Key Concepts in Phylogeny inference
Key points
• Evolutionary trees do not show everything
• Evolutionary trees can be drawn in various styles
• Evolutionary trees are hypotheses
Tree thinking
• Definition of syn apo morphy:
• Synapomorphy = a trait that certain species have that no
other species has
• Synapomorphies identify monophyletic groups
• Shared
• Derived
• Character
Terminology in phylogenetics
• Homologous traits
• Homoplasy
• Apomorphy – (separate form) – derived character
• Plesiomorphy - (near form) – ancestral character
Terminology in phylogenetics
•
Synapomorphy, based on a
homologous trait
Monophyletic group (or lineage,
clade): an ancestor and all of its
descendants = purple
Frogs
Limbs
•
•
Paraphyletic group: an ancestor
and some, but not all, of its
descendents = grey
Polyphyletic group: share a trait
that didn’t exist in the common
ancestor = yellow
Lactation
Salamanders
Mammals
Amniotic
egg
Scales
Warm blood
Lizards, snakes
Turtles
Crocodiles
Birds
Warm blood
What is the value of an outgroup?
Parsimony
•
Fewest evolutionary changes in characters of interest
Polytomy
•
Uncertainty about branching order
•
Wiley, E. O. and Johnson, G. D. 2010. A teleost classification based on monophyletic groups. In J. S. Nelson, H.-P.
Schultze, & M. V. H. Wilson (eds) Origin and Phylogenetic Interrelationships of Teleosts. Pp. 123-182, Verlag Dr.
Friedrich Pfeil, München, Germany.
Using phylogenies for hypothesis testing
River dolphins
Hrbeck et al. 2014