Traditionally, genetic history of species has been modeled using phylogenetic trees. Recently, scientists have begun using phyolgenetic networks to model more complex occurrences, such as hybridization, which cannot be displayed by trees. Phylogenetic networks are represented by network graphs which are trivalent, directed graphs without directed circuits. In this paper we discuss the mathematics of network graphs. Given an unoriented trivalent graph, we determine a necessary and sufficient condition for orienting the graph as a network graph.

Author Bio

I am a senior at Lexington High School in Massachusetts and I plan on majoring in math or computer science in college. I presented this project at the Massachusetts State Science and Engineering Fair in 2007.