Working with collaborators at the Brooklyn Botanic Garden (Dr. Mark Tebbitt) and the Royal Botanic Gardens, Edinburgh (Dr. Richard Bateman and others), Dr. Susan Swensen at Ithaca College is studying the taxonomy and phylogeny of the tropical plant family Begoniaceae. With over a thousand named species published for the genus Begonia itself, the group is taxonomically complex and challenging. Horticultural interest in these tropical plants has led to large living collections at several major botanical gardens, but the classification of the numerous species has usually relied upon a restricted set of floral and vegetative features, and similarities among many of the forms are suspected to have evolved convergently or in parallel in many subgroups. Currently, about 80 sections (the rank between species and genus) are recognized in Begonia, but mostly on the basis of a few "key" characters used for herbarium identification. Dr. Swensen is emphasizing the acquisition of DNA sequence data from samples of several hundred species, from either nuclear or plastid gene regions, to be complemented by plastid or nuclear data from her collaborators for the same exemplar taxa. Undergraduate students will be active participants in all aspects of the research. Work will also start on morphological and anatomical characters, eventually for integration with the molecular database. Although recognized as a diverse component of tropical vegetation, the Begoniaceae are not well known, and the current classification provides little insight into their historical biogeography or into such interesting features of evolution as dioecy and associated pollination (separate staminate and pistillate plants within a species). The basal position of the single-species genus Hillebrandia in recent molecularly based phylogenies is particularly perplexing; this Hawaiian endemic may be a geologically recent introduction to the islands, or a more ancient relict. These and other biological questions will be answered when a framework phylogeny or family tree is established for the group, based on the new DNA sequence data and integrated with traditional morphological and chromosomal data.
