PARENT SESSION
Poster Session #32: Plant-Animal Interactions I.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Seed dispersal, seed predation, and the distribution of plants in early-successional habitats.

Orrock, John^*,1, Levey, Douglas², Danielson, Brent¹, Brinkerhoff, Robert³, ¹ Ecology and Evolutionary Biology Interdepartmental Program, Ames, IA² Department of Zoology, Gainesville, FL³ Department of Zoology, Raleigh, NC

ABSTRACT- Plants may be absent from suitable habitats if seeds fail to colonize suitable habitats (dispersal limitation), find suitable sites for germination and growth (microsite limitation), or survive biotic interactions (e.g. competition or predation). Using three data sets, we determined the importance of seed dispersal and seed predation in affecting the distribution of Pokeweed, Phytolacca americana. We evaluated the importance of dispersal limitation by adding approximately 10,000 seeds to 8 of 40 recent clearcuts in November 1999 and March 2000. The role of seed predation was examined in the same 40 clearcuts using experimental exclosures from June 2000 - July 2001. Complementary data describing the abundance of small mammals from May-August 2000 were also collected. In October 2000, we surveyed Phytolacca in all plots. The number of Phytolacca plants did not differ due to seed addition. Rather, fewer Phytolacca plants were found in patches where rodents removed more seeds from experimental exclosures. Moreover, the number of oldfield mice, Peromyscus polionotus, was a significant predictor of the number of Phytolacca plants in a patch. These data suggest that Phytolacca was not limited by seed dispersal. Rather, the distribution of Phytolacca may be limited by rodent seed predation.

KEY WORDS: Seed predation, Seed limitation, Rodent, Plant distribution