Classification and phylogeny

Early classification schemes

Fish & whales

Flies & birds

Frogs & alligators

Squirrels & monkeys

Early classification schemes

Fish & whales

Flies & birds

Frogs & alligators

Squirrels & monkeys

Swim in water

Fly in air

Crawl in mud

Climb in trees

Early classification schemes

Honeybee:

Apis pubescens, thorace subgriseo, abdomine fusco, pedibus posticis glabris utrinque margine ciliatis

Apis mellifera

Early classification schemes

Honeybee:

Apis pubescens, thorace subgriseo, abdomine fusco, pedibus posticis glabris utrinque margine ciliatis

Apis mellifera

Linnaeus introduced: binomial nomenclaturehierarchical classification

Hierarchical classification

Kingdom

Phylum

Class

Order

Family

Genus

Species

How the leopard got its spots

Phylogenetic trees are a visual representation of the fact that species are related by descent from a common ancestor

Phylogeny

Anagensis (phyletic evolution) - successional changes within a single lineage

Cladogenesis (phylogenetic branching) - splits along ancestral line that cause species multiplication (ie. appearance of new clades, clusters of species)

homology - same feature in different species, derived from common ancestor

parallelism - similar feature occurs in different species, but common ancestor was different

convergence - similar feature arose independently in different species

Monophyletic - organisms derive from a single ancestral population

Paraphyletic - does not include all descendents from the ancestral population

Polyphyletic - organisms arrived independently at a particular grade of organization

Phylogeny

Monophyletic Paraphyletic

Paraphyletic groups

Phenetics - applies numerical taxonomy to arranging groups into genera & higher ranks

Cladistics - every significant evolutionary step marks a dichotomous branch

Evolutionary classification - incorporates genealogical relationship between groups with evolutionary distance

Phylogeny

Character a b c d1 1 1 0 02 1 1 0 03 1 1 1 04 1 1 1 05 1 1 1 06 1 1 1 07 0 1 0 08 0 1 0 09 0 1 0 010 1 0 1 011 1 0 0 1

Phenetics

a b c da - 6 7 3b - 4 0c - 5d -

a c b d

sim

ilari

ty

Phenetics

B = (BA + BC)/2B = 5D = 0

Phenograms do not necessarily represent phylogenetic relationships

Similarity - number of character states 2 species share

Relationship - how recently they diverged from a common ancestor

Phenetics

Cladistics

Character a b c d1 1 1 0 02 1 1 0 03 1 1 1 04 1 1 1 05 1 1 1 06 1 1 1 07 0 1 0 08 0 1 0 09 0 1 0 010 1 0 1 011 1 0 0 1

0 pleisomorphic1 apomorphic

Cladistics

a b c da - 6 4 0b - 4 0c - 0d -

a b c d

12

345

6

789

Synapomorphies arise at evolutionary branch points

Taxonomy

Characters must be independent

homologous

Evolutionary relationships only revealed by shared, derived traits

= synapomorphies

Terminology

plesiomorphy

symplesiomorphy

apomorphy

synapomorphy

autapomorphy

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

2 homoplasy is common in evolution

Convergent evolution (convergence)

Parallel evolution (parallelism)

Evolutionary reversals

Homoplasy

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

2 homoplasy is common in evolution

3 rates of character evolution differ

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

2 homoplasy is common in evolution

3 rates of character evolution differ

4 evolution is often gradual

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

2 homoplasy is common in evolution

3 rates of character evolution differ

4 evolution is often gradual

5 characteristics often owe their change in form to change in function

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

2 homoplasy is common in evolution

3 rates of character evolution differ

4 evolution is often gradual

5 characteristics often owe their change in form to change in function

6 phylogenetic analysis documents evolutionary trends

Principles of evolutionary change, inferred from systematics

1 homologous features are derived from common ancestors

2 homoplasy is common in evolution

3 rates of character evolution differ

4 evolution is often gradual

5 characteristics often owe their change in form to change in function

6 phylogenetic analysis documents evolutionary trends

7 most clades display evolutionary radiation

Cladistics

Character a b c d1 1 1 0 02 1 1 0 03 1 1 1 04 1 1 1 05 1 1 1 06 1 1 1 07 0 1 0 08 0 1 0 09 0 1 0 010 1 0 1 011 1 0 0 1

0 pleisomorphic1 apomorphic

Cladistics

a b c da - 6 4 0b - 4 0c - 0d -

a b c d111110

10