

15. Immune traits P = 0.018P = 0.021 P = 0.030

16. Reduced defence at eCO 2 Insect herbivores may be more susceptible to attack at eCO 2 as a result of decreased PO activity – Encapsulation response may mediate this PO activity indirectly affected by foliar chemistry

17. Responses predictable? Elevated CO 2 reduces the growth and defence of larval insect herbivores mediated by reductions in plant nutrition – Reduced abundance in future?? In general, the response of herbivores to climate change is similar on different hosts – Localised benefits may occur Hamilton et al., 2012, Acta Oecol, Stiling et al., 1999, Ecol Appl

18. Acknowledgments Goran Lopaticki Aidan Hall James Ryalls Riegler’s lab group Hawkesbury Institute for the Environment CSIRO tree seed centre