Assessment of competition between the dpy-­‐5 and N2 strains of Caenorhabditis elegans

Abstract

Two strains of Caenorhabditis elegans, the N2 wild type and the dpy-­‐5 dumpy mutant, were studied to determine whether the wild type has a competitive advantage over the mutant. Three treatments were set up: a mutant control, a
wild type control, and an experimental group (mutant and wild type present at a 1:1 ratio). For each treatment, initial populations of four nematodes were plated on 100 mm Petri dishes containing Escherichia coli, and subsequently incubated at 17 °C. From the fifth to the ninth day after the initial plating, the total number of adult individuals on each treatment was recorded. This data was analyzed for significant differences in the total number of adults per original number of adults, growth rate, and the ratio of number of mutants to number of wild type. On the eighth day, the wild type control group saw a
significant increase in population, and had significantly more individuals than the mutant control group. However, on the ninth day, the mutant control group had drastically increased in population, such that there was no significant difference between the control groups; the experimental groups, however,
did not demonstrate this trend. These results were supported by the observed daily growth rates. In the experimental treatments, the ratio of wild types to mutants did not ever deviate significantly from the original 1:1 ratio. The
results do not provide any support for a competitive advantage in the wild type over the dpy-­‐5 mutant. Lack of a limiting resource, excessive biological variation, and poor representation of natural habitat are discussed as possible
issues affecting the results of this study.