Plant-frugivore interactions in a heterogeneous forest landscape of South Africa Dissertation In partial fulfilment of the requirements for the award of a Doctorate Degree in Natural Sciences (Dr. rer. nat) The Faculty of Biology, Philipps-University of Marburg Lackson Chama, MSc Sinazongwe (Zambia) June 2012, Marburg From the Faculty of Biology, Philipps-University Marburg als Dissertation am angenommen. Dekan: Prof. Dr. Paul Galland Erstgutachterin: Prof. Dr. N. Farwig Zweitgutachter: Prof. Dr. R. Brandl Tag der Disputation: 25th June 2012 Dedicated to my son, Mishila, who’s first two years on earth I was hardly part of, due to my commitment towards this work. Contents CHAPTER 1: GENERAL INTRODUCTION ..................................................................................................................... 3 EFFECTS OF HUMAN ACTIVITIES ON FOREST BIODIVERSITY ........................................................................................................ 4 PLANT-FRUGIVORE INTERACTIONS IN CHANGING LANDSCAPES .................................................................................................. 5 THE ROLE OF FUNCTIONAL DIVERSITY IN FRUGIVORE COMMUNITIES ........................................................................................... 5 EFFECTS OF SEED INGESTION BY FRUGIVOROUS BIRDS ON GERMINATION SUCCESS ........................................................................ 6 AIMS OF THE THESIS .......................................................................................................................................................... 7 REFERENCES .................................................................................................................................................................... 9 CHAPTER 2: PLANT-FRUGIVORE NETWORKS IN MODIFIED LANDSCAPES ................................................................. 13 ABSTRACT ..................................................................................................................................................................... 14 INTRODUCTION .............................................................................................................................................................. 15 MATERIAL AND METHODS ............................................................................................................................................... 17 RESULTS ....................................................................................................................................................................... 20 DISCUSSION .................................................................................................................................................................. 23 CONCLUSION ................................................................................................................................................................. 26 ACKNOWLEDGMENTS ...................................................................................................................................................... 27 REFERENCES .................................................................................................................................................................. 28 CHAPTER 3: FUNCTIONAL DIVERSITY OF FRUGIVORE COMMUNITIES IN MODIFIED LANDSCAPES ........................... 33 ABSTRACT ..................................................................................................................................................................... 34 INTRODUCTION .............................................................................................................................................................. 35 MATERIAL AND METHODS ............................................................................................................................................... 37 RESULTS ....................................................................................................................................................................... 41 DISCUSSION .................................................................................................................................................................. 46 CONCLUSIONS ................................................................................................................................................................ 50 ACKNOWLEDGEMENTS .................................................................................................................................................... 50 REFERENCES .................................................................................................................................................................. 51 CHAPTER 4: THE IMPORTANCE OF FRUGIVORES FOR GERMINATION SUCCESS OF PLANT SPECIES .......................... 57 ABSTRACT ..................................................................................................................................................................... 58 INTRODUCTION .............................................................................................................................................................. 59 MATERIAL AND METHODS ................................................................................................................................................ 60 RESULTS ....................................................................................................................................................................... 63 DISCUSSION .................................................................................................................................................................. 66 CONCLUSIONS ................................................................................................................................................................ 67 ACKNOWLEDGMENTS ...................................................................................................................................................... 67 REFERENCES .................................................................................................................................................................. 69 CHAPTER 5: GENERAL CONCLUSIONS ...................................................................................................................... 72 SUMMARY OF METHODS AND KEY FINDINGS ........................................................................................................................ 73 IMPLICATIONS FOR CONSERVATION .................................................................................................................................... 74 FUTURE RESEARCH PROSPECTS .......................................................................................................................................... 76 DEUTSCHE ZUSAMMENFASSUNG ............................................................................................................................ 77 APPENDICES ............................................................................................................................................................ 80 1 APPENDIX A .................................................................................................................................................................. 81 APPENDIX B …………………………………………………………………………………………………………………………………..……… 83 APPENDIX C ................................................................................................................................................................... 84 APPENDIX D .................................................................................................................................................................. 86 ACKNOWLEDGMENTS ............................................................................................................................................. 87 CURRICULUM VITAE ................................................................................................................................................ 90 ERKLÄRUNG ............................................................................................................................................................ 92 2 Chapter 1: General Introduction 3 Effects of human activities on forest biodiversity Human-driven activities constitute the most serious threat linked with the loss of Earth's biological diversity (Forman & Collinge 1996, Bergman et al. 2004, Gibson et al. 2011). A recent global assessment of the impacts of human disturbance on biodiversity by Gibson et al. (2011) suggests that these threats are particularly high in tropical forest landscapes where both species diversity and human pressures on natural environments are high. The rapid increase in human land-use activities involving the conversion of tropical forests for agriculture and timber production (FAO 2006, Gibson et al. 2011) has not only considerably reduced the sizes of remaining forest, but also disproportionally increased the size of human dominated matrix surrounding these forest patches (Debinski & Holt 2000, Fahrig 2003). This leads to increased forest isolation and can undermine the quality of forest habitats (Saunders et al. 1991, Wunderle 1997, Fischer & Lindenmayer 2007). Moreover, these changes can alter the physical space where species grow and interact, and thus trigger biological responses that