Research Interests

The evolution of life has resulted in the cooperative aggregation of cohesive units that prosper together. These units may be the same, as with the evolution of multicellularity, or they may be different, as with the evolution of the eukaryote cell. For such cooperation to evolve, conflicts at lower levels must be controlled.  We study the evolution of cooperation and the control of conflict in a microbial eukaryote, the social amoeba Dictyostelium discoideum. It is uniquely suitable for this work because transitions that are fixed in most organisms are still flexible. This amoeba preys on bacteria but, when starved, aggregates into a multicellular body that moves towards light, and then differentiates into 20% dead stalk cells that support 80% living spore cells.  When the multicellular stage is chimeric, the opportunity for one clone to cheat the other arises. We identify genes involved in this process, look at their rates of evolution using 20 resequenced clones and a handful of sequenced closely related species. We use experimental evolution to look at the robustness of the social process and the importance of high genetic relatedness within fruiting bodies in maintaining the altruistic caste. We explore kin recognition and its genetic basis. We study the evolution of development by constructing pseudo-organisms with artificial life cycles where we manipulate things like single-cell bottlenecks. We have found that some clones carry bacteria with them in a farming and defensive mutualism, and use this to experimentally study mutualism.  In sum, our group studies what’s crucial to organismality.

Figure Caption: The social stage of Dictyostelium discoideum is triggered by starvation. Then some cells die to form a stalk, while others form spores on top. We starved cells for four hours and them mixed them 1:1 with unstarved cells to see if the first to signal, the starved cells, became altruists by joining the stalk, or if they selfishly became spores. We found the latter to be the case, which raises the question of why late joiners evolve to join likely cheaters (Kuzdzal-Fick et al. 2010).

Selected Publications

Kuzdzal-Fick, J. J., Strassmann, J. E., & Queller, D. C. 2011. High relatedness is necessary and sufficient to maintain multicellularity in Dictyostelium. Science 334: 1548-1550. DOI: 10.1126/science.1213272.

Douglas, T. E., Kronforst, M. R., Queller, D. C., and Strassmann, J. E. 2011. Genetic diversity in the social amoeba Dictyostelium discoideum: Population differentiation and cryptic species, Molecular Phylogenetics and Evolution 60:455-462.

Strassmann, J. E. & Queller, D. C. 2011. Evolution of cooperation and control of cheating in a social microbe. Proc. Natl. Acad. Sci. USA 108:10855-10862.

Strassmann, J. E., Gilbert, O. M., & Queller, D. C. 2011. Kin discrimination and cooperation in microbes. Annual Review of Microbiology 65:349-367.

Strassmann, J. E., Page, Jr., R. E., Robinson, G. E., Seeley, T. D. 2011 Kin selection and eusociality. Nature, 471, E5-E6 doi:10.1038/nature09833

Richard Sucgang, Alan Kuo, Xiangjun Tian, … Joan E Strassmann, David C Queller, Adam Kuspa, Igor V Grigoriev, 2011 Comparative genomics of the social amoebae Dictyostelium discoideum and  Dictyostelium purpureum Genome Biology 2011, 12:R20

Brock, D. A., Douglas, T. E.,Queller, D. C., Strassmann, J. E. 2011. Primitive agriculture in a social amoeba. Nature 469:393-396.

Kuzdzal-Fick, J. J., Queller, D. C., Strassmann, J.E. 2010 An invitation to die: initiators of sociality in a social amoeba become selfish spores. Biology Letters doi: 10.1098/rsbl.2010.025.

Strassmann, J. E. and Queller, D. C. 2010. The social organism: congresses, parties, committees. Evolution 64:605-616

Santorelli, L. A., Thompson, C. R. L., Villegas, E., Svetz, J., Dinh, C. Parikh, A., Sucgang, R., Kuspa, A., Strassmann, J. E., Queller, D. C., Shaulsky, G. 2008. Facultative cheater mutants reveal the genetic complexity of cooperation in social amoebae. Nature 451:1107-1110.