PARENT SESSION
Poster Session # 16: Invasive Species.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Invasion of Chinese Tallow (Sapium sebiferum): Dispersal and recruitment limitation in multiple habitats.
Samuels, Ivan*,1, 1 University of Florida, Gainesville, Florida, USA
ABSTRACT- Studies of exotic plant invasions have often focused on spread and impact of these species, as well as the processes that facilitate invasion. However, little attempt has been made to understand why particularly invasive plants do not establish in potentially suitable habitats where dispersal of their seeds may be high. I compared both dispersal and post-dispersal processes of Sapium sebiferum (Chinese Tallow) in four habitats, two wet prairie habitats where the plant is currently invading, and two adjacent forest habitats where it is absent, but where it occurs elsewhere in its non-native range. I observed foraging birds to quantify the number of seeds removed and post-foraging movements, and used point counts to estimate the density of seed dispersing bird species in the non-invaded habitats. In addition, I experimentally placed seeds in each of the four habitats to compare seed predation, germination, and seedling survivorship rates. Of 30 species of birds that visited trees, 53% ingested seeds and 20% carried seeds away from parent trees. After foraging, these species frequently moved into forest habitats, where they were commonly detected on point counts. Thus, dispersal limitation is unlikely to explain the absence of S. sebiferum in the two forest habitats. Differences in seed predation are likewise unable to explain recruitment limitation in forest sites, as it was significantly lower than in wet prairie. On-going germination tests and monitoring of seedlings will identify the stage/s that act as a barrier to establishment in forest habitats, and the relative importance of these stages on the overall probability of recruitment.
Key words: invasion, Sapium sebiferum, dispersal, recruitment