1. School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
2. Present address: Department of Forest Science, University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada V6T1Z4
3. Present address: Centre for Reproduction and Genomics, Department of Anatomy and Structural Biology, University of Otago, PO Box 913, Dunedin 9054, New Zealand