XVI International Botanical Congess
Clarkia xantiana has an evolutionarily derived selfing form of the crossing subspecies that flowers earlier, and has smaller flowers. We investigated floral development in each subspecies to establish the basis for these differences. Growth parameters were estimated by fitting growth curves to the relationship between organ size and plastochron age. All organs grow faster and most attain a smaller final size in the selfer. Final ovary size is the same in both subspecies. Principle component analysis of growth parameters results in a good separation of the subspecies. Allometric analysis of floral organs distinguishes subspecies based on a negative correlation between growth rate and final size. It has been suggested that rapid floral development and smaller size is favored due to the more arid environment in the selfers part of the species' range.