The effect of climate change on an aphid-coccinellid interaction

A model (Carter et al. 1982) that described the population dynamics of Sitobion avenae was modified and extended to include the population dynamics of the aphidophagous coccinellid, Coccinella septempunctata. The model was run under three different temperature regimes, corresponding to different degrees of warmth in typical English summers, and, in addition, within-regime temperature was altered, to predict the likely effects of climatic change on the interaction between the aphid and coccinellid. The model predicts that the presence of coccinellids causes a reduction in the number of aphids of between 40 and 60 percent, and advances the Julian date of their maximum numbers. The model also predicts that an increase in temperature within a regime results in smaller maximum and total numbers of aphids. In the presence of coccinellids, aphids were predicted to be most successful in moderately warm summers. The predicted maximum number of coccinellids was not greatly affected by temperature, but their total number was, in a complex way. The greatest effect of coccinellids to reduce both maximum and total aphid numbers was predicted to occur for relatively hot summers. A sensitivity analysis was used to identify those aspects of the coccinellid submodel that require possible refinement.