Summary:
Natural habitat loss and exotic plant invasions are two major drivers of global change in subtropical and tropical ecosystems. These two drivers lead to a loss of biodiversity and alter species interactions, which may imperil vital ecosystem functions and services such as pollination and seed dispersal by animals. Yet, additive and potential interactive effects of natural habitat loss and plant invasion on mutualistic interactions are poorly understood. I therefore studied the combined effects of these two drivers on plant–pollinator and plant–frugivore interactions in a heterogeneous forest landscape in South Africa. The studies presented in this thesis demonstrate that natural habitat loss and exotic plant invasions profoundly alter and partly disrupt plant–animal mutualistic interactions. Specialized species and interactions are especially vulnerable, which may not only affect their own survival but also that of their mutualistic partners. Here, it should be noted that my findings indicate that both studied mutualisms, pollination and seed dispersal, are equally likely to be significantly altered by global change, despite marked differences between them such as the specialization between mutualistic partners. Furthermore, the community approach applied in all of my studies showed that the overall effects of the two global change drivers on the studied mutualism are generally negative, but also allowed me to separate the responses of different species to the two drivers. Here, I showed that these responses were in many cases directly related to the functional traits of species. In contrast, species richness was a poor representative of changes in the functional composition of species communities. Consequently, understanding and predicting ecological processes under global change considerably benefits from functional trait-based approaches. Furthermore, I found that different drivers of global change affect communities via different response traits. Results obtained from one functional trait therefore may not be representative for those from another trait. Similarly, in all of my studies I found marked effects of the two investigated global change drivers on mutualistic interactions and the composition of species communities. However, effects were often specific to one driver, and many results would have been overlooked in single-driver studies. Consequently, my results highlight the need to include multiple global change drivers when studying ecosystem processes on a community scale. Here, I found that the two drivers can be complementary in their negative effects on specialized species and interactions. While these additive effects are already worrying, I also found evidence for negative synergistic effects between the two drivers on specialized species. Such synergisms considerably increase the risk of species’ extinctions and thus of a permanent disruption of essential ecosystem processes.
Bibliographie / References
- Hubbell SP (2001) The unified neutral theory of biodiversity and biogeography. Princeton University Press, Princeton, New Jersey
- Schleuter D, Daufresne M, Massol F, Argillier C (2010) A user's guide to functional diversity indices. Ecol Monogr 80:469–484
- Ne'eman G, Jürgens A, Newstrom-Lloyd L, Potts SG, Dafni A (2010) A framework for comparing pollinator performance: effectiveness and efficiency. Biol Rev 85:435–451
- Pauw A, Hawkins JA (2011) Reconstruction of historical pollination rates reveals linked declines of pollinators and plants. Oikos 120:344–349
- González-Varo JP, Biesmeijer JC, Bommarco R, Potts SG, Schweiger O, Smith HG, Steffan-Dewenter I, Szentgyörgyi H, Woyciechowski M, Vilà M (2013) Combined effects of global change pressures on animal-mediated pollination. Trends Ecol Evol 28:524–530
- Potts SG, Vulliamy B, Dafni A, Ne'eman G, Willmer P (2003) Linking bees and flowers: how do floral communities structure pollinator communities? Ecology 84:2628–2642
