Introduction — Major trends in the study of early flower evolution

Abstract

Our knowledge of early angiosperm phylogeny and of flower evolution is rapidly expanding. New evidence comes from different directions, and it seems important to constantly synthesize new results from these fields. (1) Palaeobotany brought two major developments, first comparative structural and stratigraphie pollen studies (since Brenner 1963 and Doyle 1969), followed by the discovery of excellently preserved Cretaceous flowers (since Friis & Skarby 1981). (2) Development and biology of extant flowers and structure of modern pollen was studied in many living conservative groups during the same period. Application of the SEM for comparative floral development was especially helpful (since Endress 1972). The comparative study of pollen with combined SEM and TEM techniques provided a powerful approach to link extant and fossil material (since Walker 1976). Comparative pollination biology of primitive flowers in relation to floral structure brought another new dimension (since Gottsberger 1974). (3) The application of cladistic techniques facilitated the rigorous discussion on the origin of the angiosperms from other seed plants and on early angiosperm diversification (since Crane 1985, Doyle & Donoghue 1986). (4) More recently comparative molecular studies with DNA and RNA became possible due to new techniques, applied for macro-systematics of angiosperms (since Jansen & Palmer 1987).