XVI International Botanical Congess

Most studies of rarity have been conducted from ecological and population genetic frameworks. While evolutionary history is believed to be important in explaining rarity, studies using phylogeny have been almost entirely lacking. Work presented here is based upon results of a morphological cladistic study of 47 species, many of which are rare. Biogeographic data for each species, based upon published distribution dot maps, were plotted on grids at six spatial scales (10km - 320km) using ArcView GIS. Range sizes and geometries where characterized using minimum cell occupancy counts. Analyses addressed the question: Do rare species cluster phylogenetically? The result of a Mantel Test (p=0.13) does not significantly support an affirmative answer. Other results indicate that most of the rarest species are recently derived. Results, however, depend on spatial scale.