- Vitousek PM, Mooney HA, Lubchenco J, Melillo JM (1997) Human domination of earth's ecosystems. Science 277:494–499
- Sala OE, Chapin FS, Armesto JJ, Berlow E, Bloomfield J, Dirzo R, Huber-Sanwald E, Huenneke LF, Jackson RB, Kinzig A, Leemans R, Lodge DM, Mooney HA, Oesterheld M, Poff NL, Sykes MT, Walker BH, Walker M, Wall DH (2000) Global biodiversity scenarios for the year 2100. Science 287:1770–1774
- Deckers B, Verheyen K, Vanhellemont M, Maddens E, Muys B, Hermy M (2008) Impact of avian frugivores on dispersal and recruitment of the invasive Prunus serotina in an agricultural landscape. Biol Invasions 10:717–727
- Herrera CM (1987) Components of pollinator " quality " : comparative analysis of a diverse insect assemblage. Oikos 50:79–90
- Herrera CM (1989) Pollinator abundance, morphology and flower visitation rate: analysis of the " quantity " component in a plant–pollinator system. Oecologia 80:241–248
- Bascompte J, Jordano P, Olesen JM (2006) Asymmetric coevolutionary networks facilitate biodiversity maintenance. Science 312:431–433
- Potts SG, Biesmeijer JC, Kremen C, Neumann P, Schweiger O, Kunin WE (2010) Global pollinator declines: trends, impacts and drivers. Trends Ecol Evol 25:345–353
- Legendre P, Gallagher E (2001) Ecologically meaningful transformations for ordination of species data. Oecologia 129:271–280
- Bascompte J, Jordano P (2007) Plant–animal mutualistic networks: the architecture of biodiversity. Annu Rev Ecol Evol Syst 38:567–593
- Heleno RH, Olesen JM, Nogales M, Vargas P, Traveset A (2013) Seed dispersal networks in the Galápagos and the consequences of alien plant invasions. Proc R Soc B 280:20122112. doi: 10.1098/rspb.2012.2112
- Newbold T, Scharlemann JPW, Butchart SHM, Sekercioglu CH, Alkemade R, Booth H, Purves DW (2013) Ecological traits affect the response of tropical forest bird species to land-use intensity. Proc R Soc B 280:20122131. doi: 10.1098/rspb.2012.2131
- Tilman D, Downing J (1994) Biodiversity and stability in grasslands. Nature 367:363–365
- Dennis AJ, Westcott DA (2006) Reducing complexity when studying seed dispersal at community scales: a functional classification of vertebrate seed dispersers in tropical forests. Oecologia 149:620–634
- Greenleaf SS, Williams NM, Winfree R, Kremen C (2007) Bee foraging ranges and their relationship to body size. Oecologia 153:589–596
- Dietzsch AC, Stanley DA, Stout JC (2011) Relative abundance of an invasive alien plant affects native pollination processes. Oecologia 167:469–479
- Saunders DA, Hobbs RJ, Margules CR (1991) Biological consequences of ecosystem fragmentation: a review. Conserv Biol 5:18–32
- Blüthgen N, Klein A-M (2011) Functional complementarity and specialisation: The role of biodiversity in plant–pollinator interactions. Basic Appl Ecol 12:282–291
- Williams NM, Cariveau D, Winfree R, Kremen C (2011) Bees in disturbed habitats use, but do not prefer, alien plants. Basic Appl Ecol 12:332–341
- Farwig N, Berens DG (2012) Imagine a world without seed dispersers: a review of threats, consequences and future directions. Basic Appl Ecol 13:109–115
- Herrera JM, Doblas-Miranda E (2013) Land-cover change effects on trophic interactions: current knowledge and future challenges in research and conservation. Basic Appl Ecol 14:1–11
- Bjerknes A-L, Totland Ø, Hegland SJ, Nielsen A (2007) Do alien plant invasions really affect pollination success in native plant species? Biol Conserv 138:1–12
- Williams NM, Crone EE, Roulston TH, Minckley RL, Packker L, Potts SG (2010) Ecological and life- history traits predict bee species responses to environmental disturbances. Biol Conserv 143:2280– 2291
- Mouillot D, Graham NAJ, Villéger S, Mason NWH, Bellwood DR (2013) A functional approach reveals community responses to disturbances. Trends Ecol Evol 28:167–177
- Díaz S, Cabido M (2001) Vive la différence: plant functional diversity matters to ecosystem processes. Trends Ecol Evol 16:646–655
