Integrated Studies of Floral Development, Traditional and Molecular Systematics, and Floristics in the Violet Family (Violaceae)

Ohio University, Athens OH

Investigators

Abstract

0211054 Ballard and Tucker Generic distinctions and major subdivisions within many angiosperm families commonly hinge on characteristics of floral symmetry or architecture, and morphology of the reproductive structures themselves. This is true in the violet family (Violaceae), a moderate-sized family of angiosperms with a broad range of growth forms from large tropical forest canopy trees to fingernail-sized Andean puna rosettes. Predominately insect-pollinated, the family nevertheless boasts a wide range of floral and fruit morphologies on par with that in whole orders of other angiosperms. An apparently simple trend from actinomorphy to extreme zygomorphy, coupled with increasing elaboration of staminal nectaries in floral spurs, has figured heavily in generic concepts as well as in assignments to tribes and subtribes. Recent studies of generic relationships based on sequences of the trnL-F and rbcL chloroplast regions, however, reject the simplistic trend in floral symmetry and nectary development, as well as the current traditional classification based on this trend, revealing instead several independent origins of bilaterally symmetrical floral types with spurs from different radially symmetrical spurless lineages. Furthermore, pantropical Hybanthus, the third largest genus in the family, splinters into 7 separate groups distributed across the family, suggesting that its distinctive "landing platform" flower is a recurrent evolutionary syndrome. The second largest pantropical genus, Rinorea, is also substantially heterogeneous and non-monophyletic. The proposed research program will integrate comprehensive floral developmental investigations to clarify floral evolution; systematic studies of macro- and micromorphological characters, chromosome numbers, xylem anatomy and pollen morphology to reevaluate circumscriptions and distinctions of genera and diagnosable segregates; and inferences of generic relationships from chloroplast trnL-F spacer and rbcL gene regions to provide a robust molecular phylogenetic foundation on which to test relationships and develop a predictive classification. Complete generic circumscriptions using the new and pre-existing traits, and a new intrafamilial classification, will then be developed using examinations of key herbarium collections at the Missouri Botanical Garden in St. Louis, Missouri; Royal Botanic Garden at Kew, England; and the National Museum of Natural History in Paris, France. Field work in Latin America by the investigator and his students and herbarium and laboratory training for graduate students add to the broader impacts of the work, as does collaboration with a leading plant morphologist, Dr. Shirley Tucker at UC-Santa Barbara.