BEE DIVERSITY AND THEIR FLORAL RESOURCE UTILIZATION ALONG A DISTANCE GRADIENT FROM THE ARABUKO SOKOKE FOREST By Kenneth Njoroge Mwangi (BSc. University of Nairobi) A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science in Biology of Conservation School of Biological Sciences, University of Nairobi 2009 University of NAIROBI Library DECLARATION This Thesis is my original work and has not been presented for award of a degree in any other University Kenneth Njoroge Mwangi Signed................ M & W '................................................... Date.................... V./eifiMD. ....Oil.Dil.MJ.. This thesis has been submitted as original work with our approval as university supervisors Dr. Paul N. Ndegwa Dr. Evans M. Mwangi Signed . ......< trr!w ?r................ Date d e d ic a t io n This work is dedicated to my wonderful, loving, and supportive parents Joseph and Loise For their foresight, belief in the power of education and constant inspiration table of co n ten ts declaration .......................................................................................................................:— II DEDICATION................................................................................................................................. Ill LIST OF FIGURES..........................................................................................................................VI LIST OF TABLES..........................................................................................................................vil ACKNOWLEDGEMENT.............................................................................................................. IX ABSTRACT.......................................................................................................................................x CHAPTER O N E .................................................................................................................................. 1 1.0 INTRODUCTION AND LITERATURE REVIEW......................................................... 1 1.1 Introduction............................................................................................................................1 1.2 Literature review...................................................................................................................4 1.2.1 Conservation of Kenyan forests...................................................................................... 4 1.2.2 Plants - Pollinators Interactions...................................................................................... 7 1.2.3 Bees and pollination......................................................................................................... 8 1.2.4 Interaction among bee species on the floral resources................................................. 11 1.2.5 Threats to bee populations.............................................................................................13 1.3 Justification..........................................................................................................................13 1.4 Research Hypothesis...........................................................................................................14 1.5 Objectives............................................................................................................................14 CHAPTER T W O ...............................................................................................................................15 2.0 MATERIALS AND METHODS.......................................................................................15 2.1 Study A rea........................... 15 2.1.2 Rainfall and Temperature.............................................................................................. 15 2.1.3 Topography and Soils.................................................................................................... 15 2.1.4 Flora................................. 16 2.1.5 Fauna................................................................................................................................16 2.1.6 Threats to the Arabuko Sokoke Forest.......................................................................... 18 2.1.7 Farmland Characteristics............................................................................................... 19 2.2 The study design.................................................................................................................19 2.2.1 Sampling bees................................................................................................................. 19 2.2.2 Surveying the flowering plants and floral abundance..................................................21 2.3 Data Analysis..................................................................................................................... 22 CHAPTER TH R EE.......................................................................................................................... 24 A. 3.0 RESULTS............................. 24 3.1 Bee abundance and diversity.............................................................................................24 3.2 Bee abundance and diversity across a distance gradient from the forest margins....... 24 3.2.1 Bee composition along a distance gradient from the forest margins......................... 25 3.3 Bee abundance and diversity among the three vegetation types.....................................27 3.3.1 Bee composition among the three vegetation types.....................................................28 3.4 Floral resource utilization across a distance gradient from the forest margins............... 29 3.4.1 Trophic niche overlap across a distance gradient from the forest margins................33 CHAPTER FOUR..............................................................................................................................36 4.0 DISCUSSION, CONCLUSIONS, AND RECOMENDATIONS..................................36 4.1 Discussion........................................................................................................................... 36 4.2 Conclusions......................................................................................................................... 42 4.3 Recommendations.............................................................................................................. 43 REFERENCES...................................................................................................................................45 APPENDICES....................................................................................................................................56 list of figures Figure 1 Vegetation types found within the Arabuko Sokoke forest....................................... ... 17 Figure 2 Location of the sampling sites along a distance gradient from the Arabuko Sokoke forest.................................................................................................................................................... 20 Figure 3 Mean abundance (± SE) of five bee genera across a distance gradient from the Arabuko Sokoke forest.......................................................................................................................................27 Figure 4 Mean bee species diversity among the three vegetation types of the Arabuko Sokoke forest (October 2007 - April 2008)....................................................................................................28 Figure 5 Ranking of plant families according by their utilization by bees species around the Arabuko Sokoke forest....................................................................................................................... 31 vi V LIST OF TABLES Table 1 Mean number of bee and species per sampling plot (±SE) in the seven months of the study around the Arabuko-Sokoke forest (October 2007-April 2008).........................................24 Table 2 Mean number of bees and species per sampling plot (±S.E) across a distance gradient from the Arabuko-Sokoke forest margins (October 2007-April 2008).........................................25 Table 3 Mean bee diversity per sampling plot along the distance gradient from the Arabuko Sokoke forest margins........................................................................................................................25 Table 4 Similarity in species composition along the distance gradient from the Arabuko Sokoke forest, based on Horn’s similarity index...........................................................................................26 Table 5 Mean number of honeybees and solitary bees per sampling plot (±S.E) along a distance gradient from the Arabuko-Sokoke forest margins (October 2007-April 2008).......................... 26 Table 6 Mean number of bees and species per sampling plot (±S.E) in the three vegetation types of the Arabuko-Sokoke forest (October 2007-April 2008)............................................................27 Table 7 Similarity in species composition among the three vegetation types of the Arabuko Sokoke forest, based on Horn’s similarity index............................................................................. 28 Table 8 Mean number of honeybees and solitary bees per sampling plot (±S.E) in the three vegetation types of the Arabuko-Sokoke forest (October 2007-April 2008)................................29