Diplochory and the evolution of seed dispersal.

Two-phase seed dispersal systems are simply special cases of secondary dispersal. But seed dispersal involving two distinct mechanisms of seed movement deserves special attention because two-phase dispersal can offer more benefits to plants and the most effective mechanism can shift temporally or spatially from one mode of dispersal (phase one) to another (phase two). The five two-phase seed dispersal systems are described. The adaptation of seeds, fruits and, where relevant, animals to the two phases of dispersal are discussed. The advantages and disadvantages of each phase of seed dispersal to plants are presented. The possible contribution of two-phase seed dispersal system to evolutionary change in dispersal mode is discussed.