Date of Award

Winter 12-15-2022

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Evolution, Ecology & Population Biology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type



A big question in biology is how organisms compete in an environment of competitors for scarce resources. Part of the answer lies in distinguishing friend from foe and in forging cooperative bonds in the face of cheaters. The social amoeba – bacteria system I have studied here is an excellent place to explore these tensions. The first part of my thesis research involves a review of cooperation and conflict in the social amoeba Dictyostelium discoideum and a study of the limits on obligate social cheating in this species. The second part focuses on the benefits of associating with D. discoideum for two bacterial intracellular endosymbionts, Paraburkholderia agricolaris and P. hayleyella. I also explore kin discrimination within each of these species. I found that an obligate social cheater in D. discoideum is limited by negative frequency-dependent cheating and reduced potential for dispersal. One endosymbiont that I studied, P. hayleyella, has a reduced genome and is more AT rich than non-symbiotic congeners, similar to obligate endosymbionts. I found that this endosymbiont benefits from D. discoideum in the context of interspecific resource competition while the species more similar to non-symbiont species, P. agricolaris, does not get this benefit. I found surprisingly little kin discrimination between strains of P. agricolaris and P. hayleyella.


English (en)

Chair and Committee

Joan E. Strassmann David Queller

Committee Members

Christy Edwards, Fred Inglis, Rachel Penczykowski,