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The potential distribution of Chromolaena odorata (Siam weed) in relation to climate


D J Kriticos, Forest Research, PB 3020, Rotorua, New Zealand 3201. Tel: (+64) 7 343 5524; Fax: (+64) 7 343 5333; E-mail:


A climate model of the estimated potential distribution of Chromolaena odorata has been revised. The new model fits the known distribution better, eliminates several internal inconsistencies, and employs more biologically appropriate cold-stress mechanisms. The revised model reduces the estimated potential distribution of C. odorata, particularly in terms of the poleward and inland extents of suitable climates. Mediterranean, semi-arid and temperate climates are now predicted to be unsuitable. However, the revised model supports the previous conclusions that much of tropical Africa, the north-eastern coast of Australia and most Pacific islands are at risk of invasion. The distribution of C. odorata in South Africa extends further south than predicted by the model based on Asian and American distribution records. This anomaly supports the contention that the South African variety of C. odorata has different climatic requirements to the varieties commonly found elsewhere.