- Johnson S, Steiner K (2000) Generalization versus specialization in plant pollination systems. Trends Ecol Evol 15:140–143
- Borcard D, Legendre P (2002) All-scale spatial analysis of ecological data by means of principal coordinates of neighbour matrices. Ecol Model 153:51–68
- Cox P, Elmqvist T (2000) Pollinator extinction in the Pacific islands. Conserv Biol 14:1237–1239 9 – References 132
- MacArthur RH, Pianka ER (1966) On optimal use of a patchy environment. Am Nat 100:603–609
- Stang M, Klinkhamer PGL, Waser NM, Stang I, van der Meijden E (2009) Size-specific interaction patterns and size matching in a plant–pollinator interaction web. Ann Bot 103:1459–1469
- Hargreaves AL, Harder LD, Johnson SD (2012) Floral traits mediate the vulnerability of aloes to pollen theft and inefficient pollination by bees. Ann Bot 109:761–72
- Albrecht J, Berens DG, Blüthgen N, Jaroszewicz B, Selva N, Farwig N (2013) Logging and forest edges reduce redundancy in plant–frugivore networks in an old-growth European forest. J Ecol 101:990–999
- Mouchet MA, Villéger S, Mason NWH, Mouillot D (2010) Functional diversity measures: an overview of their redundancy and their ability to discriminate community assembly rules. Funct Ecol 24:867–876
- Cadotte MW, Carscadden K, Mirotchnick N (2011) Beyond species: functional diversity and the maintenance of ecological processes and services. J Appl Ecol 48:1079–1087
- Spasojevic MJ, Suding KN (2012) Inferring community assembly mechanisms from functional diversity patterns: the importance of multiple assembly processes. J Ecol 100:652–661
- Montero-Castaño A, Vilà M (2012) Impact of landscape alteration and invasions on pollinators: a meta- analysis. J Ecol 100:884–893
- Aguilar R, Ashworth L, Galetto L, Aizen MA (2006) Plant reproductive susceptibility to habitat fragmentation: review and synthesis through a meta-analysis. Ecol Lett 9:968–980
- Perea R, Delibes M, Polko M, Suárez-Esteban A, Fedriani JM (2013) Context-dependent fruit–frugivore interactions: partner identities and spatio-temporal variations. Oikos 122:943–951
- Ghazoul J (2004) Alien abduction: disruption of native plant–pollinator interactions by invasive species. Biotropica 36:156–164
- Cairns CE, Villanueva-Gutiérrez R, Koptur S, Bray DB (2005) Bee populations, forest disturbance, and africanization in Mexico. Biotropica 37:686–692
- Berens DG, Farwig N, Schaab G, Böhning-Gaese K (2008) Exotic guavas are foci of forest regeneration in Kenyan farmland. Biotropica 40:104–112
- Winfree R, Aguilar R, LeBuhn G (2009) A meta-analysis of bees' responses to anthropogenic disturbance. Ecology 90:2068–2076
- McConkey KR, Brockelman WY (2011) Nonredundancy in the dispersal network of a generalist tropical forest tree. Ecology 92:1492–1502
- Fishbein M, Venable DL (1996) Diversity and temporal change in the effective pollinators of Asclepias tuberosa. Ecology 77:1061–1073
- Ehrlich PR, Raven PH (1964) Butterflies and plants: a study in coevolution. Evolution 18:586–608
- Pyšek P, Hulme PE (2005) Spatio-temporal dynamics of plant invasions: linking pattern to process. Ecoscience 12:302–315
- Thébault E, Fontaine C (2010) Stability of ecological communities and the architecture of mutualistic and trophic networks. Science 329:853–856
- Fontaine C, Collin CL, Dajoz I (2008) Generalist foraging of pollinators: diet expansion at high density. J Ecol 96:1002–1010
- King C, Ballantyne G, Willmer PG (2013) Why flower visitation is a poor proxy for pollination: measuring single-visit pollen deposition, with implications for pollination networks and conservation. Methods Ecol Evol 4:811–818
- Aizen MA, Sabatino M, Tylianakis JM (2012) Specialization and rarity predict nonrandom loss of interactions from mutualist networks. Science 335:1486–1489
- Gotelli NJ, Graves GR (1996) Null models in ecology. Smithsonian Institution Press, Washington, D.C.
