In particular, I am fascinated by the diversity and biology of the orchid family (Orchidaceae). In collaboration with an international team of scientists, I have published a cladistic analysis of rbcL nucleotide sequence data from taxa representing nearly all tribes of Orchidaceae. This study resulted in hypotheses of phylogenetic relationships that divide the orchids into five monophyletic clades that essentially correspond to currently recognized subfamilies. At the same time, the results challenge some traditional aspects of orchid classification as well. In addition, I have been sequencing the 18S nuclear ribosomal gene for each orchid subfamily. The results of this ongoing study appear to be congruent with the rbcL results. Each of these projects and others will contribute greatly to our understanding of this most diverse family of flowering plants. More work needs to be done, and I am part of a small group of orchidologists who are collaborating in this area of study.
My most current research is concerned with increasing our knowledge of a poorly studied group of orchids that includes Vanilla and allied genera. The results from examination of plastid and nuclear DNA sequences along with seed morphology and leaf architecture seems to indicate that the vanilloid orchids form a distinct clade that would best be classified as a subfamily (Vanilloideae) and that they are the sister-group to all orchids with a single, fertile anther. This is a fascinating group of relict species that is undoubtedly pivotal in our understanding of orchid evolution but is under severe threat of extinction because of habit destruction.
Other taxa of special interest to me include the monocot genus Smilax. Although part of a relatively small family, it is of some economic value as the source of sarsaparilla flavoring, and certainly demands greater systematic attention because of its unusual display of reticulate leaf venation. There are no contemporary taxonomic treatments of the family and no attempts have been made to assay the anatomical variability or phylogenetic relationships among the species.
The monocot genus Petrosavia (Petrosaviaceae) is also of interest because of its achlorophyllous and greatly reduced habit. Individual plants are leafless, and the flowers consist of little more than six tepals, three free carpels, and six stamens. This considerable reduction in morphology has been cause for debate over the proper classification of the family. During a collecting trip to Borneo, I was fortunate to find flowering specimens of the rare genus. Although the plants are not photosynthetic, I found them to contain an intact copy of the plastid gene rbcL. Results of molecular analyses indicate that Petrosavia is closely related to Dioscoreaceae near the base of the monocot tree. This result has never been suggested and requires confirmation from anatomical research which is being done in collaboration with Paula Rudall at Kew.
In addition to a strong interest in monocotyledons, I am also involved in systematic studies centered on taxa from dicot families including Dioncophyllaceae, Ancistrocladaceae, Sarraceniaceae, Cunoniaceae and a large, multi-gene, molecular analysis of Malpighiaceae in collaboration with Bill Anderson and Mark Chase.
Finally, I have a strong interest in educating young biologists and the public about the joy of plant research and importance of conserving our rich botanical resources. I pose to them and to you the question first asked by Henry David Thoreau beside Walden Pond, "Shall I not have intelligence with the earth? Am I not partly leaves and vegetable mould myself?"