Vom Fachbereich Biologie der Universität Kaiserslautern zur Verleihung des akademischen Grades „Doktor der Naturwissenschaften“ genehmigte Dissertation Long-term changes of vascular epiphyte assemblages in the tropical lowlands of Panama by STEFAN LAUBE D 386 Kaiserslautern 2006 Tag der wissenschaftlichen Aussprache: 25. Juli 2006 Vorsitzender der Prüfungskommission: Prof. Dr. Joachim W. Deitmer 1. Gutachter: Prof. Dr. Burkhard Büdel 2. Gutachter: PD Dr. Gerhard Zotz List of papers This thesis is based on the following papers: Paper I: Laube, S. and G. Zotz (2006) “Long-term changes of the vascular epiphyte assemblage on the palm Socratea exorrhiza in a lowland forest in Panama.” Journal of Vegetation Science 17: 307-314 Paper II: Laube, S. and G. Zotz (2006) “Neither host specific nor random: vascular epiphytes on three tree species in a Panamanian rainforest.” Annals of Botany 97: 1103-1114 Paper III: Laube, S. and G. Zotz, “A metapopulation approach to the analysis of long- term changes in the epiphyte vegetation of Annona glabra .” (manuscript) My contribution to the papers Paper I: We used data collected for another research project (Zotz and Vollrath, 2003). I collected the data of the 2004 epiphyte census. Further I conducted all analyses and wrote the text. Zotz provided helpful comments and discussion on the text. Paper II: I am responsible for the idea, conducting most of the analyses and writing the text. Zotz provided the data from an earlier work (Zotz and Vollrath, 2003), performed the Canonical Correspondence Analysis, and made helpful comments on the text. Paper III: This study builds on a previous study by Zotz et al. (1999). Zotz suggested the study and provided helpful comments on the text. I conducted the data sampling. Further, I suggested the analysis approach, conducted the analyses and wrote the text. Contents ABSTRACT .................................................................................................................................. XI LIST OF FIGURES......................................................................................................................XII LIST OF TABLES ..................................................................................................................... XIV LIST OF ABBREVIATIONS ......................................................................................................XV CHAPTER 1 - INTRODUCTION .................................................................................................. 1 DYNAMICS IN PLANT COMMUNITIES ............................................................................................. 1 CURRENT KNOWLEDGE ................................................................................................................. 2 AIMS ............................................................................................................................................. 5 CHAPTER 2 – GENERAL METHODS AND STUDY SITES ..................................................... 6 SAN LORENZO CRANE SITE ........................................................................................................... 6 Study species ........................................................................................................................... 6 BARRO COLORADO ISLAND .......................................................................................................... 7 Study species ........................................................................................................................... 8 Epiphyte Census ...................................................................................................................... 9 CHAPTER 3 - LONG-TERM CHANGES OF THE VASCULAR EPIPHYTE ASSEMBLAGE ON THE PALM SOCRATEA EXORRHIZA IN A LOWLAND FOREST IN PANAMA...................................................................................................................................... 11 INTRODUCTION ........................................................................................................................... 11 MATERIAL AND METHODS .......................................................................................................... 13 Study site and species............................................................................................................ 13 Data analysis.......................................................................................................................... 14 RESULTS ..................................................................................................................................... 15 Host trees ............................................................................................................................... 15 Epiphyte vegetation ............................................................................................................... 15 DISCUSSION ................................................................................................................................ 22 CHAPTER 4 - NEITHER HOST SPECIFIC NOR RANDOM: VASCULAR EPIPHYTES ON THREE TREE SPECIES IN A PANAMANIAN RAINFOREST......................................... 25 INTRODUCTION ........................................................................................................................... 25 MATERIAL AND METHODS .......................................................................................................... 27 Study site and species............................................................................................................ 27 Data analysis.......................................................................................................................... 27 RESULTS ..................................................................................................................................... 29 Socratea exorrhiza ................................................................................................................. 29 Marila laxiflora ..................................................................................................................... 31 Perebea xanthochyma ............................................................................................................ 32 Spatial patchiness .................................................................................................................. 32 Ordination.............................................................................................................................. 33 DISCUSSION ................................................................................................................................ 36 IX CHAPTER 5 - A METAPOPULATION APPROACH TO THE ANALYSIS OF LONG- TERM CHANGES IN THE EPIPHYTE VEGETATION OF ANNONA GLABRA .....................39 INTRODUCTION ...........................................................................................................................39 MATERIAL AND METHODS ..........................................................................................................41 Study area and epiphyte census .............................................................................................41 Data analysis ..........................................................................................................................42 RESULTS .....................................................................................................................................45 Epiphyte vegetation................................................................................................................45 Species composition...............................................................................................................45 Population change..................................................................................................................45 Species-area relationship, distribution-abundance relationship, regional patch frequency distribution .............................................................................................................................47 Subset of 725 Annona glabra trees........................................................................................50 DISCUSSION ................................................................................................................................58 CHAPTER 6 - CONCLUSION .....................................................................................................62 ACKNOWLEDGEMENTS...........................................................................................................64 REFERENCES...............................................................................................................................66 APPENDICES ...............................................................................................................................77 X Abstract The study provides insights into the dynamic processes of vascular epiphyte vegetation in two host tree species of lowland forest in Panama. Further, a novel approach is presented to examine the possible role of host tree identity in the structuring of vascular epiphyte communities: For three locally common host tree species (Socratea exorrhiza, Marila laxiflora, Perebea xanthochyma ) we created null models of the expected epiphyte assemblages assuming that epiphyte colonization reflected random distribution of epiphytes in the forest. In all three tree