Suzanne Seager - Variants of competition graphs

The food web of an ecosystem is the directed graph in which the arcs indicate which species prey on which other species. The competition graph of a food web is obtained by putting an edge between two species if and only if they have a common prey. Competition graphs arose in biology, but many graph theorists have worked on the problems such as characterizing which graphs can theoretically occur as competition graphs. Others have introduced variants involving common predators as well as common prey. We will look at these variants, and some of the characterization results that can be obtained for them.