Lecture 2 Phylogenetics of Fishes 1. Phylogenetic systematics 2. General fish evolution 3. Molecular systematics & Genetic approaches
Charles Darwin & Alfred Russel Wallace All species are related through common descent 1809-1882 1823-1913
Willi Hennig (1913 1976) Hennig developed cladistical method to infer relatedness Goal is to correctly group ancestors and all their descendants
Cladistics (a.k.a Phylogenetic Systematics) Fundamental approach divide characters into two groups Apomorphies: more recently derived characteristics Pleisomorhpies: more ancestral, primitive characteristics Identify Synapomorphies (shared derived characteristics) group clades by synapomorphies
Cladistics (a.k.a Phylogenetic Systematics) Synapomorphy of rockfish, bichir, and sharks? jaws eyes gills bony skeleton swim bladder Rockfish Bichir Sharks Lamprey Hagfish
Cladistics (a.k.a Phylogenetic Systematics) Sympleisomorphy of rockfish, bichir, and sharks? jaws eyes gills bony skeleton swim bladder Rockfish Bichir Sharks Lamprey Hagfish
Cladistics (a.k.a Phylogenetic Systematics) Ancestral and derived are relative to your focal group jaws eyes gills bony skeleton swim bladder Rockfish Bichir 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 Homoplasies 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 biogeography & evolutionary history that traditional systematics can not
African Cichlids & the Great African Rift Lakes Lake Victoria ~400-500 spp. Lake Tanganyika ~180-250 spp. Lake Malawi ~700-1000 spp.
Parallel or Convergent Evolution? omnivore omnivore vegetarian vegetarian piscivorous piscivorous carnivore generalist carnivore generalist omnivore omnivore
Lake Tanganyika Parallel Evolution Lake Malawi 3 common ancestors
Lake Tanganyika Convergent evolution Lake Malawi 1 common ancestor 1 common ancestor
Parallel or Convergent Evolution? Take a few minutes to draw alternative phylogenetic hypotheses for parallel and convergent evolutionary scenarios (talk to your neighbors).
Predicted Result Parallel Evolution
Convergent evolution Predicted Result Lake Tanganyika Lake Malawi
Molecular tree based on cytochrome b sequences 100 Victoria Haplochromines 100 100 Malawi Haplochromines Group A Malawi Haplochromines Group B 100 Astatoreochromis Tanganyika Julidochromis Tanganyika Lamprologus 6 4 2 0 Myrs
Molecular Clock Calibration in Sharks Fossils and geologic events Calibrate sequence divergence Establish molecular clock ~7-8x slower than mammals Martin et al 1992
Evolution of Endothermy - monophyly or convergence?
Molecular Systematics & Genetic Approaches Gene trees vs. species trees gene 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) Bernardi & Bucciarelli 1999
Longo Longo && Bernardi Bernardi 2015 2015 Surfperches (Embiotocidae)