|Vander Wall, Stephen - UNIV OF NEVADA, RENO|
Submitted to: Trends in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 26, 2003
Publication Date: January 1, 2004
Citation: Vander Wall, S.B., Longland, W.S. 2004. Diplochory: are two seed dispersers better than one?. Trends in Ecology and Evolution. 19(3): 155-161. Interpretive Summary: Seed dispersal refers to any active movement (via wind, water, or animals) of seeds away from the parent plant that produced the seeds. We summarized published cases where seeds are dispersed in two distinctly different steps, and we describe five examples of such two-phase dispersal or "diplochory". These examples are: (1)initial movement of seeds by wind followed by secondary movement by seed-hoarding rodents;(2) consumption of seeds within fruits by birds or mammals, followed by secondary movement by ants, which remove them from droppings of fruit-eaters; consumption of seeds by herbivorous or fruit-eating mammals, followed by secondary movement by (3) seed-hoarding rodents, which harvest them from herbivore dung, or by (4) dung beetles, which transport and bury pieces of the herbivore's dung; and (5) forcible ejection of seeds from drying pods on plants ("ballistic dispersal"), followed by secondary movement by ants. Many potential advantages of seed dispersal have been proposed. The main advantage to the first phase of diplochory is to move seeds away from parent plants, where seedlings have a better chance of surviving than they do beneath their parents. The main advantage to the second phase is to move seeds to hidden sites, where they have less chance of being discovered and eaten by other seed-eaters.
Technical Abstract: Diplochory is seed dispersal by a sequence of two or more steps or phases, each involving a different dispersal agent. Diplochory and other forms of secondary seed dispersal have emerged as important ecological processes with implications for plant fitness. Here we briefly describe five forms of diplochory and derive general characteristics of each phase of seed dispersal. The first and second phases of diplochory offer different benefits to plants. Phase one dispersal often results in escape from density-dependent seed and seedling mortality near the parent plant and may result in colonization of habitat patches far from the parent. Phase two dispersal further reduces the vulnerability of seeds to predators and often moves seeds to discrete and predictable microsites where the probability of seedling establishment is disproportionately high (i.e. directed dispersal). Diplochory appears to have evolved because combining two means of seed dispersal can increase the benefits of seed dispersal while reducing the likelihood of seed mortality.