Portland State University. Department of Biology
Date of Award
Master of Science (M.S.) in Biology
1 online resource (viii, 51 pages)
Seed dispersal is a crucial ecological and evolutionary process that allows plants to colonize sites and expand their ranges, while also reducing inbreeding depression and facilitating the spread of adaptive genetic variation. However, our fundamental understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. In recent years, genetic marker methods have furthered our understanding of colonization and range expansion due to seed dispersal. Most investigations focus on regional scales of dispersal, due to low levels of variation in the chloroplast genome (cpDNA), which can serve as an indirect measure of seed dispersal. Here, I employ a whole-genome assay of cpDNA variation in Plagiobothrys nothofulvus to resolve variation due to patterns of seed dispersal within a 400x400 meter section of the Whetstone Savanna Preserve in Central Point, OR, USA. Whetstone is characterized by a mosaic of habitat types, including vernal pools, hummocks of dry prairie, and large Ceanothus cuneatus bushes, as well as a network of vole runways. Plagiobothrys nothofulvus grows in dense patches on hummocks within this prairie.
I found evidence of limited seed dispersal in P. nothofulvus, indicated by strong genetic structure over distances of less than 100 meters. There was little evidence that geographic distance predicts genetic distance; environmental features have a stronger influence on dispersal. Habitat preference was the strongest predictor of genetic variation in P. nothofulvus, indicating that it may be a habitat specialist in this prairie. Flower density also accounted for a significant portion of dispersal, which may be a consequence of the annual life history of P. nothofulvus resulting in seasonal turnover and lack of competition with adult plants. Least-cost-path analysis indicated that seeds are secondarily dispersed by small mammals along vole runways. Overall, I found significant evidence that landscape features influence dispersal, even at a very fine spatial scale.
Grasty, Monica R., "Let the Seeds Fall Where They May: Investigating the Effect of Landscape Features on Fine-Scale Seed Dispersal" (2017). Dissertations and Theses. Paper 4001.
Appendix A: Genetic distance
Copy of AppendixB_GeographicDistance.xlsx (14 kB)
Appendix B: Geographic distance
Copy of AppendixC_HabitatResistance.xlsx (13 kB)
Appendix C: Habitat resistance
Copy of AppendixD_RunwayResistance.xlsx (14 kB)
Appendix D: Runway resistance
Copy of AppendixE_DensityResistance.xlsx (14 kB)
Appendix E: Density resistance
Copy of AppendixF_Habitat_Density.xlsx (13 kB)
Appendix F: Habitat density
Copy of AppendixG_Habitat_Runways.xlsx (13 kB)
Appendix G: Habitat runways
Copy of AppendixH_Runways_Density.xlsx (14 kB)
Appendix H: Runways density
Copy of AppendixI_LCP_VoleRunways.xlsx (12 kB)