Prediction of the potential distribution of Carduus nutans (nodding thistle) in Australia

(1) The weed Carduus nutans spp. nutans has continued to spread in agricultural areas, since its introduction to Australia in 1950. Its present distribution is localized, mainly on the tablelands of New South Wales, and its potential distribution is unknown. (2) A model was developed to predict the growth, phenological development and seed yield of the weed, using commonly available climatic data from 286 climatic stations throughout Australia. The model was used to predict the potential distribution of C. nutans. Predicted seed yields were used to rank the stations, and hence areas of Australia, into four categories of potential infestation. (3) Regions in which C. nutans is known to occur, together with a number of presently uninfested regions, were predicted as being suitable for its growth and development. The validity of our predictions is discussed in relation to distribution of the species in Europe and other areas. (4) The limitations of the model and its possible usefulness in mapping weeds and studying weed biology are discussed.