Ecological, Taphonomic, and Paleoecological Dynamics of An
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ECOLOGICAL, TAPHONOMIC, AND PALEOECOLOGICAL DYNAMICS OF AN OSTRACODE METACOMMUNITY A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Andrew V. Michelson August, 2012 ECOLOGICAL, TAPHONOMIC, AND PALEOECOLOGICAL DYNAMICS OF AN OSTRACODE METACOMMUNITY Andrew V. Michelson Dissertation Approved: Accepted: _________________________ ___________________________ Advisor Department Chair Dr. Lisa E. Park Dr. Monte E. Turner _________________________ ___________________________ Committee Member Dean of the College Dr. Francisco B.-G. Moore Dr. Chand Midha _________________________ ___________________________ Committee Member Dean of the Graduate School Dr. Jean J. Pan Dr. George R. Newkome _________________________ ___________________________ Committee Member Date Dr. John M. Senko _________________________ Committee Member Dr. Alison J. Smith ii ABSTRACT The modern synthesis of paleontology with evolutionary biology has successfully integrated population ecology into the study of the fossil record. While it may prove impossible to measure and account for the important processes that structure communities through time, the integration of community ecology into paleoecology remains to be done to further the modern synthesis. This dissertation attempts to integrate community ecology into the study of a lacustrine ostracode metacommunity across space today and through the mid Holocene on San Salvador Island, Bahamas. Patterns of community change across space today are investigated by comparing the live/dead agreement in taxonomic composition and rank-abundance of species in seven lakes. This taphonomic study establishes that live/dead agreement of ostracode assemblages is high in all lakes save one. Therefore, sampling of death assemblages, as is common in many paleolimnolgical studies, can be used to investigate changes in alpha and beta diversity of assemblages across time and space. Death assemblages were then sampled from thirty-two lakes on San Salvador to investigate the metacommunity dynamics that explain patterns of beta diversity of communities. I found that beta diversity was most strongly controlled by the local environment in which communities live with the change in communities most strongly correlated with changes in a complex hydrological gradient of: conductivity, dissolved oxygen, and alkalinity. iii After establishing that the metacommunity dynamics conformed to a species sorting model, I exploited the association between ostracode assemblages and conductivity to create a statistical model that used changes in ostracode assemblages to predict changes in conductivity within individual lakes on San Salvador. This model was then applied to archives of ostracode assemblages from the mid-Holocene to today to create a record of changing conductivity through time in three lakes. The model reveals large, high-frequency fluctuations in conductivity controlled by regional changes in precipitation/evaporation ratios, controlled by similarly high frequency climate oscillations. Finally, I use the metacommunity concept of community ecology as a theoretical tool to explain how changes in communities through time are related to ecosystem dynamics. Ostracodes, as easily-dispersed organisms who respond to changes in their local environment through habitat-tracking, prove to be consistently useful proxies of environmental changes. In this way, neontological principles are successfully applied to the paleoecological record demonstrating the seamless application of community ecology to the fossil record. iv DEDICATION To my parents, Allan, Barbara, and Melonie for giving me the greatest gift, an education and to René, the wish of my heart v ACKNOWLEDGEMENTS First and foremost, I thank my adviser, Lisa E. Park. She guided this research from the start and has provided invaluable advice throughout its completion. I will forever be grateful for the many opportunities she has provided me to grow as a scientist, mentor, and teacher. I hope I will someday be as good a scientist as she is. I also thank all the members of my committee: Francisco B.-G. Moore, Jean J. Pan, John M. Senko, and Alison J. Smith. They all provided unique advice and constructive criticism. I could not have done this without them. Stephen C. Weeks deserves credit for encouraging me to become a scientist. He saw potential in me I did not know was there. Sara Bright, Mark Dalman, Emily Draher, and Emily Woodward provided enormous help collecting samples from lakes both pristine and foul. I am grateful for Tom and Erin Rothfus’ support in the field. After a full day driving around San Salvador it is comforting to know you have a warm bed and a hot meal to come home to. Tom Quick has provided innumerable hours of technical support, always with a smile and a kind word. Elaine Butcher continues to provide great support navigating through administration and organizational problems. Finally, my family René Rivera, and Allan, Barbara, Megan, Melonie, and Sarah Michelson, and have continually provided me with love and support, without which I never would have had the strength to finish this. vi TABLE OF CONTENTS Page LIST OF TABLES ………………………………………………...