Delphinium L. Subgen. Delphinium: origin and evolutionary trends

Abstract

The advanced features of Delphinium lo subgen. Delphinium(annual taxa) are compared with those of subgen. Delphinastrum (DC.) Wang and subgen. Oligophyllon Dimitrova (perennial taxa). F1ower morphology shows a functional interchange between lateral petals and upper petals. and inflorescence structure favours geitonogamy-autogamy rates. Karyotype evolution is based on a decrease in the total length of chromosomes and on an increase in the degree of asymmetry: the chromosome number remains constant (2n = 16) in the subgen. Delphinium.The dispersal efficiency of the annual species is higher than that of perennials due to seed set increase and improved floatability. both in water and in air. Other advanced adaptive features are the acquisition or new chemical weapons and the emergence of a new embryonogenic type. The ecological niches or subgen. Delphinium correspond to open and disturbed habitats in contrast to the stable and relatively closed ones or subgenera Delphinastum and Oligophyllon. A final hypothesis is made concerning the evolutionary trends observed in annuals vs. perennials in connexion with biogeographical considerations, and a final taxonomic summary is given.