Ph.D. in Biochemistry and Microbiology Lincoln University, Canterbury, New Zealand. 1994.

Bachelor of Horticultural Science with First Class Honours gained at Lincoln University. 1990

Diploma in Horticulture gained at Lincoln College. 1985.

Research Interests:

The main focus of my research has been in the study of phylogenetic relationships for a range of organisms, but especially plants (e.g., Araliaceae and Brassicaceae). My work has involved the creation of morphological and molecular data bases for phylogenetic analyses of Pseudopanax species and related genera in the Araliaceae. Results suggested Pseudopanax is polyphyletic and indicated the presence two main lineages within the genus. I was able to expand my study by generating morphological and molecular data bases for Gingidia species and related genera in the Apiaceae. My work on the Araliaceae and Apiaceae resulted some intriguing questions regarding the relationships of the megaherb Stilbocarpa. I generated a molecular data base for Stilbocarpa and representatives for the Araliaceae and the three Apiaceae subfamilies and conducted parsimony and maximum likelihood analyses to determine their evolutionary relationships. Results suggest that Stilbocarpa, a taxon traditionally considered a herbaceous araliad, is most closely related to species from the Apiaceae subfamily Hydrocotyloideae. Repeated observation of closely related species groups within the New Zealand has lead me to become interested in questions to do with the application of species concepts and the study of relationships between closely related species complexes and populations of species. My research has begun to include more infraspecific studies, e.g., Acyphylla (using allozyme techniques), Arthropodium, Magnolia, and Pachycladon (using amplified fragment length polymorphism or AFLP analyses).

Current Research:

I am presently continuing research with the Araliaceae, including the phylogeny and biogeography of Brassaiopsis with Dr Jun Wen. Brassaiopsis includes approximately 25 species from Asia, distributed from the Himalayan region through China, Vietnam and Thailand into Indonesia. The genus is morphologically highly diverse with enormous variation in growth form, leaf architecture, inflorescence structure, and locular number of the ovary. This study represents the first phylogenetic investigation of the genus. Sequence data from the nuclear ribosomal ITS and 5S spacer regions are being used to test the monophyly of Brassaiopsis and to define monophyletic groups within the genus based on parsimony, maximum likelihood and Bayesian analyses. Preliminary results suggest that Brassaiopsis species are well supported as the monophyletic sister group to Trevesia, a genus from tropical and subtropical Asia. Close relationships within Brassaiopsis include: 1) B. hainla with B. glomerulata, 2) B. tripteris with B. gracilis (both of which exhibit a highly reduced inflorescence), and 3) B. ciliata with B. fatsioides and B. hispida. Palmately compound leaves were suggested to have evolved independently at least 3 times within the genus. The diversification of Brassaiopsis into different habitats and biogeographic regions in Asia is suggested to have been rapid and recent.

Other research, also in collaboration with Dr Jun Wen, includes the phylogeny of the Asian core Araliaceae clade based on Granule-Bound Starch Synthase I (GBSSI) sequence data. This represents the first study to use Granule-Bound Starch Synthase I (GBSSI) sequence data for phylogenetic analyses within the Asian core Araliaceae clade. The amplified region includes exons 10 and 11 which, together with the intervening intron, total approximately 700 bp in an aligned matrix. The level of infrageneric variation appears low relative to that among genera. Analyses based on parsimony, maximum likelihood and Bayesian methods supported several clades, including Brassaiopsis with Trevesia and Dendropanax with Merrilliodendron. The phylogenetic position of Tetrapanax has been highly controversial. The GBSSI data also suggest a highly isolated position of Tetrapanax within the Asian core Araliaceae. The GBSSI phylogeny is largely congruent with the topologies derived from nuclear ribosomal ITS and chloroplast ndhF data.

Further research planned includes a study of the genetic variation within an among populations of the 3 closely related Stilbocarpa species from the sub-antarctic islands. The objectives of this study are to 1) quantify genetic diversity and gene flow present within and among populations of Stilbocarpa, 2) assess relationships among taxa, 3) assess and discuss implications for conservation within this complex. This study will supply new insights regarding the extent of diversity within and among populations of Stilbocarpa and contribute towards a better circumscription of species.

Publications:

Mitchell, A., Edwards, R., Frampton, C. 2001. Distinguishing among Magnolia cultivars using fluorescent Amplified Fragment Length Polymorphism AFLP analysis. New Zealand Journal of Crop and Horticultural Science. 29: 77–83.

Wen, J., Plunkett, G. M., Mitchell, A., Wagstaff, S. J. 2001. A phylogenetic analysis of Araliaceae using sequences from the ITS regions of nuclear ribosomal DNA. Systematic Botany. 26: 144–167.

Mitchell, A. Wagstaff, S. J. 2000. Phylogeny and biogeography of the Chilean Pseudopanax laetevirens. New Zealand Journal of Botany. 38: 409–414.

Mitchell, A., Heenan, P. 2000. Systematic relationships of New Zealand endemic Brassicaceae inferred from rDNA sequence data. Systematic Botany. 98–105.

Mitchell, A., Hogan, K., Chapman, H. 1999. Genetic variation in Aciphylla glaucescens (Apiaceae). New Zealand Journal of Ecology. 23: 61–67.

Mitchell, A., Meurk, C., Wagstaff, S. 1999. Evolution of Stilbocarpa Gray, a megaherb from New Zealand’s sub–antarctic islands. New Zealand Journal of Botany. 37: 205–211.

Current Position:

www.chmeds.ac.nz/research/resbiomed2.htm