THE ECOLOGY AND PALEOBIOGEOGRAPHY OF FRESHWATER MUSSELS (FAMILY:UNIONIDAE) FROM SELECTED RIVER BASINS IN TEXAS Charles R. Randklev, B.S. Dissertation Prepared for the Degree of DOCTOR OF PHILOSOPHY UNIVERSITY OF NORTH TEXAS May 2011 APPROVED: James H. Kennedy, Major Professor Miguel F. Acevedo, Committee Member David K. Britton, Committee Member Thomas W. La Point, Committee Member Steve Wolverton, Committee Member Art Goven, Chair of the Department of Biological Sciences James D. Meernik, Acting Dean of the Toulouse Graduate School Randklev, Charles R. The Ecology and Paleobiogeography of Freshwater Mussels (Family: Unionidae) from Selected River Basins in Texas. Doctor of Philosophy (Biology), May 2011, 109 pp., 12 tables, 19 figures, references, 188 titles. This dissertation has two overall objectives: first, to demonstrate the utility of paleozoological data for ongoing and future mussel-conservation efforts in Texas and second, to evaluate whether simple measures of habitat (e.g., water depth, velocity and particle size) are important for demonstrating the within-habitat spatial separation of mussels. Although these topics may seem disparate, both are important for increasing our understanding of unionid ecology and biogeography. Chapters 1 through 3 examine the use of paleozoological data for mussel conservation. Although these types of data are not new they have rarely been used in mussel conservation efforts within Texas. This is unfortunate because paleozoological data can provide an excellent record of the mussel fauna prior to wide-scale modern impacts and in areas where historical survey data are lacking. Chapter 4 examines whether assessments of microhabitat for mussels using simple measures of habitat (e.g., water velocity, depth and particle size) are useful. Recent studies have suggested that these measures do not explain the mussel distribution in flowing streams. If this is correct, instream flow studies using this approach need to be revised. Results of Chapter 4 indicate that mussels in the lower Brazos River basin are constrained in distribution by the availability of heterogenous substrate. Appendix A, details the first account of a living population of Truncilla macrodon, which is a candidate species for the Endangered Species Act (ESA). The population was found while conducting mussel instream flow studies in the lower Brazos River basin. Copyright 2011 by Charles R. Randklev ii ACKNOWLEDGMENTS I would like to thank the following people: My major professor Dr. James H. Kennedy for all of his assistance, patience and providing an outlet for my passion regarding the conservation of freshwater mussels. Dr. Steve Wolverton helped me to understand the value of paleozoological data and conveyed the importance of clear and concise writing. Drs. Miguel F. Acevedo and Thomas W. La Point whose courses in statistics and experimental design have greatly improved how problems examined in the following chapters were tested and analyzed and Dr. David Britton for his friendship and guidance over the years. Finally, I would especially like to thank Ben Lundeen and Joe Skorupski for their help and companionship in the field. Portions of this dissertation would not have been possible without their help. I would finally like to thank my wife, Jennifer Randklev, who has been my biggest supporter in all my endeavors. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS.....................................................................................................................iii LIST OF TABLES.................................................................................................................................... vi LIST OF FIGURES ................................................................................................................................viii Chapters 1. LATE HOLOCENE BIOGEOGRAPHY OF UNIONIDS IN NORTH TEXAS ....................... 1 Introduction................................................................................................................................................. 1 Study Area............................................................................................................................................ 5 Materials and Methods .............................................................................................................................. 7 Results ......................................................................................................................................................... 9 Discussion ................................................................................................................................................. 13 Conclusion ................................................................................................................................................ 18 2. CONSERVATION IMPLICATIONS OF THE LATE HOLOCENE UNIONID FAUNA ... 19 Introduction............................................................................................................................................... 19 Background ........................................................................................................................................ 21 Materials and Methods ............................................................................................................................ 24 Results ....................................................................................................................................................... 26 Discussion ................................................................................................................................................. 32 Conservation Status........................................................................................................................... 34 Potential Reasons for Decline.......................................................................................................... 36 Management Implications ................................................................................................................ 39 3. A BIOMETRIC TECHNIQUE FOR ASSESSING PREHISTORIC FRESHWATER MUSSEL POPULATION DYNAMICS (FAMILY: UNIONIDAE) IN NORTH TEXAS.... 41 Introduction............................................................................................................................................... 41 Materials and Methods ............................................................................................................................ 46 Results ....................................................................................................................................................... 51 Modern Case Study: Lake Nocona ................................................................................................. 52 Prehistoric Case Study...................................................................................................................... 54 Discussion ................................................................................................................................................. 56 Conclusion ................................................................................................................................................ 58 iv 4. HABITAT UTILIZATION OF FRESHWATER MUSSELS (FAMILY: UNIONIDAE) IN THE LOWER BRAZOS RIVER BASIN ...................................................................................... 60 Introduction............................................................................................................................................... 60 Materials and Methods ............................................................................................................................ 63 Study Area.......................................................................................................................................... 63 Sampling Methods............................................................................................................................. 63 Data Analysis ..................................................................................................................................... 65 Results ....................................................................................................................................................... 67 Discussion ................................................................................................................................................. 71 5. SUMMARY AND CONCLUSIONS ............................................................................................. 76 APPENDIX: FIRST ACCOUNT OF A LIVING POPULATION OF Truncilla macrodon................................................................................................................................................... 81 LITERATURE CITED ........................................................................................................................... 87 v LIST OF TABLES TABLE 1. List of “lowland” species (Neck 1990) thought to distinguish upper from lower unionid faunas in the Trinity River. ................................................................................................ 4 TABLE 2. Dates of impoundment for watercourses near archaeological sites in the upper Trinity River drainage. ................................................................................................................................ 6 TABLE 3.