The Distribution and Abundance of Macro-Invertebrates in the Major Vegetation Communities of Marion Island and the Impact of Alien Species
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The distribution and abundance of macro-invertebrates in the major vegetation communities of Marion Island and the impact of alien species by Christine Hanel Submitted in partial fulfilment of the requirements for the degree Master of Science, in the Faculty of Biological and Agricultural Sciences (Department of Zoology and Entomology) University ofPretoria August 1999 CONTENTS PAGE Table of contents . 1 Acknowledgements . 5 Abstract ..................................................................................................... 7 CHAPTER 1. INTRODUCTION 1.1 Background, rationale and objectives ..................................... 9 1.2 Locality and environment of Marion Island 1.2.1 Location and topography............................................ 13 1.2.2 Geological and human history .. .. .. .. .. .. .. .. .. .. .. .. .. .... ..... .. 13 1.2.3 Climate . 14 1.2.4 Vegetation ............................................................. 16 1.2.5 Fauna .................................................................... 22 1.2.5.1 Vertebrates ................................................... 22 1. 2. 5. 2 Terrestrial invertebrates . 22 1.3 References . .. 27 CHAPTER 2. TERRESTRIAL MACRO INVERTEBRATE DENSITY AND BIOMASS IN LOWLAND VEGETATION COMMUNITIES 2.1 Introduction ................................................................... 33 2.2 Methods 2.2.1 1996 I 97 ................................................................ 36 2.2.1.1 Study site .............................................................. 36 2.2.1.2. Sampling materials and methods .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 36 2.2.1.3 Analysis ................................................................ 37 1 2.2.2 1976 I 77 ............................................................... 38 2.2.2.1 Study site . 39 2.2.2.2 Sampling materials and methods . 39 2.2.2.3 Analysis . .. 39 2.3 ltesults 2.3.1 1996 I 97 .............................................................. 40 2.3.1.1 Densities and biomass ..................................... 40 2.3.1.2 Seasonality .................................................... 45 2.3.1.3 Habitat specificity ........................................... 47 2.3 .2 1976177 Densities and biomass . 50 2.3.3 Comparisons 1976177 versus 1996197 .............................. 55 2.4 Discussion 2.4.1 Seasonality of invertebrates . ...... .. 59 2.4.2 Habitat specificity . 60 2.4.3 Comparisons between species abundances in 1976177 and 1996197 ............................................. 62 2.5 lteferences . 65 CHAPTER 3. THE IMPACT OF A SMALL, ALIEN INVERTEBRATE LIMNOPHYES MIN/MUS (DIPTERA, CHIRONOMIDAE) 3.1 Introduction . .. 70 3.2 Materials and methods 3.2.1 Species biology .............................................................. 71 3 .2.2 Sampling procedure and data analysis ............................. 71 3.3 ltesults . 73 3.4 Discussion . 79 3.5 lteferences . .. 82 2 CHAPTER 4. RECORDS OF ALIEN INSECT SPECIES 4.1 Vanessa cardui and newly established alien species . 86 4.2 References ..................................................................... 90 CHAPTER 5. CONCLUSIONS . 92 5.1 References . 94 Appendix I Fifty years at Marion and Prince Edward Islands: a bibliography of scientific and popular literature .......................... 95 3 ''A scientist is someone with the time and inclination to wonder'' James Lovelock .... I wander .... Christine Hanel Dedicated to: Marion and all the sub-Antarctic Islands 4 Acknowledgements The Marion Island Terrestrial Invertebrate Ecology (M.I.T.I.E.) program was initiated by Prof Steven Chown, Department of Zoology and Entomology, University of Pretoria, who has directed it throughout. If coincidence is not another word for global ecosystem functioning, then how else could I explain the opportunity that came my way via the Namib Desert while on the opposite side of the continent from the M.I.T.I.E. administration desk, from where in turn the message came that led me back to Marion - for no other reason but - another facet of ecosystem functioning. That in a nutshell only sketches an outline of the coincidences for which I am grateful. They are however linked by a far more intricate network that could if described in more detail parallel the writing of another thesis in place of the acknowledgements here. Thus I will stick to the core, which centres around the opportunity given to me to work on Marion Island. For this chance, and all the others that went along with and arose from it, including the acceptance of the field work as a basis for the formal form of furthering my education, I have Steven Chown's motivation, dedication (to Marion and the