Following Bees and Wasps up Mt. Kilimanjaro: From Diversity and Traits to hidden Interactions of Species Auf den Spuren von Bienen und Wespen auf den Kilimandscharo: Eine Studie über die Diversität, Merkmale und verborgenen Wechselwirkungen zwischen Arten Dissertation zur Erlangung des naturwissenschaftlichen Doktorgrades Julius-Maximilians-Universität Würzburg vorgelegt von Antonia Veronika Mayr geboren in Eschwege Würzburg, 2019 Submitted/Eingereicht 4 April 2019 Members of the doctoral committee/Mitglieder der Promotionskommission Chairperson/Vorsitzender Prof. Dr. Ricarda Scheiner Referee/Gutachter Prof. Dr. Ingolf Steffan-Dewenter Referee /Gutachter Prof. Dr. Alexandra-Maria Klein Defence/Promotionskolloquium 29 May 2019 Date of Receipt of Certificates/Doktorurkunde ausgehändigt am: Die Wissenschaft, richtig verstanden, heilt den Menschen von seinem Stolz- denn sie zeigt ihm seine Grenzen. Albert Schweitzer To all the tiny creatures who had to give their lives for science Table of Contents Affidavit.............................................................................................................................. 1 Summary............................................................................................................................. 3 Zusammenfassung ............................................................................................................ 7 Chapter 1 .......................................................................................................................... 11 General Introduction ................................................................................................ 11 1.1 Global change: impact on biodiversity and ecosystem services ...... 15 1.2 Spatial and temporal changes of biodiversity .................................... 17 1.3 Tropical (mountain) ecosystems and elevational gradients ............. 19 1.4 Study design ............................................................................................ 21 Chapter 2 .......................................................................................................................... 33 Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera ........................................ 33 2.1 Introduction ............................................................................................ 35 2.2 Methods ................................................................................................... 38 2.3 Results ...................................................................................................... 43 2.4 Discussion ............................................................................................... 46 2.5 Conclusions ............................................................................................ 50 2.6 Appendix ................................................................................................. 51 Chapter 3 .......................................................................................................................... 65 Seasonal variation in the ecology of tropical cavity-nesting Hymenoptera ..................................................................................................... 65 3.1 Introduction ............................................................................................ 67 3.2 Methods ................................................................................................... 69 3.3 Results ...................................................................................................... 74 3.4 Discussion ............................................................................................... 80 3.5 Conclusion .............................................................................................. 87 3.6 Appendix ................................................................................................. 88 Chapter 4 .......................................................................................................................... 99 Cryptic species and hidden ecological interactions of halictine bees along an elevational gradient ...................................................................... 99 4.1 Introduction .......................................................................................... 101 4.2 Methods ................................................................................................. 102 4.3 Results .................................................................................................... 108 4.4 Discussion ............................................................................................. 113 4.5 Conclusion ............................................................................................ 119 4.6 Appendix ............................................................................................... 120 Chapter 5 ........................................................................................................................ 127 General Discussion .................................................................................................. 127 5.1 Drivers of biodiversity along spatial and temporal environmental gradients – species, traits and interactions ....................................... 131 5.2 Implications for Kilimanjaro´s biodiversity under global change . 137 5.3 Outlook ................................................................................................. 143 5.4 Conclusion ............................................................................................ 150 General Appendix ......................................................................................................... 151 References ...................................................................................................................... 153 Author Contributions ................................................................................................... 179 Publication List .............................................................................................................. 185 Acknowledgements ....................................................................................................... 187 Affidavit Affidavit I hereby declare that my thesis entitled: „ Following Bees and Wasps up Mt. Kilimanjaro: From Diversity and Traits to hidden Interactions of Species” is the result of my own work. I did not receive any help or support from commercial consultants. All sources and / or materials applied are listed and specified in the thesis. Furthermore I verify that the thesis has not been submitted as part of another examination process neither in identical nor in similar form. Besides I declare that if I do not hold the copyright for figures and paragraphs, I obtained it from the rights holder and that paragraphs and figures have been marked according to law or for figures taken from the internet the hyperlink has been added accordingly. Eidesstattliche Erklärung Hiermit erkläre ich an Eides statt, die Dissertation: „Auf den Spuren von Bienen und Wespen auf den Kilimandscharo: Eine Studie über die Diversität, Merkmale und verborgenen Wechselwirkungen zwischen Arten“, eigenständig, d. h. insbesondere selbständig und ohne Hilfe eines kommerziellen Promotionsberaters, angefertigt und keine anderen, als die von mir angegebenen Quellen und Hilfsmittel verwendet zu haben. Ich erkläre außerdem, dass die Dissertation weder in gleicher noch in ähnlicher Form bereits in einem anderen Prüfungsverfahren vorgelegen hat. Weiterhin erkläre ich, dass bei allen Abbildungen und Texten bei denen die Verwertungsrechte (Copyright) nicht bei mir liegen, diese von den Rechtsinhabern eingeholt wurden und die Textstellen bzw. Abbildungen entsprechend den rechtlichen Vorgaben gekennzeichnet sind sowie bei Abbildungen, die dem Internet entnommen wurden, der entsprechende Hypertextlink angegeben wurde. Würzburg, den Place, Date Signature 1 Following Bees and Wasps up Mt. Kilimanjaro 2 Summary Summary Chapter 1 – General Introduction One of the greatest challenges of ecological research is to predict the response of ecosystems to global change; that is to changes in climate and land use. A complex question in this context is how changing environmental conditions affect ecosystem processes at different levels of communities. To shed light on this issue, I investigate drivers of biodiversity on the level of species richness, functional traits and species interactions in cavity-nesting Hymenoptera. For this purpose, I take advantage of the steep elevational gradient of Mt. Kilimanjaro that shows strong environmental changes on a relatively small spatial scale and thus, provides a good environmental scenario for investigating drivers of diversity. In this thesis, I focus on 1) drivers of species richness at different trophic levels (Chapter 2); 2) seasonal patterns in nest-building activity, life-history traits and ecological rates in three different functional groups and at different elevations (Chapter 3) and 3) changes in cuticular hydrocarbons, pollen composition and microbiomes in Lasioglossum bees caused by climatic variables (Chapter 4). Chapter 2 – Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera Drivers of species richness have been subject to research for centuries. Temperature, resource availability and top-down regulation as well as the impact of land use are