Ecological Dispersal Classes, Established on the Basis of the Dispersing Agents

Abstract

The sequence in which the various classes in dispersal ecology are to be presented seems at first irrelevant, as each agent, in principle, has the same rights. The question arises, however, whether historically the different agents could and did exert their rights equally well. The sequence used in most handbooks, although neither logical nor historically correct, has found wide acceptance, so that I have to justify my own deviating order; the more so, as our chapter on evolution will prove the existence of a certain line of development which does not start with the anemochory or autochory often assumed to be basic. In Pteridosperms and Gymnosperms we shall find reasons to consider dispersal of seeds by animals to be dominant. The wind dispersal of some Pinus seeds is derived from the animal dispersal in large-seeded species. The concept of anemochory as basic goes back to Sernander (1927), who was probably misled by the prejudice of his time as well as by the special situation prevailing in Europe. Thus he was influenced by: 1. the one-sidedness of European Gymnosperms, as anemochores; 2. the neglect of Ranales as primitive; 3. a false analogy between seeds and wind-dispersed spores; 4. the false concept of basic wind pollination in Amentiferae and of the primitivity of this group; 5. the concept that small seeds are basic.