Master of Science (M.Sc.)
Virginia Institute of Marine Science
Seed dispersal and seed predation are two important processes in the early life history of plants. The interaction between these two processes influences the population recruitment from a parent plant. These mechanisms have been studied extensively in terrestrial plants and have resulted in various models to describe plant recruitment (e.g. Janzen-Connell, Hubbell, McCanny). However, seed dispersal and predation may also influence the population recruitment of marine angiosperms, such as Zostera marina (eelgrass). The objectives of this study were to determine: 1.) the patterns of seed dispersal as a function of distance from the seed source, 2.) the predation pressure on seeds within and outside the parent bed, 3.) the distribution of seedlings as a function of distance from the parent bed, and to test if this distribution corresponds to the seed dispersal and predation pressure, and 4.) how the observed patterns compare with simulated seedling establishment using a model developed by Nathan and Casagrandi (2004).
Seed densities were highest within, and adjacent to, vegetated areas. However, some seeds were found up to 320m from the closest seed source. Seed predation was random throughout the study area; there was no significant difference in predation pressure between vegetated and unvegetated areas. Seedling densities in the spring of 2014 were highly correlated with seed densities found in the previous year, which also suggests that seed predation has a limited impact on population recruitment. The high reproductive output of Z. marina as well as the random distribution of seed predators in both vegetated and unvegetated areas may explain how many seeds are able to escape predation.
These results are consistent with the invariant survival model, first described by McCanny, which states that seed predation has no spatial trend. Therefore, a majority of the dispersed seeds remain close to the parent bed, while a small portion of seeds disperse farther from the source. This is the first study of marine angiosperms to address seedling recruitment as a function of dispersal and predation from a parent source and has important implications in recovery and restoration of these systems following disturbances.
© The Author
Manley, Stephen R., "The Roles of Dispersal and Predation in Determining the Seedling Recruitment Patterns of a Zostera marina System" (2014). Dissertations, Theses, and Masters Projects. Paper 1539617948.