- Bradley BA, Blumenthal DM, Wilcove DS, Ziska LH (2010) Predicting plant invasions in an era of global change. Trends Ecol Evol 25:310–318
- Morales CL, Traveset A (2009) A meta-analysis of impacts of alien vs. native plants on pollinator visitation and reproductive success of co-flowering native plants. Ecol Lett 12:716–728
- Traveset A, Richardson DM (2006) Biological invasions as disruptors of plant reproductive mutualisms. Trends Ecol Evol 21:208–216
- Moragues E, Traveset A (2005) Effect of Carpobrotus spp. on the pollination success of native plant species of the Balearic Islands. Biol Conserv 122:611–619
- Schupp EW, Jordano P, Gómez JM (2010) Seed dispersal effectiveness revisited: a conceptual review. New Phytol 188:333–353
- Rezende EL, Lavabre JE, Guimarães PR, Jordano P, Bascompte J (2007) Non-random coextinctions in phylogenetically structured mutualistic networks. Nature 448:925–928
- Tylianakis JM, Laliberté E, Nielsen A, Bascompte J (2010) Conservation of species interaction networks. Biol Conserv 143:2270–2279
- Tylianakis JM, Didham RK, Bascompte J, Wardle DA (2008) Global change and species interactions in terrestrial ecosystems. Ecol Lett 11:1351–1363
- Vázquez DP, Morris WF, Jordano P (2005) Interaction frequency as a surrogate for the total effect of animal mutualists on plants. Ecol Lett 8:1088–1094
- Bartomeus I, Vilà M, Santamaría L (2008) Contrasting effects of invasive plants in plant–pollinator networks. Oecologia 155:761–770
- McConkey KR, Prasad S, Corlett RT, Campos-Arceiz A, Brodie JF, Rogers H, Santamaria L (2012) Seed dispersal in changing landscapes. Biol Conserv 146:1–13
- Lehouck V, Spanhove T, Colson L, Adringa-Davis A, Cordeiro NJ, Lens L (2009) Habitat disturbance reduces seed dispersal of a forest interior tree in a fragmented African cloud forest. Oikos 118:1023– 1034
- Terborgh J, Nuñez-Iturri G, Pitman NCA, Valverde, FHC, Alvarez P, Swamy V, Pringle EG, Paine CET (2008) Tree recruitment in an empty forest. Ecology 89:1757–1768
- McGill BJ, Enquist BJ, Weiher E, Westoby M (2006) Rebuilding community ecology from functional traits. Trends Ecol Evol 21:178–185
- Hockey PAR, Dean WR, Ryan P (2005) Roberts Birds of Southern Africa. John Voelcker Bird Book Fund, Cape Town
- Ibanez S (2012) Optimizing size thresholds in a plant–pollinator interaction web: towards a mechanistic understanding of ecological networks. Oecologia 170:233–242
- Grass I, Berens DG, Peter F, Farwig N (2013) Additive effects of exotic plant abundance and land-use intensity on plant–pollinator interactions. Oecologia 173:913–923
- Henderson L (2001) Alien weeds and invasive plants: a complete guide to declared weeds and invaders in South Africa. Agricultural Research Council, Pretoria
- Cornwell WK, Schwilk LDW, Ackerly DD (2006) A trait-based test for habitat filtering: convex hull volume. Ecology 87:1465–1471
- Sodhi NS, Liow LH, Bazzaz FA (2004) Avian extinctions from tropical and subtropical forests. Annu Rev Ecol Evol Syst 35:323–345
- Loreau M, de Mazancourt C (2013) Biodiversity and ecosystem stability: a synthesis of underlying mechanisms. Ecol Lett 16:106–115
- von Maltitz G (2003) Classification system for South African indigenous forests: an objective classification for the Department of Water Affairs and Forestry. Environ. Rep. ENV-P-C 2003-017, CSIR, Pretoria Webb CO, Donoghue MJ (2005) Phylomatic: tree assembly for applied phylogenetics. Mol Ecol Notes 5:181–183
- Pärtel M, Szava-Kovats R, Zobel M (2011) Dark diversity: shedding light on absent species. Trends Ecol Evol 26:124–128
- Borcard D, Legendre P, Avois-Jacquet C, Tuomisto H (2004) Dissecting the spatial structure of ecological data at multiple scales. Ecology 85:1826–1832
- Kearns CA, Inouye DW, Waser NM (1998) Endangered mutualisms: the conservation of plant–pollinator interactions. Annu Rev Ecol Syst 29:83–112
