Understanding Trees

Pre-test Which mammal is the pig more closely related to, cow or camel? Which mammal here is the most primitive? Fig. 4.8b

Common ancestor Root of the tree Nodes Terminal taxa (tips) Branches

Phylograms and Cladograms

Trees can be built for extinct organisms…

Trees can include lineage “persistence”

Some trees show timing of events

Most trees today are built for extant organisms only…

Tree Rules 1. Read the nodes, remember they swivel 2. Bifurcation rule 3. Monophyly snip rule 4. Sibling ≠ Ancestor 5. Sister lineage snip rule and ages

1. Read the nodes, remember they swivel! Don’t read left to right or top to bottom Read the nodes, and the nodes swivel

Read the nodes ABCD e f g For cladograms, some information about timing (e and f after g)

For phylograms, a little more information about timing

This tree is ladderized right… Swivel the nodes to make it ladderized left Redraw it with lungfish at the top

Assignment

2. Bifurcation Rule Can only have one divergence event at a time. Can’t have two divergence events at the same time (snap two fingers at once)

Breaking the Bifurcation Rule: Hard polytomies and Soft polytomies Cichlids