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The Evolutionary Dynamics of Sexual Systems in Deep Time: an Integrated THE EVOLUTIONARY DYNAMICS OF SEXUAL SYSTEMS IN DEEP TIME: AN INTEGRATED BIOLOGICAL AND PALEONTOLOGICAL APPROACH A Dissertation Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Timothy Ian Astrop August 2014 THE EVOLUTIONARY DYNAMICS OF SEXUAL SYSTEMS IN DEEP TIME: AN INTEGRATED BIOLOGICAL AND PALEONTOLOGICAL APPROACH Timothy Ian Astrop Dissertation Approved: Accepted: _______________________________ _______________________________ Advisor Department Chair Dr. Stephen C. Weeks Dr. Monte E. Turner _______________________________ _______________________________ Committee Member Dean of the College Dr. Lisa E. Park Dr. Chand Midha _______________________________ _______________________________ Committee Member Dean of the Graduate School Dr. Franscisco R. Moore Dr. George R. Newkome _______________________________ _______________________________ Committee Member Date Dr. Joel Duff _______________________________ Committee Member Dr. Peter Niewerowski ii ABSTRACT This doctoral dissertation reports the results of a multi-faceted investigation into the evolutionary dynamics of sexual systems over geologic time using the fossil record of the bivalved branchiopod crustacea in the Order Spinicaudata. The difficulty of assessing the sex of fossils (and by extension, the sexual system employed in extinct organisms) is widespread, and in those taxa that do show sexual dimorphism (e.g., ammonites, some arthropods, and vertebrates), reproductive mechanisms are often invariant, making assessments of reproductive evolution impossible. In this study, new techniques have been developed that will allow the identification of sexes in fossil crustaceans within the taxon Spinicaudata (“clam shrimp”): an enigmatic group of crustaceans with a unique bivalved carapace. Clam shrimp are well-represented in the fossil record, and have a broad array of reproductive types: dioecy (males + females), androdioecy (males + hermaphrodites) parthenogenesis (asexual females), and selfing hermaphroditism. These projects combine the wealth of information about the evolutionary transitions among these various reproductive types gleaned from studies of extant clam shrimp, with the rich representation of clam shrimp throughout the fossil record (from the Devonian to the modern day) to address two canonical hypotheses of reproductive evolutionary theory: (1) that unisexual species should be short lived and less speciose than their outcrossing counterparts and (2) that androdioecy is an unstable, transitionary system that should not persist over long periods of time. These studies iii provide much needed reviews of existing paleontological and biological research regarding the Spinicaudata, assess their taphonomic fidelity using a number of experimental techniques, develops and tests a morphometric protocol for identifying sexes in fossil populations and subsequently extends these shape comparisons using a large collection of fossil clam shrimp taxa from across the world to characterize sex- specific shape differences among various fossil clam shrimp lineages. We then combine these methods to assess sex ratios in fossil clam shrimp, which are indicative of mating system type in modern taxa, thereby allowing us to assign mating system to fossil species. These combined techniques allow, for the first time, investigation of the two evolutionary questions in the studies noted above and to test theories of breeding system evolution that, to date, have remained elusive to empirical assessment and provide a foundation for future research utilizing the fossil record to perform transformative studies into the evolution of mating systems. iv DEDICATION This dissertation represents the culmination of five years of research which I could not have done without the support of my loving wife, Rebecca and my Family; Sue, Ian, Josh, Rose, Alan, Margaret, Roy, Elizabeth, Andrew, Charlotte, James and Cyril. Thank you all for believing in me and being there when we were so far away. v ACKNOWLEDGEMENTS Firstly and most importantly I would like to thank Dr Stephen Weeks for being an excellent mentor and advisor, Dr Lisa Park for her help and support regarding all things palaeontological and Dr Paco Moore for sharing his enthusiasm for the study of evolution with me. I would also like to acknowledge the following researchers who enthusiastically helped me with many aspects of this study, provided helpful feedback and advice, selflessly offered up their time to help me and regularly proved to me that collaborative science is often the most rewarding: Dr Thomas Hegna (University of Western Illinois) for his continuing collaboration and enthusiasm for all things arthropodan. The APSOMA listserve for being an excellent community and always getting me the hard to find texts. Bryan Brown for being an excellent and dedicated student. The Integrated bioscience students, particularly Lara Roketenetz, Rafael Maia, Alyssa Stark and Dr Heath Garris. Yahui Li & Justin Brantner (UAKRON) for assistance in obtaining thick sections, Thomas Quicke (UAKRON) Dr Roman Rakitov and Dr Alexey Kotov (PIN, Russia) for SEM assistance, Olga Ryzhkova (PIN Russia) for helping to translate some of Novojilov's older texts which were extremely helpful and my very good friends Dr Oscar Gallego, Dr vi Mateo Monferran (CONNICET, Argentina) and Drs Li Gang, Shen Yan-Bin & Chen Pei-Ji (NIGPAS, China) for access to their excellent collections and wonderful hospitality. I would also like to thank Reena & Jody Goodwin, Dr Kathryn Metz and Priscilla Callos for their support, encouragement and friendship. vii TABLE OF CONTENTS Page LIST OF TABLES .................................................................................................................... xi LIST OF FIGURES ................................................................................................................ xiii CHAPTER I. THE NATURAL HISTORY OF INVERTEBRATE SEXUAL SYSTEMS ............................. 1 Introduction ................................................................................................... 1 Bdelloid Rotifers ............................................................................................. 6 Darwinulid Ostracods ..................................................................................... 9 Orabatid Mites ............................................................................................. 10 Timema Stick Insects .................................................................................... 12 Caenorhabditis Nematode Worms .............................................................. 16 Aphids .......................................................................................................... 17 Scale Insects ................................................................................................. 18 Hypobiosis .................................................................................................... 21 The Order Spinicaudata ............................................................................... 23 II. DECIPHERING THE STRUCTURE AND TAXONOMIC SIGNIFICANCE OF THE ‘CONCHOSTRACAN’ CARAPACE (BRANCHIOPODA: SPINICAUDATA, LAEVICAUDATA, CYCLESTHERIIDA) ............................................................................................................................. 31 Overview ...................................................................................................... 31 viii Introduction ................................................................................................. 32 The Arthropod Cuticle .................................................................................. 34 The Conchostracan Carapace ...................................................................... 36 The Carapace in Systematics........................................................................ 40 Methods ....................................................................................................... 45 Taphonomy .................................................................................................. 47 Results and Discussion ................................................................................. 49 Conclusions .................................................................................................. 66 III. QUANTIFYING THE COMPOSITIONAL & MATERIAL PROPERTIES OF THE SPINICAUDATAN CARAPACE – INTEGRATING MATERIAL SCIENCE AND EXPERIMANTAL TAPHONOMY ............................................................................................................................. 73 Overview ...................................................................................................... 73 Introduction ................................................................................................. 74 Methods ....................................................................................................... 80 Statistical Analysis ........................................................................................ 90 Results .......................................................................................................... 90 Materials Testing ......................................................................................... 93 Discussion..................................................................................................... 98 Conclusions ...............................................................................................
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