PARENT SESSION
Oral Session #31: Plant Reproductive Ecology, Pollination, and Dispersal. Presiding: J. Karron.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Hall of Ideas L&M.
Relationships among reproductive output, dispersal, and seedling establishment in experimental populations of wild sunflowers.
Moody-Weis, Jennifer1, Alexander, Helen1, Mott, Danielle 1, Pilson, Diana2, Snow, Allison3, 1 2 3
ABSTRACT- It is often hypothesized by plant population biologists that populations with higher seed production will have a greater probability of a) persistence through time and b) dispersal of seeds further from the parent site. We tested these hypotheses with the wild sunflower, Helianthus annuus. In 2000, two replicate sets of experimental plots were established, one in northeastern Kansas and one in central Nebraska. Each plot consisted of 48 populations (2 x 2 m) made up of either 16 or 21 individual plants. Number of heads produced per plot was counted through-out the flowering season. Seed dispersal was measured at the Kansas site using seed traps placed at four locations relative to each population (in the center, at the edge, and 60 cm and 3.2 m from the edge). Flower-head production was greater at the Kansas site. There was also considerable variation in total head production per plot among populations (KS range:54-207; NE range 15 to 175). The number of seeds per trap was greatest in the center of the population (mean = 12.8) and decreased with increasing distance from the population (means: edge = 5.7, 60 cm = 1.8, 3.2 m =.37). There was no correlation found between head production per plot and the number of seeds caught in any of the traps. Subsequent observations will determine the degree to which seedling and adult plant numbers and locations in 2001 are related to reproductive output on 2000.
KEY WORDS: Helianthus annuus, seed dispersal, reproductive output, seedling recruitment