In addition to great diversity in floral structure and modes of pollination, extant angiosperms also exhibit astonishing variety in fruit and seed morphology. This variety reflects a great range of different modes of dispersal as well as other aspects of dispersal biology. Dispersal and establishment is a key phase in the plant life cycle. Dispersal allows new populations to be established and new habitats to be colonised. It therefore has an important influence on the structure of plant populations. The evolution of angiosperm dispersal modes may have had important consequences for large-scale patterns of angiosperm evolution.
As with pollination, dispersal in angiosperms and other seed plants may be abiotic or may involve interactions with animals. However, in contrast to pollination, where pollen is carried from flower to flower, in dispersal the destination for the propagule is generally much less tightly constrained (Wheelwright and Orians, 1982). The potential reward for the disperser is also available only at the outset, rather than also on completion. The evolutionary dynamic is therefore different. As a result, co-evolution between plants and their dispersers may be much less specific than is often the case for pollination (Wheelwright and Orians, 1982). Co-evolution is more likely to be ‘loose’ rather than ‘tight’ (Herrera, 1985; Fleming, 1991).