1. Department of Botany & Zoology Stellenbosch University Private Bag X1, Matieland 7602 Stellenbosch South Africa
2. Theoretical Ecology Group, Department of Mathematical Sciences Stellenbosch University Private Bag X1, Matieland 7602 Stellenbosch South Africa
3. Centre for Invasion Biology, Department of Botany and Zoology Stellenbosch University Private Bag X1, Matieland 7602 Stellenbosch South Africa
4. Theoretical and Physical Biosciences African Institute for Mathematical Sciences Cape Town 7945 South Africa
5. National Museum, Bloemfontein P.O. Box 266 Bloemfontein 9300 South Africa