Documenting the association between a non-geniculate coralline red alga and its molluscan host Rosemary Eager Department of Biodiversity & Conservation Biology University of the Western Cape P. Bag X17, Bellville 7535 South Africa A thesis submitted in fulfillment of the requirements for the degree of MSc in the Department of Biodiversity and Conservation Biology, University of the Western Cape. Supervisor: Gavin W. Maneveldt March 2010 I declare that “Documenting the association between a non-geniculate coralline red alga and its molluscan host” is my own work, that it has not been submi tted for any degree or examination at any other university, and that all the sources I have used or quoted have been indicated and acknowledged by complete references. 3 March 2010 ii I would like to dedicate this thesis to my husband, John Eager and my children Gabrian and Savannah for their patience and support. Last, but never least, I would like to thank GOD for sustaining me during this project. iii TABLE OF CONTENTS Abstract .........................................................................................................................................1 Chapter 1: Literature Review 1.1 Zonation on rocky shores....................................................................................................5 1.1.1 Factors causing zonation ...........................................................................................6 1.2 Plant-animal interactions on rocky shores .........................................................................7 1.2.1 Trophic interactions...................................................................................................7 1.2.2 Non-trophic interactions............................................................................................8 1.3 Ecology of winkles .............................................................................................................9 1.4 Ecology of encrusting coralline algae ..............................................................................11 1.4.1 Mollusc-coralline interactions.................................................................................16 1.4.2 Winkle-coralline associations .................................................................................18 Chapter 2: Aim of Study 2.1 South African west and south coast rocky shore zonation patterns ................................19 2.2 Observation .......................................................................................................................19 2.3 Aim of Study.....................................................................................................................20 Chapter 3: Ecology of Oxystele in South Africa 3.1 Introduction.......................................................................................................................23 3.2 General ecology and distribution......................................................................................23 3.3 Factors influencing the vertical distribution of Oxystele species ....................................27 3.3.1 Physical factors........................................................................................................27 3.3.2 Biological factors.....................................................................................................29 3.4 Reproductive Biology of Oxystele species.......................................................................30 Chapter 4: General ecology of O. sinensis 4.1 Introduction.......................................................................................................................32 4.2 Materials and methods......................................................................................................34 4.2.1 Study site..................................................................................................................34 4.2.2 Natural invertebrate densities and biomass ............................................................35 4.2.3 Frequency of the winkle-coralline association .......................................................36 4.2.4 Mean coralline load .................................................................................................36 4.2.5 Statistical analysis....................................................................................................37 4.3 Results ...............................................................................................................................37 4.3.1 Natural invertebrate community structure ..............................................................37 4.3.2 Frequency and potential burden of the association ................................................40 4.4 Discussion .........................................................................................................................42 Chapter 5: Identification of the coralline alga 5.1 Introduction.......................................................................................................................45 5.2 Materials and methods......................................................................................................47 5.2.1 Taxonomy ................................................................................................................47 5.2.2 Frequency of gametangial and sporangial material ................................................49 5.2.3 Statistical analysis....................................................................................................49 iv 5.3 Observations......................................................................................................................50 5.4 Results ....................................................................................................................... ........60 5.4.1 Taxonomy ................................................................................................................60 5.4.2 Frequency of gametangial and sporangial material ................................................61 5.5 Discussion .........................................................................................................................63 Chapter 6: Algal cover abundance and competitive interactions 6.1 Introduction.......................................................................................................................67 6.2 Materials and methods......................................................................................................69 6.2.1 Natural algal percent cover abundance ...................................................................69 6.2.2 Interference competitive interactions......................................................................69 6.2.3 Diversity...................................................................................................................70 6.2.4 Statistical analysis....................................................................................................71 6.3 Results ...............................................................................................................................71 6.3.1 Natural algal percent cover abundance ...................................................................71 6.3.2 Interference competitive interactions......................................................................74 6.3.3 Diversity...................................................................................................................75 6.4 Discussion .........................................................................................................................76 Chapter 7: Coralline attachment strength and percentage burrowing 7.1 Introduction.......................................................................................................................79 7.2 Materials and methods......................................................................................................81 7.2.1 Attachment strength and percent burrowing...........................................................81 7.2.2 Primary and secondary thallus thickness ................................................................81 7.2.3 Statistical analysis....................................................................................................82 7.3 Results ...............................................................................................................................82 7.4 Discussion .........................................................................................................................83 Chapter 8: Host dependency 8.1 Introduction.......................................................................................................................87 8.2 Materials and methods......................................................................................................87 8.2.1 Statistical analysis....................................................................................................90 8.3 Results ...............................................................................................................................90 8.4 Discussion .........................................................................................................................92 Chapter 9: Substrate preference of the coralline alga 9.1 Introduction.......................................................................................................................93