Abstract
Post-dispersal predation on seeds of the semi-desert herbaceous perennial Cryptantha flava A. Nels. (Boraginaceae) was examined as a function of both seed density and microhabitat, under a shrub or in the open. The dispersal unit of this species consists of a deciduous calyx which usually encloses a single persistent nutlet (seed) and three aborted ovules. About 15% of the dispersal units contain two seeds. Density was altered by scattering a constant number of dispersal units over areas of different sizes as they would be following natural dispersal by wind. More seeds were removed from high density than low density plots, but there was no difference between microhabitats and no microhabitat X density interaction. The remains of opened calyces suggested that rodents were primarily responsible for the seed removal. In a separate experiment, predators did not discriminate between oneand two-seeded dispersal units, but they only removed one seed from about 4% of the two-seeded dispersal units that they opened. Thus seed predators may be an important selective force maintaining adaptations for wind dispersal but probably have little effect on the number of seeds that mature per dispersal unit.
Published Version
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