Selecting biological control agents

Predicting direct non-target impacts

Modelling non-target impacts

Climate matching

Climate matching has been widely used to predict the potential distributions of introduced plants and arthropods under current and future climates (Kriticos and Randall 2001). For example, CLIMEX software (Sutherst and Maywald 1985, Sutherst et al. 2007) empirically fits an eco-climatic envelope to the native distribution of a species and uses this to predict its potential introduced range. However, it is not clear how the relative ecoclimatic suitabilities of an area for a BCA and its target and nontarget hosts may affect the likelihood of impacts on each host. In the absence of data, some preliminary hypotheses were erected and explored using the case study system of an introduced BCA, the herbivorous weevil Cleopus japonicus, its target host plant Buddleja davidii and a known nontarget host plant Scrophularia auriculata. The hypotheses were: (1) impacts of the BCA on the target host plant are greatest in areas which are climatically optimal for the BCA but marginal for the plant, and (2) impacts of the BCA on the nontarget plant are greatest in areas which are marginal both for the target plant and the nontarget plant, but optimal for the BCA.

CLIMEX models were developed for C. japonicus and B. davidii in New Zealand, and the intent was to set up field experiments in localities with different climates to test the above hypotheses. However, the predicted potential distributions for both species were found to be very similar, making this a poor system for testing the hypotheses. Further work using other case studies may advance these ideas and eventually lead to a new tool for identifying where target and nontarget impacts are likely to be the greatest. This knowledge would help to design release, monitoring and management programmes for future BCA introductions.

References

Kriticos D.J. and Randall R.P. (2001). A comparison of systems to analyse potential weed distributions. Pp. 61-79 in: Groves R.H., Panetta F.D. and Virtue J.G. ed. Weed Risk Assessment. CSIRO Publishing, Melbourne, Australia.

Sutherst R.W. and Maywald G.F. (1985). A computerised system for matching climates in ecology. Agriculture, Ecosystems and Environment 13: 281-299.

Sutherst R.W., Maywald G.F. and Kriticos D.J. (2007). CLIMEX version 3. CD and User's Guide. Hearne Scientific Software, Melbourne, Australia.