THE REPRODUCTIVE BIOLOGY OF PRIMITIVE ANGIOSPERMS

Summary Virtually all flower‐visiting insect groups had already existed at the time of early angiosperm differentiation; beetles, flies, thrips, and moths were available as potential pollinators. Unspecific interactions with these insect groups are found in the Winteraceae, archaic Magnoliidae. Winteraceae are often weedy species for which an open pollination system may be advantageous in view of the different insect faunas of newly invaded habitats. Winteraceous pollination modes and life strategies are here interpreted as close to the ancestral condition of the angiosperms. The Annonaceae provide examples of more economic and effective plant/pollinator interactions. Within this family a range exists of different adaptations for pollination by beetles. Flowers in several genera provide pollination chambers resulting from enfolding petals in which beetles stay for long periods of time. In the dark chambers the beetles are protected against environmental changes and predators. The permanently recurved microsporophylls of the flowers of the late bennettitalean genus Cycadeoidea, evolving during the early Cretaceous, may be a comparable adaptation to beetle pollination.