W&M ScholarWorks Undergraduate Honors Theses Theses, Dissertations, & Master Projects 5-2009 Phylogenetic relationships and morphological changes in Venericardia on the Gulf Coastal Plain during the Paleogene Kate McClure College of William and Mary Follow this and additional works at: https://scholarworks.wm.edu/honorstheses Recommended Citation McClure, Kate, "Phylogenetic relationships and morphological changes in Venericardia on the Gulf Coastal Plain during the Paleogene" (2009). Undergraduate Honors Theses. Paper 297. https://scholarworks.wm.edu/honorstheses/297 This Honors Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Undergraduate Honors Theses by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Table of Contents List of Figures……………………………………………………………………………...3 List of Tables.……………………………………………………………………………...4 Abstract………………………………………………………………………………….…5 Introduction………………………………………………………… ………………….….6 Background Venericard Biology ………………………………………… ……………………..7 Taxonomic Classification ………………………………………………………...13 Paleogene Molluscan Fauna on the U.S. Gulf Coastal Plain ………… ………...17 Paleogene Climate ……………………………………….……… ……………....18 Geologic Setting on the U.S. Gulf Coastal Plain …………………… …………..21 Methods Species and Specimen Selection ………………………………………… …….…25 Phylogenetic Data Collection ………………………………………… …………28 Phylogenetic Analysis ………………………………………….... ………………29 Landmark Collection …………………………………………………… …….....30 Morphospace Analysis ….……………………………………………… …….….32 Results and Discussion: Phylogenetics General Phylogenetic Results ………………………………….. ……………….32 Outgroup Species …………………………………..... …………………………33 North American and European Venericards ………………………………… ....36 Alticostate and Planicostate Venericards …………………………………. …...38 Venericard Subgenera ……………………………….….. ………………………41 Phylogeny through Time ………………………………….. …………………….44 Results and Discussion: Morphometrics Defining Principal Component Axes ………………………………………….. ...46 Alticostate and Planicostate Venericards in Morphospace ………………… …..57 Venericard Subgenera in Morphospace ……………………………… …………59 Venericard Morphology through Time ……………………………… …………..62 Phylogeny in Morphospace ………………………………….. ………………….71 Conclusions…………………………………………………………………… …………76 1 Acknowledgments………………………………………………………………………..77 References Cited…………………………………………………………………………78 Appendix A. Phylogenetic Character Descriptions ……………………….……………….83 B. Phylogenetic Data …………………...................……………….…………..90 C. Interior Specimens ……..…………………………………………………….93 D. Cross-Sectional Specimens ….……………………………………………...101 E. Interior Landmark Data……….……………………………………………109 F. Cross-Sectional Landmark Data... …..……………………….…………….141 2 List of Figures 1. Global venericard occurrences...........………………………………….……...…….9 2. Alticostate and planicostate ornamentation…………………….…................ …….11 3. Burrowed bivalve.………………………………………..……………......... …….12 4. Venericard subgenera.…………………………………………….………....... …..16 5. World during the Early Eocene ………………………………………................. ..19 6. Paleogene temperature reconstruction.…………………………………..….......... 20 7. Paleogene paleogeography on the U.S. Gulf Coastal Plain..……..…….……....... .22 8. Stratigraphic column.……………………………………..……........... …………..23 9. Stratigraphic ranges of selected venericard species……...………...... ……………27 10. Interior landmarks.…………………………………..……………….. …………..31 11. Cross-sectional landmarks.………………………...…………...…………. ……..31 12. Phylogeny of GCP ingroup………………………..……...………………. ……...34 13. Phylogeny of GCP and European species.……………...………………. ………..35 14. Phylogeny with continent indicated………………...………………....... ………..37 15. Phylogeny of GCP ingroup with external ornament indicated.…….............. ……39 16. Phylogeny of GCP and European ingroup with external ornament indicated.... ....40 17. Phylogeny of GCP ingroup with subgenera indicated………………….. ………..42 18. Phylogeny of GCP and European ingroup with subgenera indicated….......… …..43 19. Phylogeny through time…………………………………………………….……..45 20. Interior PC1 loadings.…………………………………………………....... ……..50 21. Interior PC1 2-D shape deformation…………………………………..…....... …..50 22. Interior PC2 loadings ………………………………………………....... ………..51 23. Interior PC2 2-D shape deformation …………………………........…… ………..51 24. Interior PC1 and shell shape………………………………………….…. ………..52 25. Interior PC2 and shell shape…………………………………………….. ………..52 26. Cross-sectional PC1 loadings……………...…………………………. …………..53 27. Cross-sectional PC2 loadings…………………...……………………. …………..53 28. Cross-sectional PC2 2-D shape deformation…....………………….… …………..54 29. Cross-sectional PC2 and shell shape…………...…………………...... …………..55 30. Interior morphospace…….……………………...……………………. …………..56 3 31. Cross-sectional morphospace…………………...