Pollinator communities and plant-pollinator interactions in fragmented calcareous grasslands Dissertation zur Erlangung des Doktorgrades der Fakultät für Agrarwissenschaften der Georg-August-Universität Göttingen vorgelegt von Birgit Meyer geboren in Varel Göttingen, Juli 2007 D 7 1. Referent: Prof. Dr. Ingolf Steffan-Dewenter 2. Korreferent: Prof. Dr. Stefan Vidal Tag der mündlichen Prüfung: 19.07.07 CONTENTS CHAPTER 1: POLLINATORS IN AGRICULTURAL LANDSCAPES................................................... 1 Introduction .................................................................................................................... 2 Study region and study sites .......................................................................................... 3 Research objectives......................................................................................................... 6 Chapter outline ............................................................................................................... 6 Conclusions...................................................................................................................... 8 CHAPTER 2: IMPORTANCE OF LIFE HISTORY TRAITS FOR POLLINATOR LOSS IN FRAGMENTED CALCAROUS GRASSLANDS...........................................................................10 Abstract ..........................................................................................................................11 Introduction ...................................................................................................................11 Materials and methods..................................................................................................13 Study region............................................................................................................ 13 Habitat and landscape characteristics ..................................................................... 14 Pollinator sampling................................................................................................. 15 Statistical analyses.................................................................................................. 16 Results............................................................................................................................ 17 Habitat area and connectivity ................................................................................. 17 Resource availability .............................................................................................. 18 Effects of landscape matrix .................................................................................... 19 Body size ................................................................................................................ 19 Breeding strategies.................................................................................................. 20 Discussion ...................................................................................................................... 21 Species-area relationship ........................................................................................ 21 Abundance-area relationship .................................................................................. 23 Effects of body size on species-area relationships ................................................. 23 Sociality .................................................................................................................. 24 Cleptoparasitic bees................................................................................................ 24 Connectivity............................................................................................................ 25 Landscape diversity ................................................................................................ 25 Resource availability .............................................................................................. 26 Conservation implications ...................................................................................... 27 CHAPTER 3: CONTRASTING RESPONSES OF SPECIES RICHNESS AND DENSITY OF HOVERFLIES (DIPTERA: SYRPHIDAE) TO AGRICULTURAL LAND-USE CHANGE .................. 30 Abstract ......................................................................................................................... 31 Zusammenfassung ........................................................................................................ 31 Introduction .................................................................................................................. 32 Methods ......................................................................................................................... 33 Study region and site characteristics....................................................................... 33 Pollinator sampling................................................................................................. 34 Statistical analyses.................................................................................................. 35 Results............................................................................................................................ 36 Size and quality of calcarous grasslands ................................................................ 36 Landscape diversity ................................................................................................ 38 Discussion ...................................................................................................................... 39 Conclusions.................................................................................................................... 42 CHAPTER 4: LINKING FLOWER VISITATION, SEED SET, AND SEED PREDATION OF PRIMULA VERIS AT MULTIPLE SPATIAL SCALES ................................................................. 45 Summary ....................................................................................................................... 46 Introduction .................................................................................................................. 46 Methods ......................................................................................................................... 48 Study species .......................................................................................................... 48 Study region and study sites ................................................................................... 48 Flower visitation observation, pollen supplementation, and seed collection ......... 49 Statistical analyses.................................................................................................. 50 Results............................................................................................................................ 51 Pollinator abundance and diversity......................................................................... 51 Seed set and pollination limitation ......................................................................... 54 Seed predation ........................................................................................................ 55 Discussion ...................................................................................................................... 55 Pollinator abundance and richness.......................................................................... 55 Seed set and pollination limitation ......................................................................... 57 Seed predation ........................................................................................................ 58 Spatial scales........................................................................................................... 59 CHAPTER 5: PATCH AND LANDSCAPE EFFECTS ON POLLINATOR DIVERSITY AND SEED SET OF HIPPOCREPIS COMOSA IN AN AGRICULTURAL LANDSCAPE ............................................... 61 Abstract ......................................................................................................................... 62 Zusammenfassung ........................................................................................................ 62 Introduction .................................................................................................................. 63 Materials and methods................................................................................................. 65 Study species and its habitat................................................................................... 65 Study region and study design................................................................................ 65 Flower visitation observation ................................................................................. 66 Pollination experiments .......................................................................................... 67 Statistical analysis................................................................................................... 67 Results............................................................................................................................ 68 Effects of patch size, habitat area, and landscape diversity on flower visitors ...... 68 Pollination of Hippocrepis comosa ........................................................................ 70 Discussion .....................................................................................................................