- Farwig N, Böhning-Gaese K, Bleher B (2006) Enhanced seed dispersal of Prunus africana in fragmented and disturbed forests? Oecologia 147:238–252
- Woodhall S (2005) Field guide to butterflies of South Africa. Struik, Cape Town Wotton DM, Kelly D (2011) Frugivore loss limits recruitment of large-seeded trees. Proc R Soc B 278:3345–3354
- Picker M, Griffiths CL, Weaving A (2004) Field guide to insects of South Africa. Struik, Cape Town Pooley E (1998) A field guide to wild flowers KwaZulu-Natal and the eastern region. Natal Flora Publications Trust, Durban
- Pauw A, Stofberg J, Waterman RJ (2009) Flies and flowers in Darwin's race. Evolution 63:268–279
- Jordano P (2000) Fruits and frugivory. In: Fenner M (ed) Seeds: the ecology of regeneration in plant communities. CABI, Wallingford, pp 125–166
- Ollerton J, Winfree R, Tarrant S (2011) How many flowering plants are pollinated by animals? Oikos 120:321–326
- Sekercioglu CH (2006) Increasing awareness of avian ecological function. Trends Ecol Evol 21:464–471
- Breitbach N, Tillmann S, Schleuning M, Grünewald C, Laube I, Steffan-Dewenter I, Böhning-Gaese K (2012) Influence of habitat complexity and landscape configuration on pollination and seed-dispersal interactions of wild cherry trees. Oecologia 168:425–437
- Ezemvelo KZN Wildlife (2011) KwaZulu-Natal land cover 2008 v1.1. Unpublished GIS coverage. Biodiversity Conservation Planning Division, Ezemvelo KZN Wildlife, Cascades, Pietermaritzburg
- Tscharntke T, Sekercioglu CH, Dietsch TV, Sodhi NS, Hoehn P, Tylianakis JM (2008) Landscape contraints on functional diversity of birds and insects in tropical agroecosystems. Ecology 89:944–951
- Baayen RH (2011) languageR: data sets and functions with " Analyzing Linguistic Data: A practical introduction to statistics " . R package version 1.4
- Voigt FA, Arafeh R, Farwig N, Griebeler EM, Böhning-Gaese K (2009) Linking seed dispersal and genetic structure of trees: a biogeographical approach. J Biogeogr 36:242–254
- Bates D, Maechler M, Bolker B (2012) lme4: linear mixed-effects models using S4 classes. R package version 0.999999-0
- Simón-Porcar VI, Santos-Gally R, Arroyo J (2013) Long-tongued insects promote disassortative pollen transfer in style-dimorphic Narcissus papyraceus (Amaryllidaceae). J Ecol doi: 10.1111/1365- 2745.12179
- Blüthgen N, Menzel F, Blüthgen N (2006) Measuring specialization in species interaction networks. BMC Ecol 6:9
- MEA (2005) Millennium Ecosytem Assessment. Ecosytems and human well-being: biodiversity synthesis. World Resources Institute, Washington, D.C.
- Barton K (2013) MuMIn: multi-model inference. R package version 1.9.5
- Dray S, Legendre P, Blanchet G (2011) packfor: forward selection with permutation (Canoco p.46). R package version 0.0-8/r100
- Richardson DM, Allsopp N, D'Antonio CM, Milton SJ, Rejmánek M (2000b) Plant invasions -the role of mutualisms. Biol Rev 75:65–93
- Boon R (2010) Pooley's trees of eastern South Africa. Flora and Fauna Publications Trust, Durban
- Eeley HAC, Lawes MJ, Reyers B (2001) Priority areas for the conservation of subtropical indigenous forest in southern Africa: a case study from KwaZulu-Natal. Biodivers Conserv 10:1221–1246
- Bawa K, Bullock S, Perry D, Coville RE, Grayum MH (1985) Reproductive biology of tropical lowland rain forest trees. II. Pollination systems. Am J Bot 72:346–356
- Aizen MA, Ashworth L, Galetto L (2002) Reproductive success in fragmented habitats: do compatibility systems and pollination specialization matter? J Veg Sci 13:885–892
- Chittenden H (2007) Roberts bird guide: a comprehensive field guide to over 950 birds species in southern Africa. John Voelcker Bird Book Fund, Cape Town
