IMPACTS OF DEFORESTATION ON MOSQUITO COMMUNITY DYNAMICS Hayley Louise Brant Imperial College London Centre for Environmental Policy, Faculty of Natural Sciences, Silwood Park Campus, Buckhurst Road, Ascot, SL5 7PY, UK Thesis submitted for the degree of Doctor of Philosophy September 2015 2 Declaration of Originality I hereby certify that all content of this thesis is my original research and collaborations with other researchers are fully acknowledged. The experimental design, data collection and analysis of Chapter 5 was completed jointly with Borame Dickens, a fellow researcher at the Centre for Environmental Policy. We both contributed equally to this chapter. Hayley Brant Names of supervisors Professor John Mumford Dr Robert Ewers Copyright declaration The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. 3 Abstract Human-induced land use changes, including deforestation, agricultural encroachment and urbanisation, have caused widespread change in the global distribution of organisms and caused considerable declines in biodiversity through loss of habitat. Oil palm is one of the most rapidly expanding crops in Southeast Asia, but the impact of this crop on mosquito distribution, behaviour and exposure potential has been poorly explored. Understanding these factors is essential for developing, optimising and evaluating novel control measures aimed at reducing disease-transmission. This thesis explored the effect of land use change along an anthropogenic disturbance gradient (primary forest, disturbed forest, highly disturbed forest, oil palm plantations and rural housing estates) in Sabah, Malaysia. The community composition of anthropogenic mosquitoes was separated across land use, with the biggest difference seen between primary forest and oil palm plantations. This was largely driven by medically important mosquitoes attracted to oil palm plantations. Differences in community composition were also seen in areas of rural housing in comparison to primary and disturbed forest sites, due to a high presence of the dengue vector, Stegomyia albopicta, in housing areas. A higher abundance of anopheline vectors were found landing on humans in the disturbed forest and oil palm plantations then primary forest. This thesis found no difference between highly disturbed forest and oil palm plantation sites. This thesis also investigated the host-seeking behaviour of simian malaria vectors, by carrying out human landing catches at ground and canopy level across land use. Results demonstrated the potential ability of one of the vectors, Anopheles balabacensis, to transmit the simian malaria (Plasmodium knowlesi) between canopy-dwelling simian hosts and ground-dwelling humans, and that anthropogenic disturbance increases the abundance of the disease vector. Finally, this thesis investigated the use of different marking methods and the need for an improved dispersal experiment to be carried out. 4 Acknowledgements This research was made possible by a Natural Environment Research Council (NERC) funded PhD studentship and financial support from the Stability of Altered Forest Ecosystems (S.A.F.E. project). I am extremely grateful to the Sabah Biodiversity Council (SaBC), the Royal Society Southeast Asia Rainforest Research Project (SEARRP), Maliau Basin Management Committee (MBMC), Danum Valley Management Committee (DVMC), Yayasan Sabah, Benta Wawasan, National Institute of Health (NIH), Institute for Medical Research (IMR), Medical Research and Ethics Committee (MREC) and the Ministry of Health (MOH) in Malaysia for research permits and permissions to carry out fieldwork. I would like to thank Dr Glen Reynolds, Dr Abdul Fatah Amir and Dr Suzan Benedick for their support during the research permit application process. I would like to thank all the S.A.F.E Project staff in Malaysia. I would like to thank the coordinators, MinSheng Khoo, Sarah Watson and Ryan Gray, for sorting out logistical problems, and my main research assistants, Mus, Mai, Harbin and Zinin for their help during mosquito collections. Thanks to Anand Nainar, Dr Terhi Riutta and Steven Hardwick for sending climate data, and to Rajeev Pillay for allowing me to borrow a laser rangefinder in the field. Thanks to the researchers I crossed over with in the field, especially the ones that left food for me after a long evening in the field. A special thanks to Unding for his help with tree climbing, and for training my research assistants. I would like to extend my thanks to the University of Malaya for their hospitality whilst I stayed in Kuala Lumpur. Thanks to Prof Rohela Mahmud for allowing me to work in her faculty, and to Dr Indra Vythilingam for allowing me to work in her laboratory. Thanks to her students for showing me around Kuala Lumpur. I am especially grateful to the Natural History Museum (NHM) for allowing me laboratory space and for helping me with my identifications. I am indebted to Dr Ralph Harbach for his assistance with sample identification, and to Theresa Howard, Dr Erica McAlister, Dr Duncan Sivell and Dr Daniel Whitmore for allowing me to work in the Diptera department. Thanks to the NHM volunteers for the tea breaks. I would like to express my deep gratitude to my supervisors, Prof John Mumford and Dr Robert Ewers, for their support and advice throughout the entirety of the thesis. Also to Dr Indra Vythilingam, Dr Chris Drakeley, Dr Jeffrey Hii, Dr Tilly Collins and Dr Donald Quicke for their valuable advice, for which I am extremely grateful. Lastly, I would like to thank my family and friends for supporting me through the PhD, especially Laurence- for everything. 5 Contents Declaration of Originality ............................................................................................ 3 Names of supervisors ............................................................................................. 3 Copyright declaration .............................................................................................. 3 Abstract ...................................................................................................................... 4 Acknowledgements .................................................................................................... 5 Chapter 1 – General Introduction ............................................................................. 15 1.1. Overview ..................................................................................................... 15 1.2. Global environmental change and land use change ................................... 15 1.2.1. Tropical deforestation and oil palm expansion in Southeast Asia ......... 16 1.3. Human movement, land use change and mosquito-borne diseases ............. 17 1.4. Mosquito biology ......................................................................................... 21 1.4.1. Host-seeking behaviour and dispersal .................................................. 22 1.5. Mosquito-borne diseases in Malaysia ......................................................... 23 1.5.1. Dengue ................................................................................................. 26 1.5.2. Japanese encephalitis, lymphatic filariasis and chikungunya ............... 26 1.5.3. Malaria .................................................................................................. 27 1.6. Thesis structure and research questions .................................................... 31 Chapter 2 – The Effects of Land Use Change on Mosquito Community Composition ................................................................................................................................. 33 2.1. Abstract ....................................................................................................... 33 2.2. Introduction ................................................................................................. 34 2.3. Methods ...................................................................................................... 36 2.3.1. Study site .............................................................................................. 36 2.3.2. Human landing catches ........................................................................ 39 2.3.3. Ovitraps ................................................................................................ 41 2.3.4. Meteorological data .............................................................................. 41 2.3.5. Data analysis ........................................................................................ 41 2.3.6. Ethics .................................................................................................... 42 2.4. Results ........................................................................................................ 42 2.4.1. Mosquito abundance ............................................................................ 42 2.4.2. Effect of land use on mosquito abundance and presence .................... 48 2.4.3. Community composition ....................................................................... 52 6 2.5. Discussion ..................................................................................................