…………………….ix LIST OF FIGURES ……………………………………………………………...............x CHAPTER I. TAPHONOMIC DYNAMICS OF LACUSTRINE OSTRACODES ON SAN SALVADOR ISLAND, BAHAMAS: HIGH FIDELITY AND EVIDENCE OF ANTHROPOEGENIC MODIFICATION………………………………………...............1 Introduction………………………………………………………………………..2 Methods……………………………………………………………………………7 Results……………………………………………………………………………10 Discussion……………………………………………………………………..…21 II. DISCERNING PATTERN OF DIVERSITY AND BIOGEOGRAPHICAL DISTRIBUTIONS: OSTRACODE METACOMMUNITY DYNAMICS ON SAN SALVADOR ISLAND, BAHAMAS…………………………….…………..………….25 Introduction………………………………………………………………………26 Methods…………………………………………………………………………..33 Results……………………………………………………………………………38 Discussion……………………………………………………………………..…50 III. TESTING THE ASSUMPTIONS OF HIGH RESOLUTION PALEOENVIRONMENTAL INFERENCE MODELS IN AN ECOLOGICAL CONTEXT………………………………….................…………....................................59 Introduction………………………………………………………………………60 Methods…………………………………………………………………………..67 vii Results……………………………………………………………………………72 Discussion……………………………………………………………………..…78 IV. A QUANTITATIVE INFERENCE MODEL FOR CONDUCTIVITY USING OSTRACODE ASSEMBLAGES ON SAN SALVADOR ISLAND, BAHAMAS………………….………………………………………………………......99 Introduction……………………………………………………………………..100 Methods…………………………………………………………………………104 Results…………………………………………………………………………..111 Discussion………………………………………………………………………131 Conclusions……………………………………………………………………..141 REFERENCES ………………………………………………………………………...142 APPENDICIES………………………………………………………………………....155 APPENDIX A. TAPHONOMIC DATA: LIVING ASSEMBLAGES..……………....156 APPENDIX B. TAPHONOMIC DATA: DEATH ASSEMBLAGES………………...165 APPENDIX C. GEOGRAPHIC, LIMNOLOGICAL, CHEMICAL, OSTRACODE DATA FROM ALL LAKES…………………………………………………………...174 APPENDIX D. FOSSIL OSTRCODE DATA FROM SALT POND CORE ………...182 APPENDIX E. FOSSIL OSTRCODE DATA FROM CLEAR POND CORE………..184 APPENDIX F. FOSSIL OSTRCODE DATA FROM NORTH STORRS CORE…….187 APPENDIX G. PHYSICAL DATA FROM SALT POND CORE……………………195 APPENDIX H. PHYSICAL DATA FROM CLEAR POND CORE………………….197 APPENDIX I. PHYSICAL DATA FROM NORTH STORRS CORE………………..201 APPENDIX J. POTASSIUM XRF DATA CLEAR POND CORE…………………...206 APPENDIX K. POTASSIUM XRF DATA NORTH STORRS CORE……………….314 viii LIST OF TABLES Table Page 1.1 Species list of the ostracodes from this study…………………………………...….. 11 2.1 Criteria for distinguishing metacommunity models…………………………..……..31 2.2 Species list of the ostracodes from this study…………………………………...…...39 2.3 Minimum, maximum, mean, and standard deviation of measured environmental variables in all lakes………………………………………………………………...........44 3.1 The assumption of the transfer function method of paleoenvironmental reconstruction ……………………………………………………………………………………………62 3.2 Species list of the ostracodes from this study…………………………………..……73 3.3 Criteria for distinguishing metacommunity models…………………………………92 4.1 Minimum, maximum, mean, and standard deviation of measured environmental variables in all lakes……………………………………………………………….........112 4.2 Pearson's correlation (r) of measured environmental variables with the first two axes of a three-dimensional non-metric multidimensional scaling plot……………………..115 4.3 Conductivity optima and tolerances for all species………………………………...118 4.4 Performance of apparent and cross-validated statistics of the conductivity transfer function…………………………………………………………………………………124 4.5 Results of radiocarbon dating of all three cores……………………………….........126 ix LIST OF FIGURES Figure Page 1.1 Map of San Salvador Island showing lakes sampled………………………….............8 1.2 Ostracode species encountered in this study…………………………………............12 1.3 Box plot of rho in all lakes sampled…………………………………………………16 1.4 Mean rho of each lake according to its mean species richness………………………17 1.5 Taxonomic similarity (Jaccard-Chao index) and rank-abundance correlation of 112 samples of living communities and associated death assemblages………………...........18 1.6 First 2-dimensions of a 3-dimensional nonmetric multidimensional scaling ordination on the Bray-Curtis dissimilarity matrix of all samples with lakes overlain………...........19 2.1 San Salvador Island, Bahamas……………………………………………………….34 2.2 Ostracode species encountered in this study…………………………………………40 2.3 Scatter plot of Euclidean distances of Z-scores