This electronic thesis or dissertation has been downloaded from Explore Bristol Research, http://research-information.bristol.ac.uk Author: Forup, Mikael Lytzau Title: The restoration of plant pollinator interactions General rights Access to the thesis is subject to the Creative Commons Attribution - NonCommercial-No Derivatives 4.0 International Public License. A copy of this may be found at https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode This license sets out your rights and the restrictions that apply to your access to the thesis so it is important you read this before proceeding. Take down policy Some pages of this thesis may have been removed for copyright restrictions prior to having it been deposited in Explore Bristol Research. However, if you have discovered material within the thesis that you consider to be unlawful e.g. breaches of copyright (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please contact [email protected] and include the following information in your message: •Your contact details •Bibliographic details for the item, including a URL •An outline nature of the complaint Your claim will be investigated and, where appropriate, the item in question will be removed from public view as soon as possible. The restoration of plant-pollinator interactions MikaeI Lytzau Forup A thesis submitted to the University of Bristol in accordancewith the requirementsof the degreeof Doctor of Philosophy in the Faculty of Science School of Biological Sciences 32,045words January2003 ABSTRACT 1. Restoration schemesare normally evaluatedin terms of whether target species establish. While this is convenient information, it does not reveal how species interact in restoredsystems or how sustainablerestored systems are. 2. This study first investigatedold and restoredhay meadowsand then old and restored lowland heathlands.Sites were comparedand contrastedwith respectto plant-pollinator interactions. Both structural and functional aspectsof the biodiversity were quantified. The latter was done through the application of quantitative food web statistics. 3. Fieldwork involved sampling flower-visiting insects,while laboratory work involved analysis of the pollen carried on insect surfaces.There was considerable variation in community structureamong study sites of both habitats.Despite this variation, the meadowswere functionally similar. For the heathlands,both flower visitation patterns and quantitative pollen transportpatterns differed among study sites. This is concludedpartly to be an artefact of the age of the restoredheathlands that will disappearas they mature. 4. Heathland interaction webs were analysedfor the presenceof compartments. Although such compartmentswere concludedto be atypical for heathlands,the method for compartmentalizationanalysis may not have been suitable for detecting very small web compartments. 5. A study consideredthe impact of honeybeeson bumblebeesand found a negative associationbetween these bees. However, no mechanismwas confirmed to account for this. 6. Thrips pollination was investigatedon the heathlands.Thrips were restoredon all heathlandsand found to affect a significant fraction of the seedset in three hcathland plant spccies. 7. Restoration of plant-pollinator interactions was successful.Although structurally different communities had establishedon restoredsites, study sites belongedto the samebroad habitat categoriesand appearedto function in broadly the sameways. 2 FOR MY FAmiLy Jim said beeswouldn't sting idiots; but I didn't believethat, because I had tried themlots of timesmyself, and they wouldn't sting me. Mark Twain, Adventures of Huckleberry Finn ACKNOWLEDGEMENTS It is a luxury to be able to study something in detail for three years and discover how surprisingly little was known about that something.Ecology is a greatjigsaw puzzle with so many of its pieces still missing. It has been a great privilege to be part of a 'searchteam' here in Bristol. It would not have been possible without funding. Thanks to the British Council for awarding me the British CheveningScholarship that funded the first year of this PhD together with a grant from the Knud Hojgaards Fond, and to the Danish ResearchCouncils for awarding me the scholarship,which funded the other two years.Thanks are also due to the many landowners and site managers,who grantedme accessto their land. Thanks to JaneMemmott for her great support -a remarkablecombination of skill, enthusiasm,professionalism and friendliness. Thanks also to my colleaguesin the research group, the great people who joined us temporarily due to the lack of office spacein the department,and to the people in the wider department.Thanks to my many