1. Classification and Phylogenetic Relationships
Early natural historians classified organisms based on shared features
Now we seek to understand how organisms features are related to phylogenetic relationships, descent from a common ancestor
Classifications and relationships change over time, as we learn more details and test hypotheses

2. Fig pg 231

3. Species Concepts How to recognize species Morphological species
Biological species
Evolutionary species

4. Morphological Species
Assemblages of individuals with morphological features in common
Separable from other assemblages by discontinuities in a number of features
Numerical (phenetic) taxonomy
Incorporates statistical tools to identify taxonomic distinctions
High statistical correlation of large number of characters distinguishes groups

5. Biological Species From Buffon Sibling species Polytipic species
A sexually interbreeding (or potentially interbreeding) group, separated from other species by reproductive isolation
Sibling species
Nearly identical but do not normally cross-fertilize
Polytipic species
Multiple geographic subspecies, can exchange genes if come into contact
Difficulties
Allopatric populations
Subjective scale of success for interbreeding
Cannot test fossils
Does not apply to plants
Horizontal gene transmission between different species

6. Fig 11.2 pg 233
Evolution in the Genus Geum, Evolution 13, by W. Gajewski. Reprinted by permission.)

7. Evolutionary Species Evolutionary isolation
Not dependent upon sexual isolation
A species concept that incorporates change over time
Stage when group has attained complete separation subjective

8. Phylogeny Origin of new species Phyletic versus Cladogenesis
Phyletic evolution
Changes within a single lineage
Phylogenetic branching, Cladogenesis
Splits and divisions result in multiplication in number of species
The more a group shares common inherited attributes, the more likely their descent from a common ancestor
Fig 11.4 pg 235

9. Phylogeny Shared attributes can occur by several ways Homology
Feature is shared because species derived from common ancestor
Homoplasy
Common feature but ancestor was different
Similar adaptation from different starting points
Parallelism
Immediate common ancestor was different
Convergence
Lineage has been separated for considerable time

10. Homology A phenotypic feature that is shared due to common ancestry
It is critical to specify the level at which homology is designated
Genetic > Development > Morphology > Function
Serial homology
Similarities among parts of the same organism
E.g. vertebrae
Homologous features, may arise by different developmental pathways

11. Homology, Partial Homology and Percent Similarity
Homology as applied to DNA sequence similarity
Orthologous genes
Genes duplicated in different species
Paralogous genes
Genes duplicated within a species
Partial Homology, percent similarity
Early molecular workers comparing two genes might have discussed partial homology, percent similarity between to genes
No longer accepted
Homologous or not homologous

12. Homology and Constructing Phylogenetic Trees
Homology is the basis for constructing phylogenetic trees
Monophyletic groups
Individuals share a common ancestor
Polyphyletic groups
Individuals in do all share a common ancestor
Convergence
Fig 11.8 pg 240

13. Phylogenetic Trees Phylogeny is something that happened
Classification is an arrangement of its results
Ideal multi-limbed phylogenetic tree would include all ancestral populations
Impossible
Most species are unknown (fossils)
Unable to compute, to complex

14. Phylogenetic Trees Taxon (plural taxa)
Unit of classification, whether species, genus, order,…
Groups might not always be monophyletic in different classification schemes
Fig 11.9 pg 241

15. Cladistics, Phylogenetic Systematics
Willi Hennig ( )
Separation of plesiomorphic (ancestral) characters from apomorphic (derived) characters
Monophyletic groups
Defined by synapomorphic (shared derived) characters
Evolutionary steps marked by dichotomous branching of sister taxa
Paraphyletic groups
Groups that includes some descendents of a common ancestor, but not all
Parsimony method
Preferred phylogenetic tree has least number of steps

16. Cladistics, Phylogenetic Systematics
Fig pg 243