UC San Diego

Nematodes such as Caenorhabditis elegans, C. briggsae, C. remanei, and C. nigoni are model organisms that primarily reside in rotting fruit and plant matter, feeding on the bacteria that inhabit these degrading vegetation (Frézal & Félix, 2015). When conditions are poor, worms must decide whether to go into a larval stage called dauer (Avery, 2014). Entering dauer would allow the worms to survive for months; however, the risk of dying in dauer is high and this results in a tradeoff. I created an extensive model in Python to simulate the population dynamics and decision-making strategies of worms and their responses to various environmental conditions. This model includes genes related to both dauer and travel direction decision making strategies. Experiments showed significant evolution of both genes when there is stronger selection against worms in dauer, both genes when there is higher frequency of food availability, the dauer gene only when the dauer genotype to phenotype mapping is altered, and neither gene when seasonality in terms of environmental productivity is introduced. Stronger selection against worms in dauer led them to evolve a lower likelihood of dauer and a preference for traveling away from neighbors. A higher frequency of food availability also led them to evolve a lower likelihood of dauer but a preference for traveling towards food. A higher genotype to phenotype mapping value led them to evolve a lower likelihood of dauer as well. However, there may be some underlying patterns present in many of these experiments that require further study.