Three-Taxon Tree

THREE-TAXON TREE. Pinus pinea, Italian stone pine.
Median of Page Mill Road south of Foothill Expressway, looking west.

The simplest nontrivial rooted phylogenetic tree has three taxa: A, B, and C. Three topological relationships are possible: A and B can be the two most closely related groups, A and C can be the most closely related, or B and C can be the most closely related.

Photo: Noah Rosenberg, October 2, 2016