Estimating Divergence Dates Some practical problems: - Can be a steep learning curve - New methods...
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Transcript of Estimating Divergence Dates Some practical problems: - Can be a steep learning curve - New methods...
Estimating Divergence Dates
Some practical problems:
- Can be a steep learning curve
- New methods outstrip supply of software
- Suitable datasets hard to come by
Some rewards:
- Gain a better understanding for phylogenetic methodology
- Add a new dimension to your analyses
- Address some really cool questions!
Paleocene
Cretaceous
Late Cretaceous
Early Cretaceous
Late Jurassic
157ma ±
146ma ±
97ma ±
65ma ±
Modern Birds
‘Ratites’ and
tinamousNeognathae
Neornithes
Archaeopteryx
Paleognathae
The Radiation of Modern Birds
Feduccia, 1995Tertiary ‘big bang’
Did modern birds survive the K-T boundary?
Modern Birds
Fossil EvidenceBird
Modern birds much older - Gondwanic origin?
Molecular data
Modern Birds
Bird
KT
65 ma
Modern Birds
Fossil EvidenceBird
KT
65 ma
What about their parasites?
Younger than their
hosts?
Parasitic lice
Molecular dataLouse
Modern Birds
Fossil EvidenceBird
KT
65 ma
What about their parasites?
As old as their hosts?
Parasitic lice
Molecular dataLouse
Modern Birds
Fossil EvidenceBird
KT
65 ma
What about their parasites?
Older than their hosts?
Parasitic lice
Molecular dataLouse
Did modern birds & their lice survive the K-T boundary?Did modern birds & their lice survive the K-T boundary?Did dinosaurs have lice?
Part 1 Part 2
http://darwin.zoology.gla.ac.uk/~vsmith/temp/rates/
Or get the files from my USB flash drive
Part 1: (Qdate) Mac OS Classic or MS Windows
Part 2: (r8s) Mac OSX only
Files available at:
Quartets
All dating methods require:
- Calibration points
- Estimates of genetic divergence
- “Some” estimate of phylogeney
Ordinalrelationships of birds unknown!
Quartets
F Corvidae
F Turdidae
F AnatidaeF Meleagrididae
Earliest fossils
Genetic
divergence
Genetic
divergence
Divergence time estimatedfrom calibrated evolutionaryrates of distantly related pairs of taxa.
Divergence date
- Tree topology not in question- No assumptions needed
(two orders are compared at a time)about rate constancy - maybe?
- Estimate across multiple quartets
Fossil Lice
Psocoptera
Menacanthus /Menopon - complex
Ricinidae
Laemobothriidae
Boopiidae
Austromenopon- complex
Dennyus- complex
Colpocephalum- complex
• Collected Eckfeld maar near Eifel, Germany
• Middle Eocene (Middle Lutetian, 44.3±0.4 Ma)
• First fossil louse
• Completes ordinal representation of fossil insects
• Excellent preservation
• Phylogenetic affinities with modern feather lice
• Parasite of Anseriformes or Charadriiformes
• Crown group position
• Suggests lice are very old
• Points to a long coevolutionary history with birds
• Useful molecular calibration point
Wappler, Smith & Dalgleish, Proc.R.Soc., 2004.
Cospeciation Events
Constraints
Min. Age 44 ma
Louse Fossil
Combined ML
0.1
(18s, COI, EF1-)
Dove-Louse Cospeciation
Age Fixed 19.8 ma
Rhea/Ostrich-Louse Cospeciation
Age Fixed 60 ma
Primate-Louse Cospeciation
Age Fixed 4.5 ma
Amblyce
raIsch
noce
raAnoplu
ra
Rhyn.
Louse Phylogeny (unsmoothed)
Host Implications
2-300ma ?