Seed production in a prairie legume (Astragalus canadensis L.) : Interactions between pollination, predispersal seed predation, and plant density.

The effects of pollination, predispersal seed predation, and plant density upon seed production of Astragalus canadensis L. in a tall-grass prairie were studied by experimental manipulation of plant density. Seed production was greater at high than low plant densities; this was inferred to result from differences in pollination success. Predispersal seed predation was lower at high than low plant densities. The relative seed production of different densities of A. canadensis was predicted based upon pollination success and the host detection ability of the predator. Increased seed production and modification of the environment by high densities of A. canadensis appears to maintain a clumped distribution of this species, while also producing new clumps at a low rate.