Broman KW, Kim S, Sen Ś, Ané C, Payseur BA (2012) Mapping quantitative trait loci onto a phylogenetic tree. Genetics 192:267-279 PubMed pdf (1.9M) source on github

Broman et al. (2012) Fig 2

Figure 2. — A phylogenetic tree with six taxa (A) and three possible choices of five crosses among the six taxa, with nodes denoting taxa and edges denoting crosses (B–D).