……………………. …………..56 32. Species averages of alticostates and planicostates: interior...……………... ……..58 33. Species averages of alticostates and planicostates: cross-sectional…….. ………..58 34. Species averages of subgenera: interior……………………………........ ………..60 35. Species averages of subgenera: cross-sectional.……………………... …………..60 36. Interior morphospace through time ………………………………...……………..63 37. Cross-sectional morphospace through time …………………………..... ………..64 38. PC values across climate shift…………………………………...…….... ………..68 39. Interior PC1 values and temperature…………………………...……...... ………..69 40. Cross-sectional morphospace through time …………………………..... ………..70 41. Phylogeny in morphospace: interior………………………...…………... ………..72 42. Phylogeny in morphospace: cross-sectional………………...…………... ………..73 43. Phylogenetic and morphometric distances between species: interior…... ………..74 44. Phylogenetic and morphometric distances between species……………. ………..75 List of Tables 1. Venericard species……………...…………………………………….…....... …….26 2. Interior landmark eigenvalues…………………….…………….…............... …….47 3. Cross-sectional landmark eigenvalues……….…..………………………..... …….48 4. T-tests of alticostate subgenera PC value…………………….………...…....... …..61 5. T-tests of PC values before and after the PETM and EOT………………............ ..67 4 Abstract The bivalve genus Venericardia is abundant and exceptionally well-preserved on the U.S. Gulf Coastal Plain during the Paleogene. The climate was extremely variable during the Paleogene, allowing the system to serve as a proxy for modern climate change. The primary goal of this research was to quantitatively reconstruct the phylogenetic relationships among venericard species and to explore patterns in venericard morphology. A phylogeny was produced from 70 qualitative multi-state characters applied to over 37 species and analyzed using a parsimony-based approach. This phylogeny identified the major clades of venericards that occur in Paleogene units along the Gulf Coastal Plain, as well as their relationships to European venericards. The phylogenetic framework was applied to investigate the evolution of external ornamentation and the validity of proposed subgenera. Landmark data were collected via digital images of the internal and cross-sectional orientations of right venericard valves and used to explore the morphometric relationships among hypothesized groups. Finally, the timing of phylogenetic events and morphometric changes were compared with climate shifts. The phylogeny demonstrates that alticostate venericards form a monophyletic group within the venericard genus. None of the proposed venericard subgenera are monophyletic, although European and North American venericard species are closely related. The interior and cross-sectional morphospaces indicate that alticostate and planicostate venericards are morphometrically separate and that the proposed subgenera are all morphometrically distinct. Venericard diversity increased after the Paleocene- Eocene Thermal Maximum, although there is no significant morphological change across the climate shift. After the Eocene-Oligocene Transition, venericards suffered an 5 extinction and became more globose in shape. These patterns could suggest that venericard morphology responds more strongly to temperature decreases than to increases. Introduction The world’s climate is shifting at an unprecedented rate and we have little idea how this change will affect the evolution and ecology of living animals. Although the current climate shift is the most dramatic within human history, it is not the only example of rapid climate change in the history of life on earth. The global climate was also extremely variable during the Paleogene (66-23.7 Ma) and included several instances of drastic increases and decreases in temperature (Bains et al., 2000; Ivany, Lohmann and Patterson, 2003; Ivany et al., 2004), which makes it a useful proxy for modern climate change. Additionally, members of the Venericardia genus of bivalves were very abundant throughout the Paleogene, and their fossil record is remarkably complete (Verastegui, 1953; Heaslip, 1968), making them an ideal taxon for studying the effects of Paleogene climate shifts. However, before the genus can be used to predict the future we need a more comprehensive understanding of the evolution of its component species. Therefore, the primary goal of this project is to quantitatively construct a phylogenetic tree illustrating the evolutionary relationships among major clades of venericard bivalves. The focus is on the U.S. Gulf Coastal Plain during the Paleogene, although the study also includes contemporaneous European