PARENT SESSION
Contributed Oral Session 36: Late Breaking and Newsworthy Research: Distribution; Disturbance
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal
Role of community context in a seed dispersal mutualism.
Yang, Suann*,1, Yang, Sylvia2, Pascual, Francis1, Bishop, John4, 1 Washington State University, Pullman, Washington, United States2 Harvard University, Cambridge, Massachusetts, United States4
ABSTRACT- A major challenge in the study of seed dispersal is connecting plant distribution and the process of dispersal. Examining variation in seed dispersal across a geographic mosaic may provide a way to bridge this gap. Specifically, the location of an individual can affect its seed dispersal because of differences in community composition that vary with geography. To understand these spatial effects, we studied Vaccinium membranaceum in two community types (primary and secondary succession) at Mount St. Helens. We examined the variation between species interactions with V. membranaceum that influence fruiting display, and then interpreted these results with respect to the effect of variation in fruiting display on frugivore foraging activity. We found significant differences between primary and secondary successional sites in fruit crop size due to variation in pollination (F1,16=4.19, p=0.057), fungal infection of fruits (F1,32=19.39, p<0.0001), and pre-dispersal seed predation (F1,34=4.95, p=0.033). An approximately 50-fold reduction in crop size was found in primary compared to secondary succession, which has fitness implications for plants located in primary successional sites. In previous work, we have found that fruit crop size has a significant effect on removal rate by frugivores. Plants with lowered fruit crop sizes have lower rates of removal by frugivores; thus, plants in primary succession may have lower visitation and fruit removal compared to their conspecifics in secondary succession. We conclude that a new population in primary succession will experience limited population growth, or growth dependent upon migration of individuals from secondary successional sites. Significant asymmetrical gene flow from secondary succession may interfere with the ability of this new population to adapt to its novel environment. This study shows that geographic variation in community composition can play a large role in determining the outcome of dispersal, with consequences for population dynamics.
Key words: geographic mosaic, seed dispersal, Mount St. Helens, colonization