Addis Ababa University School of Graduate Studies
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ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES Department of Zoological Sciences (Insect Sciences Stream) Studies on Insect Diversity and Abundance in the Belette-Gera Forest, South Western Ethiopia By Belay Beyene A Thesis Submitted to the Department of Zoological Sciences Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Biology (Insect Sciences) May, 2016 I Addis Ababa University School of Graduate Studies This is to certify that the thesis prepared by Belay Beyene, titled: “Studies on Insect Diversity and Abundance in the Belette-Gera Forest, South Western Ethiopia”and submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Insect Sciences (Zoology) complies with the regulations of the University and meets the accepted standards with respect to originality and quality. Signed by the examining committee: External Examiner: ______________________ Signature: _________Date: _________ Internal Examiner: _______________________ Signature: _________Date: _________ Principal Adviser: _______________________ Signature: _________ Date: _________ Chair of Department or Graduate Program Coordinator _______________________ I ABSTRACT Studies on Insect Diversity and Abundance at Belette-Gera Forest, South Western Ethiopia Belay Beyene Doctor of Philosophy in Biology (Insect Sciences) Addis Ababa University, 2015/16 Abstract Belette-Gera Forest is one of the Afromontane rain forests in south western Ethiopia. The diversity and abundance of insect communities within the forest are not studied and there is no documentation of the insect fauna of the forest.Iinsects is ecologically important and play valuable role in the ecosystem of Belette-Gera forest. This study identified insect species within the forest and assesssed thier diversity, abundance and distribution among habitats and seasons. Habitat distribution of insect fauna was catagorized into three habitats having different land uses/cover and varying degrees of disturbance; Natural forest habiat, Plantation forest habitat and Wetland habitat. Seasonal distribution of insect fauna was also studied in three seasons; long rain season, long dry season and short rain season. Insect species richness and abundance of insect communities of Belette-Gera forest was investigated along a line transect of 100m × 100m starting from the bottom of the valley to the top of the ridge with sample quadrats of 10m ×10m laid for sampling insects. A total of 1560 insect specimens from 14 orders and 120 families were collected from September 2013 to August 2015 using sweep net trap, beating cloth, pitfall trap and hand picking. Shannon-Wiener diversity index and Evenness were used to measure diversity and abundance of the insects at the family level. The highest insect diversity was observed in the order Coleoptera with Shannon diversity index, Hʹ value of 1.77 and evenness, E value of 0.37. Dermaptera, Ephemeroptera, Mecoptera and Neuroptera were the raret insect orders. Similarly, diversity was measured in each habitat II using Shannon-Wiener species diversity index and Evenness. A total of 620 specimens (39.74 %) in the Natural forest habitat, 472 specimens (30.26 %) in the Wetland habitat and 468 specimens (30 %) in the Plantation forest habitat, were collected. These insects were used to determine the richness of the insect fauna in each habitat type. The highest insect diversity was observed in the Natural forest habitat with (Shannon’s, Hʹ= 2.36) and (Evenness, E = 0.49) followed by Plantation forest habitat (Hʹ= 1.84; E = 0.38) and the lowest were recorded in the Wetland habitat (Hʹ= 1.78; E= 0.37). In addition, the influence of season on the diversity and abundance of insects was computed for two different years (2013/2014 and 2014/2015). Shannon-Wiener species diversity index (H’) and Evenness (E ) were used to measure species diversity and abundance in each season. Paired sample T test was computed to determine the significant differences in insects collected in the rainy and dry seasons. Insect abundance and diversity were significantly different between seasons and in 2013/2014 the highest diversity was recorded in the long rain season with (Hʹvalue of 2.563; E value of 0.563). On the other hand, the lowest diversity was recorded during the short rain season (Hʹ value of 1.234; E value of 0.271). Furthermore, in 2014/2015 the highest diversity was recorded in long rainy season with Shannon’s Hʹvalue of 1.868 and with E value of 0.417. The lowest insect diversity was recorded from short rainy season with Shannon’s Hʹ value 1.57. The diversity and abundance of insect communities varied with respect to habitat type and season. As a result, Wet land habitat, Plantation forest habitat and Natural forest habitat were varied in increasing order with respect to diversity and abundance of insect communities. In addition, Short rainy season, Long dry season and Long rainy season varied in increasing order with respect to of diversity and abundance in the study forest. The variation of insect species diversity and abundance in the habitat types and seasons were the result of III environmental variation (both biotic and abiotic factors), human interference; and the responce of insects to thesef actors influenced the diversity and abumdance of insect communities residing in these habitats in different seasons. Therefore, knowledge on the identity of insect species and factors which influence their diversity and abundance is important as baseline information for further study to assess the different aspects of the insect founa adapted in Belette-Gera forest. Key words: Diversity, abundance, insects, habitat, season IV DECLARATION I, the undersigned, declare that this thesis is my original work and has not been presented for a degree in any other university, and that all sources of materials used for the thesis have been duly acknowledged. Name: Belay Beyene Mekonnen Signature: ________________________ Place: Department of Zoological Sciences Addis Ababa University Date of Submission: May 2016 V ACKNOWLEDGEMENTS First, I would like to thank my principal advisor, Dr. Emana Getu, for his considerable support and guidance throughout the planning and implementation of this research paper. I am enormously grateful for his initiation, guidance, knowledge, experience, great interest, proofreading, and encouragement and for allowing me to conduct this study in a not well- addressed problem area. Furthermore, I thank and appreciate him for his free and friendly approach throughout the study period. I am grateful to Addis Ababa University, Department of Zoological Sciences, for financial support, Laboratory and other provisions. I also thank Samara University for partial financial support of the thesis work and for sponsoring my study. I would like to acknowledge the thematic research of insect sciences stream for their fund on Insect Biodiversity. I would like to thank Belette-Gera National forest officeforhosting my field research and for their technical support in the fieldwork. I would also like to acknowledge Mohammed Abadiga and Galli Abadura who were my field assistants and the local people who supported me in the field study. My sincere thanks go to all my friends and colleagues at Addis Ababa University and Samara University for their help and cooperation at various stages of the study. Finally, I express my conscientious gratitude to my sister Hirut Beyene, my friends Abebech Simel and Temmam Abadilibi who have always been a source of love, encouragement, guidance, unconditional support and patience.Their support during my educational pursuits has been invaluable. Words are inadequate to thank you here. Finally, it is my pleasure to express my deep sense of gratitude to my sonsAmir and Isak for bearing with me at all odds. VI DEDICATION Dedicated to: My sons Amir and Isak, for your sacrifice of time and endless love. VII TABLE OFCONTENTS PAGE DECLARATION .......................................................................................................................................... V DEDICATION ............................................................................................................................................ VII TABLE OFCONTENTS ............................................................................................................................ VIII LIST OF TABLES ....................................................................................................................................... XI LIST OF FIGURES .................................................................................................................................... XIV LIST OF PLATES ....................................................................................................................................... XV LIST OF APPENDICES ............................................................................................................................ XVI Chapter 1 GENERAL INTRODUCTION ..................................................................................................... 1 Chapter 2 GENERAL LITERATURE REVIEW .......................................................................................... 6 2.1. Importance of Biodiversity .................................................................................................................. 6 2.2. Insect Biodiversity ..............................................................................................................................