Many plant populations fluctuate between years of high and low
seed production. These fluctuations, often called mast-seeding,
have typically been attributed to fluctuations in resource
availability. Recent theoretical models show that mast-seeding
could also be due to the dynamics of resource allocation within
individuals, synchronized among individuals by pollen limitation
in low flowering years. This "pollen coupling" mechanism appears
to explain synchronous, alternate-year flowering in a perennial
wildflower, Astragalus scaphoides. Our past research shows that
plants are more pollen limited in low-flowering years, and that
pollen coupling models fit to data for this species predict
alternate-year flowering in the absence of environmental
forcing. Here, we present tests of two additional components of
pollen coupling. First, we directly tested whether preventing
fruit set caused plants to flower in successive years. Removing
flowers in 2005, a high flowering year, caused these plants to
flower again in 200