ResearchOnline@JCU This file is part of the following reference: Wardhaugh, Carl William (2011) Microhabitat utilisation and the spatial distribution of rainforest canopy invertebrate communities. PhD thesis, James Cook University. Access to this file is available from: http://researchonline.jcu.edu.au/32002/ The author has certified to JCU that they have made a reasonable effort to gain permission and acknowledge the owner of any third party copyright material included in this document. If you believe that this is not the case, please contact [email protected] and quote http://researchonline.jcu.edu.au/32002/ Microhabitat Utilisation and the Spatial Distribution of Rainforest Canopy Invertebrate Communities Thesis submitted by Carl William Wardhaugh BSc, MSc, University of Canterbury, NZ In November 2011 For the degree of Doctor of Philosophy In the School of Marine and Tropical Sciences James Cook University, Cairns Statement of Access I, the undersigned, author of this work and copyright owner of this thesis, grant the University a permanent non-exclusive licence to store, display or copy any or all of the thesis, in all forms of media, for use within the University, and to make the thesis freely available online to other persons or organisations. I understand that James Cook University will make this thesis available for use within the University Library and via the Australian Digital Theses network for use elsewhere. I understand that as an unpublished work, a thesis has significant protection under the Copyright Act and I do not wish to place any further restrictions on access to this work. …16/01/2014…… (Signature) (Date) Declaration I declare that this thesis is my own work and has been submitted in any form for another degree or diploma at any university or other institute of tertiary education. Information derived from the published or unpublished work of others has been acknowledged in the text and a list of references is given. ……16/01/2014…… (Signature) (Date) Electronic copy I, the undersigned, the author of this work, declare that the electronic copy of this thesis provided to the James Cook University Library is an accurate copy of the print thesis submitted, within the limits of the technology available. ……16/01/2014…… (Signature) (Date) Declaration on Ethics The research presented and reported in this thesis was conducted within the guidelines for research ethics outlined in the National Statement on Ethics Conduct in Research Involving Humans (1999), the Joint NHMRC/AVCC Statement and guidelines on Research Practice (1997), the James Cook University Policy on Experimentation Ethics, Standard Practices and Guidelines (2001), and the James Cook University Statement and Guidelines on Research Practice (2001). The research methodology did not require clearance from the James Cook University Experimentation Ethics Review Committee. ……16/01/2014…… (Signature) (Date) Statement of the Contribution of Others Nature of Assistance Contribution Name and Affiliation of Co- contributors Intellectual support Data analysis Will Edwards (principal Editorial assistance supervisor), Marine and Tropical Biology, James Cook Univeristy Concept development Nigel Stork (associate Editorial assistance supervisor), Griffith School of Environment, Griffith University Editorial assistance (Chapter Peter Grimbacher, 3 only) Department of Resource Management and Geography, University of Melbourne Financial support APA scholarship MTSRF grant Skyrail Rainforest Foundation student grant Graduate Research Scheme Dedicated to the 40,374 invertebrates who gave their lives for this research… …lest we forget Acknowledgements First and foremost I would like to thank my wife Katherine for all of her support, and for enduring years of subsisting on just her wages and my paltry (but much appreciated) APA scholarship. I would also like to thank my supervisors, Will Edwards and Nigel Stork for all of their help, advice and valuable input. Peter Grimbacher, for all the discussions and collaboration, and for helping to identify those beetles that just didn’t want to be identified. The good people at the Skyrail Rainforest Foundation who provided me with the funds to carry out much of my fieldwork. The Graduate Research School for providing me with the funds to attend the ATBC conference and present my work to the big names in tropical entomology and ecology. This grant also allowed me to travel to Canberra to visit the Australian National Insect Collection to meet many of Australia’s leading entomologists, as well as see one of the largest insect collections in the world. Cassandra Nicols at the canopy crane, for organising all of my fieldtrips, even though the paperwork never seemed to get to her to let her know when I was coming or what I was doing. All of the crane drivers; Andrew Thompson, Shane Kelly, and Russell Holmes. Thanks for not breaking the crane while I was on it, resulting in a perilous descent from the box on a rope. Andrew Krockenberger, Mike Liddell, Sue Kelly, Eva King, Leanne Shilitoe, and Peter Franks for all of their help behind the scenes, crossing the t’s and dotting the i’s. All my friends and family for their support. Sure most of them don’t know exactly what I do, but they support it nonetheless! And anyone else that I have forgotten. Cheers. Go the Drunken Hellfish… Abstract The tropical rainforest is renowned for its high invertebrate species richness. Yet our understanding of the spatial distribution of the invertebrate communities inhabiting tropical rainforest canopies is very poor. Most mass-sampling invertebrate biodiversity studies from the rainforest canopy have either focussed on whole trees, via sampling methods such as canopy fogging, or on subsets of the invertebrate community (usually a particular herbivorous taxonomic group) inhabiting a single microhabitat type (usually the leaves), via hand collection and foliage beating techniques. Consequently, previous studies have been unable to examine the fine-scale spatial distribution of canopy invertebrates within individual trees, or establish where in the canopy different invertebrates are concentrated. This information is vital if we are to make accurate predictions about species and community level responses to disturbance and climate change, or make accurate calculations about ecosystem processes and species richness. I carried out a long-term mass-collecting effort from five canopy microhabitats (mature leaves, new leaves, flowers, fruit, and suspended dead wood) using hand collecting and beating techniques from a canopy crane to examine spatial differences in invertebrate density, diversity, community structure, host specificity, and body size in an Australian tropical rainforest. First, I examined microhabitat differentiation in the invertebrate communities associated with each microhabitat. Specifically, I examined variation between microhabitats in invertebrate density, taxonomic composition and guild structure. I also focused on the beetle community to examine differences between microhabitats in species richness, overlap, abundance patterns, and guild structure. I focused on the beetle community since beetles are arguably the most species-rich taxon on Earth and are biologically diverse. Second, I examined the host specificity of beetles inhabiting different microhabitats to test the assumption that most host specific species are herbivores on the leaves that interact antagonistically with the host tree. This assumption is the basis for many global biodiversity estimates and has resulted in the majority of studies in tropical rainforest canopies being restricted to herbivores on the leaves. Lastly, I investigate body size variation between microhabitats. Since microhabitats vary in a number of qualitative and quantitative factors, I examined whether microhabitat choice has influenced the evolution of the body sizes of the invertebrates that utilise them. I collected 40,374 invertebrates from all five microhabitats, including 10,335 beetles which were sorted to 372 morphospecies. Per unit weight, invertebrate densities on flowers were 10 to 10,000 greater than on new or mature leaves. At the species level, flowers were utilised by an estimated 40% of canopy beetle species, despite constituting just 0.06% of crown biomass. Overlap between microhabitats in species composition was also very low, indicating that each microhabitat is utilised by a relatively unique assemblage. In terms of feeding guild structure, invertebrate communities varied between each microhabitat, largely in relation to the food sources provided. For example, herbivores were found predominantly on new leaves and flowers, but were underrepresented among the invertebrate communities inhabiting the other microhabitats. Fungivores and saprophages however, dominated the communities occupying suspended dead wood. Contrary to expectation, host specificity was equally high between an assemblage of herbivorous beetles on the leaves that interact antagonistically with the host tree, and an assemblage of flower-visitors that interact mutualistically with the host plant. Indeed, both herbivores and non-herbivores on flowers were as host specific as herbivores on leaves. Only species that do not interact directly with the host tree (non-herbivores on the leaves) were significantly more generalised in host use. Consequently, the previous assumption that most host specialists on a tree are herbivores on the leaves is refuted, since half of the host specific species were flower-visitors,