Dispersal of Small Seeds by Big Herbivores: Foliage is the Fruit

Abstract

Many species of herbs (including grasses) have some of their seeds dispersed by the large grazing mammals that consume the seeds along with foliage. This is an interaction that has probably been occurring for many millions of years. It should result in a very effective kind of seed dispersal to sites newly open for colonization in a wide variety of habitat types. It should select not only for seeds with the traits that enhance survival percentage or amount during the trip though the animal (small size, large numbers, resistant seed coats), but for edibility of the plant's vegetation either at the time of ripening of seeds or throughout the vegetative life of the plant. Such a view of the vegetative structure of a herb as the functional fruit ("bait" for the dispersal agent) confounds attempts at understanding leaf defensive chemistry and seed coat traits solely in the context of fitness-depressing herbivory or seed dormancy.