Distribution and Structure of Arthropod Communities in Relation to Resource Patches and Spatial Scale in Dryland Woodland Ecosystems
Total Page：16
File Type：pdf, Size：1020Kb
Distribution and structure of arthropod communities in relation to resource patches and spatial scale in dryland woodland ecosystems Alan B. C. Kwok Evolution and Ecology Research Centre School of Biological, Earth and Environmental Sciences University of New South Wales Sydney, NSW, 2052 Australia PhD thesis March 2012 THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Kwok First name: Alan Other name/s: Bing Choong Abbreviation for degree as given in the University calendar: PhD School: Biological, Earth and Environmental Faculty: Science Sciences Title: Distribution and structure of arthropod communities in relation to resource patches and spatial scale in dryland woodland ecosystems Abstract 350 words maximum: (PLEASE TYPE) In dryland ecosystems, resources such as water, nutrients and habitat are concentrated into discrete patches. This resource concentration occurs at fine (e.g. around trees, grasses or logs) and broad (e.g. habitat remnants within an agricultural matrix) scales. Arthropods, which include insects, spiders, and a range of other invertebrates, provide a range of critical ecosystem functions in drylands. Arthropods may be particularly sensitive to changes in resource concentration given their small size and habitat requirements. Limited research, however, has examined how arthropods respond to changes in resource concentration across different spatial scales. This thesis examines how the concentration of resources affects the distribution and structure of arthropod communities at multiple spatial scales in south-eastern Australia. Chapter 1 provides an overview of resource patchiness in arid and semi-arid ecosystems, and describes how it is known to affect the biota. Chapters 2 to 4 investigate how the fine-scale distribution of resources (plants, and plant-associated patches) affects the distribution and composition of arthropod communities at local (plant-plant) scales. Specifically, chapter 2 examines how plant species and density affect the plant-resident arthropod fauna in a semi-encroached shrubland, and demonstrates that plant species is the overwhelming driver of arthropod diversity in these communities. Chapters 3 and 4 examine how the multilayered resource patch created by a dominant tree (mallee, Eucalyptus spp.) structures arthropod communities in mallee woodlands. At fine-scales, the canopy patch beneath mallee trees supports a distinct suite of arthropods compared to inter-tree areas. This is influenced by fire, which has taxon-specific effects. Chapters 5 and 6 investigate how the concentration and health of remnant patches at landscape scales affects arthropods. Chapter 5 evaluates the use of common landscape health indices as indicators of arthropod (spider, ant, and beetle) biodiversity, illustrating that these indices show only weak or inconsistent relationships with arthropod biodiversity. Chapter 6 uses a multi-scale approach to investigate the drivers of ant community structure in a fragmented grassy–box woodland. It indicates that finer-scale characteristics (particularly tree canopy cover and soil texture) drive ant communities within these landscapes. Chapter 7 summarises the findings and implications of the thesis, and proposes avenues for future research. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). ………………………………………………………… ……………………………………..…………… ……….…………………… … … ...…….… Signature Witness Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: THIS SHEET IS TO BE GLUED TO THE INSIDE FRONT COVER OF THE THESIS Originality Statement ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed..................... Date......................... Copyright Statement ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed ……………………………………………........................... Date ……………………………………………........................... Authenticity Statement ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed ……………………………………………........................... Date ……………………………………………........................... "If we and the rest of the backboned animals were to disappear overnight, the rest of the world would get on pretty well. But if invertebrates were to disappear, the land's ecosystems would collapse. The soil would lose its fertility. Many of the plants would no longer be pollinated. Lots of animals - amphibians, reptiles, birds, mammals - would have nothing to eat. These small creatures are within a few inches of our feet wherever we go on land, but often they are disregarded. We would do very well to remember them." ~ Sir David Attenborough ~ PREFACE This dissertation consists of five stand-alone manuscripts (Chapters 2 to 6) that have been published, recently submitted for publication, or are intended for publication in peer-reviewed journals. Each chapter is self-contained and subsequently, there will be some repetition. A single reference list has been provided at the end of the dissertation to avoid unnecessary duplication. This thesis is a compilation of my own work, with guidance from my supervisor David Eldridge. All chapters were conceptualised either by myself or jointly with David Eldridge. I conducted all data analyses and wrote and illustrated the manuscripts. Specific details for each chapter and the contribution of co-authors are detailed below. Chapter 2: A. B. C Kwok and D. J. Eldridge. Shrub species, not spatial arrangement, structures arthropod communities in a shrub-encroached woodland Study was conceptualised by Alan Kwok. David Eldridge provided guidance on the study design and structure of the manuscript in his role as academic supervisor. Submitted for publication in Insect Conservation and Diversity. Chapter 3: A. B. C Kwok and D. J. Eldridge. Do trees modulate ground-dwelling arthropod communities in the mallee of south-eastern Australia? Study was conceptualised by Alan Kwok. David Eldridge provided guidance on study design and the structure of the manuscript in his role as academic supervisor. i Chapter 4: A. B. C Kwok and D. J. Eldridge. Does fire affect the ground- dwelling arthropod community through changes to fine-scale resource patches? Study was conceptualised by Alan Kwok. David Eldridge provided guidance on the study design and structure of the manuscript in his role as academic supervisor. Chapter 5: A. B. C Kwok, D. J. Eldridge and I. Oliver. Do landscape health indices reflect arthropod biodiversity status in the eucalypt woodlands of eastern Australia? Austral Ecology, 36, 800 - 813. Manuscript was conceptualised by Alan Kwok. David Eldridge assisted with parts of the statistical analyses and Ian Oliver established the project upon which the data were derived and contributed intellectually to the development of the manuscript. Chapter 6: A. B. C Kwok, D. J. Eldridge and D. Freudenberger.