After studying this chapter, the student should understand the following concepts:

✓ Phylogeny as classification

✓ Evolutionary rates

✓ Phylogeography

✓ Reconstructing ancestral sequences

✓ Some common mistakes in tree interpretation

In this chapter we take a more detailed look at how to read trees and what they tell us. Perhaps more importantly, we also look at how not to read trees, and at what trees do not tell us: although the concept of tree is relatively simple, mistakes in tree interpretation are surprisingly frequent, even among professional biologists. It is thus of direct practical importance to study these pitfalls, to try to avoid them.