- Stang M, Klinkhamer PGL, van der Meijden E (2006) Size constraints and flower abundance determine the number of interactions in a plant–flower visitor web. Oikos 112:111–121
- Bivand R, Altman M, Anselin L, Assunção R, Berke O, Bernat A, Blanchet G, Blankmeyer E, Carvalho M, Christensen B, Chun Y, Dormann C, Dray S, Halbersma R, Krainski E, Legendre P, Lewin-Koh N, Li H, Ma J, Millo G, Mueller W, Ono H, Peres-Neto P, Piras G, Reder M, Tiefelsdorf M, Yu D (2013) spdep: spatial dependence: weighting schemes, statistics and models. R package version 0.5-56
- Schleuning M, Fründ J, Klein A-M, Abrahamczyk S, Alarcón R, Albrecht M, Andersson GKS, Bazarian S, Böhning-Gaese K, Bommarco R, Dalsgaard B, Dehling DM, Gottlieb A, Hagen M, Hickler T, Holzschuh A, Kaiser-Bunbury CN, Kreft H, Morris RJ, Sandel B, Sutherland WJ, Svenning J-C, Tscharntke T, Watts S, Weiner CN, Werner M, Williams NM, Winqvist C, Dormann CF, Blüthgen N (2012) Specialization of mutualistic interaction networks decreases toward tropical latitudes. Curr Biol 22:1925-1931
- Hoehn P, Tscharntke T, Tylianakis JM, Steffan-Dewenter I (2008) Functional group diversity of bee pollinators increases crop yield. Proc R Soc B 275:2283–2291
- Cooper KH (1985) The conservation status of indigenous forests in Transvaal, Natal and OFS, South Africa. Wildlife Society of Southern Africa, Durban
- Mayfield MM, Bonser SP, Morgan JW, Aubin I, McNamara S, Vesk PA (2010) What does species richness tell us about functional trait diversity? Predictions and evidence for responses of species and functional trait diversity to land-use change. Glob Ecol Biogeogr 19:423–431
- Dicks LV, Corbet SA, Pywell RF (2002) Compartmentalization in plant–insect flower visitor webs. J Anim Ecol 71:32–43
- Richardson DM, Pyšek P, Rejmánek M, Barbour MG, Panetta FD, West CJ (2000a) Naturalization and invasion of alien plants: concepts and definitions. Divers Distrib 6:93–107
- Brosi BJ, Daily GC, Shih TM, Oviedo F, Durán G (2008) The effects of forest fragmentation on bee communities in tropical countryside. J Appl Ecol 45:773–783
- Neuschulz EL, Grass I, Botzat A, Johnson SD, Farwig N (2013) Persistence of flower visitors and pollination services of a generalist tree in modified forests. Austral Ecol 38:374–382
- Cavender-Bares J, Kozak KH, Fine PVA, Kembel SW (2009) The merging of community ecology and phylogenetic biology. Ecol Lett 12:693–715
- Gosper CR, Vivian-Smith G (2009) The role of fruit traits of bird-dispersed plants in invasiveness and week risk assessment. Divers Distrib 15:1037–1046
- Gleditsch JM, Carlo TA (2011) Fruit quantity of invasive shrubs predicts the abundance of common native avian frugivores in central Pennsylvania. Divers Distrib 17:244–253
- Diniz-Filho JAF, Bini LM, Rangel TF, Morales-Castilla I, Olalla-Tárraga MA, Rodriguez MA, Hawkins BA (2012) On the selection of phylogenetic eigenvectors for ecological analyses. Ecography 35:239–249
- Alarcón R (2010) Congruence between visitation and pollen-transport networks in a California plant– pollinator community. Oikos 119:35–44
- Neuschulz EL, Botzat A, Farwig N (2011) Effects of forest modification on bird community composition and seed removal in a heterogeneous landscape in South Africa. Oikos 120:1371–1379
- Mulwa RK, Neuschulz EL, Böhning-Gaese K, Schleuning M (2013) Seasonal fluctuations of resource abundance and avian feeding guilds across forest-farmland boundaries in tropical Africa. Oikos 122:524–532
- Hagen M, Kraemer M (2010) Agricultural surroundings support flower–visitor networks in an Afrotropical rain forest. Biol Conserv 143:1654–1663
- Olesen JM, Eskildsen LI, Venkatasamy S (2002) Invasion of pollination networks on oceanic islands: importance of invader complexes and endemic super generalists. Divers Distrib 8:181–192
