Talk for 2014 SVP meetings

1. Fossils-only tip-dating of
deinonychosaurian
theropods
April M. Wright
Nicholas J. Matzke
Graeme T. Lloyd
David W. Bapst

2. www.slideshare.net/wrightaprilm/wright-svp2014

3. Can we use fossils-as-tips methods to co-estimate
phylogeny and divergence dates in
the absence of molecular data?

4. 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

5. Placement of Archaeopteryx

6. Placement of Archaeopteryx

7. Placement of Archaeopteryx

8. A paleontological question

9. A paleontological question

10. A paleontological question

11. A paleontological question
Archaeopteryx as
a calibration
node

12. 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

13. Applying tip-dating methods
● Dates associated with every terminal in the
matrix
○ Both a minimum and a maximum age

14. 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

15. 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

16. Applying tip-dating methods
● BEAST2
○ More explicit process-driven model
● MrBayes
○ More vague with respect to biology and taphonomy

17. } Aves
}Deinonychosauria
200 175 150 125 100 75 50 25

18. } Aves
}Deinonychosauria
200 175 150 125 100 75 50 25

19. } Aves
}Deinonychosauria
200 175 150 125 100 75 50 25

20. Placement of Archaeopteryx

21. 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

22. MrBayes
Xu et al. 2006

23. MrBayes

24. 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

25. Thanks!
● Participants
● Hillis Lab
Group
● Nadia
Fröbisch,
Jonathan
Bloch, Anjali
Goswami