Question
• What is Taxonomy?
• What is taxonomy/systematics?
• Classification with context
• Phylogeny - systematics = relationships
• Why is this Important?
Classification
• Natural Groups
• Carl Linnaeus - 1700’s
• Hierarchical classification scheme
– Kingdom
• Phylum
– Class
» Order
» Family
» Genus
» Species
• Species = binomen (two-part name)
– Homo erectus
Describing Species
• In order to name a new species - must publish description
• Formal protocol - ICZN rules
• description must be published (see box 4.1 p. 59-61)
• a picture should be included though not mandatory
• must use a Latin Binomial Name
• Law of Priority and senior and junior synonyms
• specimens of the species must be put in a museum so other workers can
have access to them.
– Types
Describing Species
• Specimens
– holotype -- representative - important features of the species
– syntypes -- a group of specimens
– paratypes -- show variation within the species
– . . . many other 'types of types'
Systematics/Phylogenetics
• phylogeny = history of evolutionary descent; evolutionary genealogy
• Does taxonomy reflect phylogeny?
• Classification = convenience
• What character traits are important?
• Why is phylogeny important?
• Understanding -
– Diversification and extinction
– Common ancestry
Systematics/Phylogenetics - Approaches
• How do you reconstruct phylogeny?
• Classical Phenetics or Evolutionary Systematics (traditional approach)
• a few diagnostic characters are selected
• requires a life long dedication
• problems:
– - subjective
– - not testable or repeatable
• examples: Archaeopteryx placed in C-Aves based on one character, feathers
• C-Bivalvia subdivided on basis of hinge structure (for paleontologists)
or gill structure (for biologists)
Systematics/Phylogenetics - Approaches
• Phenetics or Numerical Taxonomy
• a response to the problems of classical method
• all characters considered; data intensive: uses only quantifiable characters
• computer compares all combinations; get a dendrogram; coefficient of
similarity (cluster anylysis)
• problems:
• hard to do; tedious
• doesn't weigh characters; all have equal importance
• Not truly objective - coding characteristics
• no consideration of homology; some characters could be due to convergence
Question
• What are the primary differences between classical phenetics and numerical
taxonomy?
Phylogeny
• Phylogeny - evolutionary relationships (ancestor/descendant)
• Symmetry
Phylogeny
• Embryology
Systematics/Phylogenetics - Approaches
• Cladistics or Phylogenetic Method (Hennig, 1966)
• Objective, testable, evaluates characteristics, only evolutionary history
• Common ancestry not ancestor/descendent relationships - nodes
• Sister groups
Cladistics
• Basic procedures
• characters and character states
– select characters and define character states
• homology; testing for homology - evolutionary novelties
• Synapomorphies - shared derived characteristics
• Synplesiomorphies - shared primitive characteristics
• character polarity (to determine primitive vs. derived)
Cladistics
• How do you choose character polarity
– Outgroup method
• principle of parsimony
• Initial problem = stratigraphic position = not important
Cladistics
• Cladistics exercise
• Do phenetics classification
• Construct a data table and a cladogram