University of Cape Town

253 Pages·2016·2.83 MB·English

Genetics and ecosystem effects of the invasive mussel Semimytilus
algosus, on the West Coast of South Africa

Susanna Catharina Franzina Zeeman
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Supervisors: Emeritus Professor George M. Branch, Dr Deena Pillay
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and Dr Sophie Von der Heyden
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Thesis presented for the Degree of
Doctor of Philosophy
In the Department of Biological Sciences
Faculty of Science
University of Cape Town
February 2016
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The copyright of this thesis vests in the author. No
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quotation from it or information derived from it is to be

published without full acknowledgeement of the source.
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The thesis is to be used for private study or non-
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commercial research purposes only.

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Published by the Universit y of Cape Town (UCT) in terms
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of the non-exclusive license granted to UCT by the author.
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“Unless someone like you cares a whole awful lot,
Nothing is going to get better. It's not.”
Dr. Seuss, The Lorax

This thesis is dedicated to Zirk and Tiaan du Toit without whose support this
work would not have been possible

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Declaration
I, Susanna Catharina Franzina Zeeman, hereby declare that the work on which this thesis is
based is my original work (except where acknowledgements indicate otherwise) and that
neither the whole work nor any part of it has been, is being, or is to be submitted for another
degree in this or any other university. I authorise the University to reproduce for the purpose
of research either the whole or any portion of the contents in any manner whatsoever.
Signature Removed
Susanna Catharina Franzina Zeeman
10 February 2016
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Table of Contents
Acknowledgements.......................................................................................................... 9
Abstract............................................................................................................................ 11
Chapter 1 General introduction, aims and overview ...................................................... 12
Chapter 2 Molecular identification of Semimytilus algosus, Aulacomya atra and an unknown
invasive mussel from Lüderitz in comparisons of southern African and Chilean
populations……………………………………………………………………................ 19
Chapter 3
Field surveys of Semimytilus algosus in South Africa: abundance, zonation and tolerance to
wave exposure…………………………………............................................................... 37
Chapter 4
Comparisons of life-history strategies of S. algosus and three other mussel species on the
West Coast of South Africa ………………………………….......................................... 55
Chapter 5
Field experiments assessing survival, growth, condition, recruitment and interactions between
Semimytilus algosus and Mytilus galloprovincialis at different shore heights.................. 84
Chapter 6
Phylogeography of the invasive mussel Semimytilus algosus in South Africa relative to
natural populations in Chile and Namibia…………………............................................. 126
Chapter 7
Synthesis and conclusions ................................................................................................ 145

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Acknowledgements
This project was made possible through the financial support I received from the NRF
(National Research Foundation), the MBRC (Marine Biology Research Centre), and the
University of Cape Town doctoral research scholarship.
A big ‘thank you’ to my supervisors: George Branch, Deena Pillay and Sophie von der
Heyden. Thank you for your guidance and time.
George: It has been a great privilege to be able to work with you. I enjoyed every minute of
our field trips. Thank you for challenging me and guiding me along the way.
Deena: Your passion for science and the pursuit of knowledge is infectious and inspired me.
Sophie: Entering into the molecular sphere was a big challenge for me during this thesis, I
could not have done it without you. Thank you for your patience in explaining molecular
processes and procedures to an ecologist.
To all those who helped me with fieldwork: Dylan Maeder, Cornelius Brits, Shannon
Hampton, Martin Emanuel, Stuart Norman, Zirk du Toit, Tiaan du Toit, Jess Dawson and
anyone else I have forgotten. Fieldwork is not always ‘fun and games’ and often involves
early mornings out in rain, cold winds or hot sun. Thank you for giving up your time and
energy to assist with the data collection. I could not have done this without your help.
The following people gave technical and logistical support: George Du Plessis, Granville
Faulmann, Petra Muller and Gilly Smith. Thank you for your help and enthusiasm. Deon
Bezuidenhout at Strait Access Technologies (Pty) Ltd allowed me to use their tensometer to
measure byssal strength, and Jandre de Villiers and Jason Voorneveld gave practical advice
on using the machine. The Department of Mechanical Engineering at the University of Cape
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