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Home , Clade, Phylogenetics

Lecture 2 of

1. Phylogenetic

2. General fish

3. Molecular systematics & Genetic approaches Charles & Alfred Russel Wallace

All are related through

1809 - 1882 1823 - 1913 (1913 – 1976)

• Hennig developed cladistic method to infer relatedness

• Goal is to correctly group ancestors and all their descendants

A :

1. All individuals descend from a single ancestor

2. All descendents of that ancestor are part of the clade Cladistics (a.k.a Phylogenetic Systematics)

Fundamental approach • divide characters into two groups

• Apomorphies: more recently derived characteristics

• Plesiomorphies: more ancestral, primitive characteristics

• Identify Synapomorphies (shared derived characteristics)

• group by synapomorphies Cladistics (a.k.a Phylogenetic Systematics)

Synapomorphy of rockfish, gills bichir, and ? jaws

bony skeleton

swim bladder

Bichir Rockfish Sharks Hagfish Cladistics (a.k.a Phylogenetic Systematics)

eyes “Ancestral” and “derived” are gills relative to your focal group jaws

bony skeleton

swim bladder

Bichir Rockfish Sharks Lamprey Hagfish Cladistics (a.k.a Phylogenetic Systematics)

Monophyletic (aka clade): all taxa are descended from a common ancestor that is not the ancestor of any other group (every taxa descended from that ancestor is included)

examples? Cladistics (a.k.a Phylogenetic Systematics)

Paraphyletic: the group does not contain all species descended from the most recent common ancestor of its members

examples? Cladistics (a.k.a Phylogenetic Systematics)

Polyphyletic: taxa are descended from several ancestors that are also the ancestors of taxa classified into other groups

examples? Problems with Traditional Cladistics • traits evolved due to convergence

- keel: stabilizes tail at high speeds Problems with Traditional Cladistics Statistically inconsistent • can lend more support for the wrong answer

Bernal et al. 2001 Problems with Traditional Cladistics Unequal rates • lineages can evolve at different rates

Cyprinidae Molecular Systematics & Genetic Approaches

Compares similarities and differences in DNA sequences • identify informative sequences (aka synapomorphies)

Different parts of the genome evolve at different rates • choose appropriate sequences to compare

Address questions about & evolutionary history that traditional systematics can not African & the Great African Rift Lakes

Lake Victoria ~400-500 spp.

Lake Tanganyika

~180-250 spp.

Lake Malawi ~700-1000 spp. Parallel or ?

omnivore

vegetarian vegetarian

piscivorous piscivorous

carnivore carnivore generalist generalist

omnivore omnivore Lake Tanganyika Lake Malawi

3 common ancestors Convergent evolution Lake Tanganyika Lake Malawi

1 common ancestor 1 common ancestor Parallel Evolution

Predicted Result Convergent evolution

Predicted Result

Lake Tanganyika

Lake Malawi Molecular tree based on cytochrome b sequences

100 Victoria Haplochromines

100 Malawi Haplochromines Group A

Malawi Haplochromines Group B 100

100 Astatoreochromis Tanganyika Julidochromis Tanganyika Lamprologus

Myrs 6 4 2 0 Calibration in Sharks • and geologic events

• Calibrate sequence divergence

• Establish molecular clock

• ~7-8x slower than

Martin et al 1992 Evolution of Endothermy - or convergence? Molecular Systematics & Genetic Approaches

Gene trees vs. species trees • trees don’t necessarily reflect the species tree

The more gene trees you sample, the more likely you converge on the species tree

red = gene tree blue = species tree Surfperches (Embiotocidae)

25 Surfperches (Embiotocidae)

Longo & Bernardi 2015 Longo & Bernardi 2015 Surfperches (Embiotocidae)

Bernardi & Bucciarelli 1999 Surfperches (Embiotocidae)

LongoLongo & &Bernardi Bernardi 2015 2015