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Fixations along phylogenetic lineages. Phylogenetic reconstruction: a simplification of the evolutionary process. Cladists and pheneticists. Anatomy of a phylogenetic tree. Edges and nodes. Depictions of phylogenetic trees. Slanted Cladogram. Rectangular Cladogram. Phylogram. Circle tree.
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Phylogenetic reconstruction: a simplification of the evolutionary process
Depictions of phylogenetic trees Slanted Cladogram Rectangular Cladogram Phylogram
Circle tree Unrooted cladogram Unrooted phylogram
Depicting trees with branch lengths Ultrametric tree Unconstrained tree Time Time Present
Branch lengths and phylogenetic trees Unequal branch lengths Ultrametric trees
“One should not increase, beyond what is necessary, the number of entities required to explain anything.” Parsimony, Hennig and Occam’s razor William of Ockham (ca. 1285-1349) Synapomorphies designate clades… But what if synapomorphies are reversed? Willi Hennig
Long-branch attraction p, q probability of observing a change between nodes or From node to tip
Parsimony is consistent when p2 < q(1-q) The “Felsenstein zone”
Parsimony: pros and cons Pros: Simple and fast (sometimes) Cons: Depends on a very simple ‘model’ of substitution Does not estimate branch lengths well Susceptible to long-branch attraction