1. School of Resource Management; Faculty of Land and Food Resources; Univ. of Melbourne; 500 Yarra Blvd. Richmond Victoria 3121 Australia
2. School of Life and Environmental Sciences, Deakin Univ.; P.O. Box 423 Warrnambool Victoria 3280 Australia
3. Institute of Applied Ecology; Chinese Academy of Sciences; Shenyang 110016 Liaoning Province PRC
4. Dep. of Primary Industries, Private Bag 15, Ferntree Gully Delivery Centre; Lysterfield South Victoria 3156 Australia
5. Primary Industries Research Victoria-Parkville Centre; Dep. of Primary Industries; P.O. Box 4166 Parkville Victoria 3052 Australia