friends in Bristol for enriching my life. Thanks to my family for their enthusiasmand support - and to Kelly; a great keystone in my life. 4 AUTHOR'S DECLARATION I declare that the work in this dissertationwas carried out in accordancewith the Regulationsof the University of Bristol. The work is original except where indicated by special referencein the text and no part of the dissertationhas been submitted for any other degree.Any views expressedin the dissertationare those of the author and in no way representthose of the University of Bristol. The dissertationhas not beenpresented to any other university for examination either in the United Kingdom or overseas. Mikael Lytzau Forup Bristol, January7th 2003 5 I CONTENTS f Page Abstract 2 Acknowledgments 4 Author's declaration 5 Contents 6 ONE Introduction 11 1.1 Restoration ecology 12 1.2 The 'fuzzy target' and 'moving target' problems 12 1.3 The 'field of dreams' hypothesis 13 1.4 When are ecological restorationscarried out? 15 1.5 Problems in current restoration ecology 16 1.6 Reproductive mutualisms 17 1.7 Food webs and pollination biology 18 1.8 The aim of this study 19 1.9 Meadows and heathlands 19 1.10 Thesis organisation 20 TWO The restoration of plant-pollinator Interactions on hay meadows 21 Summary 22 2.1 Introduction 23 2.11 Restoration of interactions 23 2.12 Interaction webs 23 2.13 Plant-pollinator webs 24 2.14 Aims 24 2.2 Methods 26 2.21 Study sites 26 2.22 Flower visitation webs 26 2.23 Pollen transport webs 27 2.24 Flower groups 28 2.25 Data analysis 28 2.3 Results 31 6 2.31 Was the pattern of insect visitation similar for old and restored 31 meadows? 2.32 Was the pattern of pollen transport similar for old and restored 32 meadows? 2.4 Discussion 34 2.41 The structure of the plant-pol li nation communities on the four sites 34 2.42 The restoration of pollination processes 35 2.43 The use of speciesinteractions in restoration ecology 37 2.44 Limitations in the construction of the webs 37 Table 2.1 - Table 2.7 40 Figure 2.1 - Figure 2.6 43 THREE The restoration of plant-pollinator Interactions on lowland heathlands 49 Summary 50 3.1 Introduction 51 3.11 Dry lowland heath 51 3.12 Heathland pollinators 52 3.13 Heathland restoration 52 3.14 Heathland study sites 53 3.15 Plant-pollinator interactions on old and restoredheathland 53 3.2 Methods 55 3.21 Study sites 55 3.22 Study 1: quantitative flower visitation webs 55 3.23 Study 2: quantitative pollen transport webs 56 3.24 Four models for heathlandrestoration 57 3.25 Statistical analysis 58 3.3 Results 61 3.31 Study 1: quantitative flower visitation data 61 3.32 Entomophilous flower species 61 3.33 Insect community structure 61 3.34 Plant-insect interactions 63 3.35 Visitation patterns 64 3.36 Study 2: quantitative pollen transport data 64 7 3.37 Specialist pollen carriers and redundancy 65 3.38 Pollen-insect interactions 65 3.39 Pollen transport patterns 66 3.4 Discussion 67 3.41 Model summary 67 3.42 The outcome of the restoration schemes 68 3.43 The diversity of insect visitors 69 3.44 The importance of the floral composition 72 3.45 Temporal data 72 3.46 Other limitations 73 Table 3.1 - Table 3.15 74 Figure 3.1 - Figure 3.12 79 FOUR Compartmentalization in heathland webs 90 Summary 91 4.1 Introduction 92 4.11 Compartmentsin food webs 92 4.12 Compartmentsin pollination webs 93 4.2 Methods 94 4.21 The 4-step compartmentalizationanalysis 94 4.22 Step 1: trophic similarity 94 4.23 Step 2: correspondenceanalysis 95 4.24 Step 3: analysis of variance 96 4.25 Step 4: within and betweengroup trophic similarities 96 4.3 Results 98 4.31 Trophic similarities 98 4.32 Compartments 98 4.33 Pairs of species 99 4.34 Multiple compartmentswithin sites 99 4.35 Old and restoredcompartments 99 4.4 Discussion 100 4.41 Compartmentsin heathlandwebs 100 4.42 Why are compartmentsuncommon on heathlands? 100 8 4.43 Observedcompartments 101 4.44 Visitation web and pollen web compartments 102 4.45 Replication and restoration 102 Table 4.1 - Table 4.7 103 Figure 4.1 - Figure 4.2 108 FIVE Competition between honeybeesand bumblebees 110 Summary III 5.1 Introduction 112 5.11 Competition by the honeybee 112 5.12 Bumblebees 113 5.13 Bee competition on old and restoredheathlands 113 5.14 Aims 113 5.2 Methods 115 5.21 Bee association2002 115 5.22 Data analysis 115 5.23 Bee foraging patterns 116 5.24 Rates of increase2001 116 5.3 Results 117 5.31 Bee association2002 117 5.32 Bray-Curtis coefficients for the 2002 data 118 5.33 Bray-Curtis coefficients for the 2001 data 118 5.34 Bees and flower abundancein the 2001 data 119 5.35 Rates of increasein 2001 119 5.4 Discussion 121 5.41 The negative association 121 5.42 Coefficients 121 5.43 Flower abundance 122 5A4