Research Interests

My research in evolution has included studying an advantage to sociality in the slime mold Dictyostelium discoideum. When starving, the normally solitary amoebae of D. discoideum aggregate to form a differentiated multicellular organism called a slug.  In its natural soil habitat, the slug migrates to the soil surface by moving away from ammonia and towards light.  The slug will then form a fruiting body, where twenty percent of the cells form a dead stalk that holds aloft a ball of the remaining cells, known as a sorus. Fruiting body formation has long been thought to aid in the long distance dispersal of cells by passing invertebrates or water.  By time lapse photographing slugs crossing a strip of their bacterial prey, I showed an additional advantage to slime mold sociality in the form of local dispersal. The cells in a slug are covered by an extracellular matrix of cellulose and protein that is left behind as a collapsed tube, or slime trail, as the slug migrates. Initially, the slug appears to have no reaction to the bacteria, and migrates over the strip without consuming it. However, the slime trail it leaves contains some cells that I showed are able to eat bacteria, reproduce, and continue their life cycle.  In this way, as the slug migrates, the trail with cells it leaves behind can consume local food sources the slug encounters, but cannot utilize itself.

Recently, the complete Dictyostelium discoideum genome has been sequenced, which makes D. discoideum an exciting research subject in the field of social evolution.  Unlike other model organisms for social behavior, we have the ability to examine the genetic mechanisms underlying sociality in D. discoideum.  To examine cooperation in D. discoideum, I will perform mixing experiments between a genetically distinct clone and the same clone with a single gene knocked out, called a mutant. By fluorescently labeling one of the clones and performing 50:50 mix experiments with the other clone I will be able to look for cheating.  Cheating occurs when one clone is able to get a disproportionate number of their cells into the sori, giving that clone a greater chance to reproduce compared to the other clone which contributed more of its cells to the dead stalk.  Because there is only a difference of one gene between these clones, we know that this gene is affecting cooperation.  These studies will aid in understanding the mechanisms behind cooperation and conflict suppression in D. discoideum.