Advisor

Mitch Cruzan

Date of Award

5-19-2017

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Biology

Department

Biology

Physical Description

1 online resource (viii, 51 pages)

DOI

10.15760/etd.5885

Abstract

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.

Description

Note: Appendices A-H are included below as supplemental files.

Persistent Identifier

http://archives.pdx.edu/ds/psu/22707

Copy of AppendixA_GeneticDistance.xlsx (11 kB)
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)

Available for download on Friday, November 30, 2018

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