April Wright - SVP 2014
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Transcript of April Wright - SVP 2014
Fossils-only tip-dating of deinonychosaurian
theropodsApril M. Wright
Nicholas J. MatzkeGraeme T. LloydDavid W. Bapst
Can we use fossils-as-tips methods to co-estimate phylogeny and divergence dates in
the absence of molecular data?
Theropods as a test case for tip-dating● Controversial● Implications for the evolution of flight● Well-documented ages and relationships
among taxa in the tree
Applying tip-dating methods
● Used Xu et al. matrix● 89 taxa, 389 morphological characters
○ Missing data ranges between ~5% and ~85% per taxon
○ 363 characters from Hu et al. 2009, 10 added by Xu et al.
○ Mix of cranial and post-cranial characters
Applying tip-dating methods
● Dates associated with every terminal in the matrix○ Both a minimum and a maximum age
Applying tip-dating methods
● Dates associated with every terminal in the matrix○ Both a minimum and a maximum age
● BEAST2 and MrBayes tip dating○ Both methods use the dates of the terminal taxa
instead of calibration points○ Both use Lewis’ 2001 Mk model
Applying tip-dating methods
● BEAST2○ Birth-death serial sampling prior: Allows for
speciation and extinction in tree for data sampled from multiple time-points
● MrBayes○ Uniform prior on clock trees○ Ingroup date calibration
Applying tip-dating methods
● BEAST2○ More explicit process-driven model
● MrBayes○ More vague with respect to biology and taphonomy
MrBayes
● We were unable to obtain a topology with dates in which we had confidence○ Well-known clades being broken up○ Unrealistic dates that contradict the weight of
existing evidence
Conclusions
● Tip-dating is a viable method for estimating divergence dates○ Tip-dating can be performed with fossil-
only datasets● BEAST returns a topology and dates that
correspond well to known information about deinonychosaurian and avian relationships