First Advisor

Mitchell Cruzan

Date of Award


Document Type


Degree Name

Bachelor of Science (B.S.) in Biology and University Honors






Seeds -- Dispersal, Plant morphology, Climatic changes, Seeds -- Variation, Phenotypic plasticity




Biodiversity is important for ecosystem health and sustainability, especially in the current, rapidly changing climate. Understanding the underlying causes behind morphological variation will allow for more accurate predictions about how a population will respond to climate change, and potentially yield better natural resource management strategies. Achyrachaena mollis is an annual, self-fertilizing, range-limited, endemic species found in Northern California and Southern Oregon. This species depends primarily on wind seed dispersal for gene flow, making it a good study species in seed dispersal experiments. Additionally, A. mollis is more readily influenced by changes in its environment than a perennial due to its annual nature. In this study, I analyzed morphological variation among eleven populations of A. mollis seeds against variation in both chloroplast DNA (cpDNA) haplotypes and environmental factors. Morphological seed traits varied significantly between populations (P < 0.01, N = 1,181), providing material for selection and evolution. Morphological variation was found to correlate with cpDNA variation (P < 0.10). This indicates that morphological diversity is likely the product of long-term cycles of mutation and evolution. Additionally, morphological variation correlated with soil-clay content (P < 0.05), likely due to availability of water and nutrients.


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Plant Biology Commons