1. School of Mathematics and Physics; 2 CRC for Forestry; 3 School of Plant Science, University of Tasmania, Private Bag 55, Hobart 7001, Australia; 4 Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia; 5 Currency Creek Arboretum, P.O. Box 808, Melrose Park, South Australia 5039, Australia; 6 School of Computing Sciences, University of East Anglia, Norwich NR4 7TJ, UK