Anna Lindeberg: Simplifying and Characterizing Networks via Least Common Ancestors

Abstract: Evolution shapes all life on Earth, but reconstructing evolutionary histories is complex. While biologists traditionally use tree-like structures, we now know evolution involves non-tree-like processes such as horizontal gene transfer and hybridization. Rooted phylogenetic networks capture these complex relationships better than trees, but there is no consensus on exactly which networks are most appropriate. A key biological justification for keeping a vertex in a network is that it represents a meaningful ancestor. In trees, every vertex serves this purpose: each is the least common ancestor (LCA) of some set of leaves. This seminar explores how we can apply the same principle to networks: by requiring that every vertex is an LCA of some subset of leaves, we obtain well-justified network structures.