other sub-Antarctic Islands), and faith (if not that, then whatever it took not to show his frustration) against all my odds (e.g., logistical but most of all mental) to thank. Also for appreciating that my strength lies in the field, rather than in theory. My thanks also go to those that contributed most directly towards the assimilation of comparative data, without which the synthesis and significance of my work alone would not have been possible. Thus I thank all the other 11 members of the Marion 53 (1996/97) overwintering team for their interest and dedicated participation in collecting and reporting on any alien invertebrates seen during the year, which led to the discovery of species not recorded before, and a reference collection that would not have been possible without their various ingenious, humorous, and always well-meaning 'not to hurt a fly' methods of pursuing 'goggas' (e.g., using converted vegetable sacks as insect nets, performing endurance runs after flutter-by's, bird feathers, and illusive bottles of red wine). I am also grateful to Dr. Niek Gremmen for his advice and active field part in choosing the representative vegetation types and his assistance in showing or answering my lay questions on plants and their identification. To Dr. Alan Burger, Department of Biology, University of Victoria, Canada, my sincere thanks and respect for having kept and entrusted sending me the "scientific data with no commercial value" that contains the most sought after and indeed invaluable information on his invertebrate work done 20 years prior to mine. Without this data, no meaningful comparison could have been made to document the plight ofMarion's indigenous invertebrates in scientific form. In connection with the study of L. minimus, I thank Dr. Y. Delettre (Universite de Rennes 1) for his interest and advice. For help in the identification of the alien species, I thank Drs. M.W. 5 Mansell and M. Stiller (Plant Protection Research Institute, Pretoria) for the identification of the Diptera (Anthomyiidae and Lonchaeidae) and Hemiptera, respectively, Drs. M. Kruger and the late S. Endrody-Younga (Transvaal Museum, Pretoria) for identification of the Lepidoptera and Coleoptera, respectively, and Dr. H. Robertson (South African Museum, Cape Town) for identification of the ant. I am also grateful to Steven Chown for his supervision and support throughout the project, which often stretched not only from different corners of the earth, but to involvement in the inadvertent effects of the new South African obstacles to the progress of my work. I appreciate in particular all his verbal, manual, and electronic input to the manuscript. Much appreciated were also the comments of Dr. M.A. McGeoch (University of Pretoria) on earlier drafts of some chapters. Financial and logistic support for the scientific research at Marion Island was provided by the South African Department of Environmental Affairs & Tourism (SA-DEA&T), on the advice of the South African Committee on Antarctic Research. Home-based facilities were provided by the University of Pretoria, and the South African Foundation for Research Development provided MSc funding towards the final writing up phase. My appreciation for this support lies in knowing what it takes to fund oneself without it. 6 ABSTRACT In this study macro-invertebrates were sampled quantitatively in 10 lowland vegetation communities on Marion Island over a one-year period commencing in May 1996 as part of a larger investigation into the distribution, abundance and species energy use of invertebrates across an altitudinal transect on Marion Island. The data collected for this particular study were used to investigate the. habitat specificity and seasonality of the macro-invertebrates, as well as the impact of alien species on the local community. As part of the latter study a watching brief for alien species was kept throughout the field year and the alien species list was updated accordingly. The quantitative data were also used to compare changes in the density and biomass of selected macro-invertebrate species between 1976/77 and 1996/97 by reworking the data on macro-invertebrates collected by Alan Burger in 1976/77 during the course of his work on the Lesser Sheathbill. In the current study it was found that the majority of the macro-invertebrate species are not particularly habitat specific. Rather, they generally prefer either moist mire habitats, or the more well-drained non-mire vegetation complexes. In addition, many of the species had pronounced peaks in abundance in a given season (winter, summer, autumn and spring peaks were recorded), although this seasonality varied between species and between habitats for a given species. Although this finding does not support previous generalizations concerning an absence of seasonality in sub-Antarctic invertebrates, it does show that