Managing rare endemic plants often requires an understanding of their reproductive ecology. We investigated pollination biology, seed set, seed dispersal, and seedling recruitment of Rudbeckia auriculata (Asteraceae), a species endemic to the Southeastern United States. Based on observations of pollinator abundance and pollen load on floral visitors, the most likely pollinators are primarily native bees, particularly Andrena aliciae Robertson in medium and large populations of R. auriculata, and Halictids in small populations. Seed set varied from 0.24% to 16.9% in small populations (<40 flowering stems) and from 26.5% to 31.4% in medium (40-999 flowering stems) and large (1000 flowering stems) populations, with significantly lower seed set in the small populations. Exclusion of visitors from inflorescences showed that, like many members of the Asteraceae, R. auriculata is probably self-incompatible. Seed dispersal appears to be highly localized and dependent upon gravity. Seedling recruitment is poor, particularly when the soil is covered with litter or when the species is in competition with others.
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Vol. 71 • No. 3