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PAINTING: All plants with seeds were airbrushed with fluorescent paint. Liatris squarrulosa was airbrushed green; the remaining species were airbrushed orange. Seeds of L. squarrulosa and C. bellidifolius are difficult to distinguish by sight, which is why different colors were used. Seeds of other species are easily morphologically distinguished. Up to 10 flower heads (L. squarrulosa and C. bellidifolius) and up to 5 grass stalks (S. secundum, A. villosa, A. beyrichiana) were airbrushed. Cardboard shields were used to avoid paint splatter. After painting, dispersal heights were measured with a tape measure. For L. squarrulosa and C. bellidifolius, the height of the center of each head was measured. For the grasses, the height of the highest seed on each stalk was measured. The stalks were measured as they stood on their own (leaning or bowed stalks were not straightened or adjusted for measurements).

SEED SEARCHING: After dark, the ground was systematically searched with UV-flashlights up to 5 meters around each sprayed plant. A pin flag was placed by every seed that was found. When there was a clump of seeds (often S. secundum awns would twist together or L. squarrulosa/C. bellidifolius flower heads would disperse as a unit) a note was made on the pin flag and recorded when the flags were removed from the plots. These seeds that were in clumps were split up and listed at the same distance in the data and a note was made in the notes field. The seed searching took place in two rounds. In the first round, transects I and IV were searched in all experimental blocks. In the second round, transects II and III were searched for seeds. The one exception is 52 because it was the first block visited; Patch 52E was all searched in round 1, Patch 52A transects IV and III were searched in round 1 and Patch 52A transects I and II were searched in round 2.

DATA COLLECTION: We pulled out the pin flags and recorded data on the general direction and distance from the plant. We used a device constructed of cardboard with 8 pin flag spokes spreading off at 45-degree angles. Each pie-wedge section was labeled with a number based on the direction of the patch’s corner.

To collect the data, we centered the spokes over the middle of the reproductive plant, and marked the appropriate sections around the plant. We held a tape measure at the plant’s center and recoded which 45-degree section each seed fell within and the distance from the plant’s center point. On the first day of data collection, we were taking the measurements to the nearest millimeter; however, we decided that measurements rounded to the nearest centimeter were at a more appropriate scale based on the size of the seeds and the accuracy with which we placed the pin flags during the night searches and subsequently all measurements were made to the nearest centimeter. Any seeds encountered beyond the 5m search radius were later dropped from the data, so we could keep the effort for the search at the same level.