Presentation on theme: "Estimating Divergence Dates Some practical problems: - Can be a steep learning curve - New methods outstrip supply of software - Suitable datasets hard."— Presentation transcript:
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 tinamous Neognathae Neornithes Archaeopteryx Paleognathae The Radiation of Modern Birds Feduccia, 1995 Tertiary big bang
Did modern birds survive the K-T boundary? Modern Birds Fossil Evidence Bird Modern birds much older - Gondwanic origin? Molecular data Modern Birds Bird KT 65 ma
Modern Birds Fossil Evidence Bird KT 65 ma What about their parasites? Younger than their hosts? Parasitic lice Molecular data Louse
Modern Birds Fossil Evidence Bird KT 65 ma What about their parasites? As old as their hosts? Parasitic lice Molecular data Louse
Modern Birds Fossil Evidence Bird KT 65 ma What about their parasites? Older than their hosts? Parasitic lice Molecular data Louse Did modern birds & their lice survive the K-T boundary? Did dinosaurs have lice? Part 1Part 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 Ordinal relationships of birds unknown!
Quartets F Corvidae F Turdidae F Anatidae F Meleagrididae Earliest fossils Genetic divergence Genetic divergence Divergence time estimated from calibrated evolutionary rates 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 Amblycera Ischnocera Anoplura Rhyn. Louse Phylogeny (unsmoothed)