(a) Unbounded G (b) G ′ ←G\U (c) G
of unbounded G: (a) An unbounded G. Here K = 2 corresponding to the samples numbered 1 and 2 and M = 2, for the two segments colored red and blue. The pattern of vertices and edges can be repeated along the dashed edges to give an unbounded structure. The coalescent nodes that are not t-coalescent are marked by circles: let U be the set of all such nodes. (b) G′ is obtained from G after removing the vertices in U. (c) G
is obtained by the 1-vertex compactification of G′ with the new vertex v′.