Phylogenetic inferenceRead 26.1-26.3Cladistics is a method of hypothesizing relationships among organisms
Phylogenetic inferenceefinitions: Apomorphy: Derived characterSynapomorphy: Shared derived characterPlesiomorphy: ancestral characterA B C D apomorphysynapomorphyplesiomorphy
CLADOGRAM: is comprised of branches and nodes EABCDEABCD
CLADOGRAM: is comprised of branches and nodes EACDBC
Phylogenetic inferenceRead 26.1-26.3Phylogenetic trees are built from “characters”• characters can be morphological, behavioral, physiological, or molecular.• there are two important assumptions about characters used to build trees:1. they are independent2. they are homologous
2. Any group of organisms is related by descent from a common ancestor. Homology vs. Convergent Evolution (homoplasy)
3. There is a dichotomous branching pattern of lineage-splitting.
•Choose the taxa whose evolutionary relationships interest you•Choose an outgroup- a taxon outside the clade•Determine the characters and character states •Determine the polarity of characters•Figure out the order of evolution for each character. •Group taxa by synapomorphies •Work out conflictsReconstructing trees: A step by step method