The phenology of sexual reproduction inGinkgo biloba: Ecological and evolutionary implications

This study examines how the latitude of cultivation ofGinkgo biloba affects the timing of all phases of its sexual reproductive cycle, from pollination through germination. Seeds produced by trees growing in warm-temperate climates germinate earlier in the year than seeds produced in cold-temperate climates, and they have a longer period of time available for seedling establishment. The embryos ofG. biloba seeds possess a temperature-dependent developmental-delay mechanism that allows seeds to survive winter by preventing premature germination in the fall. This and other cold-climate adaptations appear to have evolved within the genusGinkgo during the early Cretaceous, when the Northern Hemisphere was undergoing dramatic cooling after a long period of stable, warm conditions.Ginkgo biloba seeds possess an odoriferous sarcotesta that attracts mammalian scavengers in Asia-most notably members of the Carnivora—presumably by mimicking the smell of carrion. Seeds cleaned of their sarcotesta germinated faster and at higher percentages than those with their sarcotesta intact, suggesting that animal dispersal plays an important role in promoting seedling establishment. During the Cretaceous, potential dispersal agents included mammals, birds, and carnivorous dinosaurs.