Date Thesis Awarded
Bachelors of Science (BS)
The relationship between scatter-hoarders and trees varies on a continuum from mutualism to antagonism and can change across time, location, and among species. We examined five tree species across five sites to quantify this variability: red oak (Quercus rubra), white oak, (Quercus alba), American chestnut (Castanea dentata), Chinese chestnut (Castanea mollissima), and a hybrid American/Chinese chestnut. In the fall of 2012, 2013, and 2015, we set up field sites across the east coast, including in Virginia, Pennsylvania, Indiana, Massachusetts, and Maine. We tested the potential for mutualism between scatter-hoarders and trees by using a simple model proposed in the literature that compares rates of seedling emergence with and without scatter-hoarders. The model uses the ratio of seed emergence from the surface divided by seed emergence from a cache (Es/Ec) as one variable to place seeds on a continuum from mutualism to antagonism. We predicted across different study sites and found that that red oak seeds will have a more mutualistic relationship with scatter-hoarders because of their long dormancy period before germination, white oak seeds will have an antagonistic relationship because they germinate readily, and chestnuts will fall in between. We hypothesized that abiotic conditions surrounding the seed would have a stronger influence on the Es/Ec ratio than the provenance of the seed would. We found that different seed provenances caused variation in the Es/Ec ratio, but abiotic conditions described more of the variation in the continuum from mutualism to antagonism. We also quantified the effect of temperature at our different study sites to measure the correlation between temperature and emergence. We found that temperature did not predict the high degree of variation in the effect of abiotic conditions on the degree of mutualism.
Sawaya, Gina M., "Quantifying Variation in the Seed Scatter-hoarder Relationship" (2016). Undergraduate Honors Theses. Paper 1000.