The Great Clade Race Long long ago in a place far far away eight runners AH met in the woods for a foot race All the runners began the race at a single starting point but at various points the course forked Each series of forks led to a separate finish line at the other end of th ID: 614733
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Slide1
Building treesSlide2
The Great Clade Race
Long, long ago, in a place far, far away, eight runners (A–H) met in the woods for a foot race. All the runners began the race at a single starting point, but, at various points, the course forked. Each series of forks led to a separate finish line at the other end of the woods. At each fork, runners chose which path to take.
To keep track of the race, each runner carried a card that was stamped at check-in stations distributed at various points along the paths. Each runner had his or her card stamped at each check-in station they passed.
Use these cards to try and reconstruct the course of each runner and the placement of check-in stations. Slide3
The Great Clade Race
1. All runners completed the race, i.e., nobody stopped midday along a path.
2. When the paths split, they forked into two new paths, not three or more.
3. Once paths diverged, they never reunited. 4. Check-in stations were located between forks in the paths. Slide4
Bony Ray Amniotic
Skeleton fins Egg Lactation
Perch 1 1 0 0
Guppy 1 1 0 0
Shark 0 0 0 0
Cat 1 0 1 1
Dog 1 0 1 1
Lizard 1 0 1 0 Slide5
Terms for
cladistic
tree building
CharacterCharacter stateAncestral character state (Plesiomorphic)Symplesiomorphy
Derived character state (Apomorphic)
Synapomorphy
AutapomorphySlide6
Synapomorphies are marked
Examples of symplesiomorphies?Slide7
How can we determine synapomorphy vs. symplesiomorphy?Slide8
Outgroups
Outgroups are the most common method for rooting trees
Outgroup criteria
1. “Outside” the group of studyClosely related enough to be informative