- Scholtz C, Holm E (2008) Insects of Southern Africa. Protea Boekhuis, Pretoria
- Aravind NA, Rao D, Ganeshaiah KN, Poulsen JG (2010) Impact of the invasive plant, Lantana camara, on bird assemblages at Malé Mahadeshwara Reserve Forest, South India. Trop Ecol 51:325–338
- Dormann CF, Fründ J, Blüthgen N, Gruber B (2009) Indices, graphs and null models: analyzing bipartite ecological networks. Open Ecol J 2:7–24
- Biesmeijer JC, Roberts SPM, Reemer M, Ohlemüller R, Edwards M, Peeters T, Schaffers AP, Potts SG, Kleukers R, Thomas CD, Settele J, Kunin WE (2006) Parallel declines in pollinators and insect- pollinated plants in Britain and the Netherlands. Science 313:351–354
- Goulson D, Derwent LC (2004) Synergistic interactions between an exotic honeybee and an exotic weed: pollination of Lantana camara in Australia. Weed Res 44:195–202
- Winfree R, Griswold T, Kremen C (2007) Effect of human disturbance on bee communities in a forested ecosystem. Conserv Biol 21:213–223
- Henderson L (2007) Invasive, naturalized and casual alien plants in southern Africa: a summary based on the Southern African Plant Invaders Atlas (SAPIA). Bothalia 37:215–248
- Vilà M, D'Antonio CM (1998) Fruit choice and seed dispersal of invasive vs. noninvasive Carpobrotus (Aizoaceae) in coastal California. Ecology 79:1053–1060
- Blanchet FG, Legendre P, Borcard D (2008) Forward selection of explanatory variables. Ecology 89:2623– 2632
- Laliberté E, Legendre P (2010) A distance-based framework for measuring functional diversity from multiple traits. Ecology 91:299–305
- Vázquez DP, Lomáscolo SB, Maldonado MB, Chacoff NP, Dorado J, Stevani EL, Vitale NL (2012) The strength of plant–pollinator interactions. Ecology 93:719–725
- Legendre P (1993) Spatial autocorrelation: trouble or new paradigm? Ecology 74:1659–1673
- Herrera CM (1984) Adaptation to frugivory of mediterranean avian seed dispersers. Ecology 65:609–617
- Howe HF, Smallwood J (1982) Ecology of seed dispersal. Annu Rev Ecol Syst 13:201–228
- Bernhardt P (1987) A comparison of the diversity, density, and foraging behavior of bees and wasps on Australian Acacia. Ann Missouri Bot Gard 74:42–50
- MacArthur RH, Levins R (1967) The limiting similarity, convergence, and divergence of coexisting species. Am Nat 101:377–385
- Lawes MJ (1990) The distribution of the samango monkey (Cercopithecus mitis erythrarchus Peters, 1852 and Cercopithecus mitis labiatus I. Geoffroy, 1843) and forest history in southern Africa. J Biogeogr 17:669–680
- Costanza R, D'Arge R, de Groot R, Farber S, Grasso M, Hannon B, Limburg K, Naeem S, O'Neill RV, Paruelo J, Raskin RG, Sutton P, van den Belt M (1997) The value of the world's ecosystem services and natural capital. Nature 387:253–260
- Chapin FS, Zavaleta ES, Eviner VT, Naylor RL, Vitousek PM, Reynolds HL, Hooper DU, Lavorel S, Sala OE, Hobbie SE, Mack MC, Díaz S (2000) Consequences of changing biodiversity. Nature 405:234– 242
- Kremen C, Williams NM, Thorp RW (2002) Crop pollination from native bees at risk from agricultural intensification. Proc Natl Acad Sci USA 99:16812–16816
- Memmott J, Waser NM (2002) Integration of alien plants into a native flower–pollinator visitation web. Proc R Soc B 269:2395–2399
- Klein A-M, Vaissière BE, Cane JH, Steffan-Dewenter I, Cunningham SA, Kremen C, Tscharntke T (2007) Importance of pollinators in changing landscapes for world crops. Proc R Soc B 274:303–313
- Jordano P, García C, Godoy J, García-Castaño J (2007) Differential contribution of frugivores to complex seed dispersal patterns. Proc Natl Acad Sci USA 104:3278–3282
- Kissling WD, Rahbek C, Böhning-Gaese K (2007) Food plant diversity as broad-scale determinant of avian frugivore richness. Proc R Soc B 274:799–808
- Aizen MA, Morales CL, Morales JM (2008) Invasive mutualists erode native pollination webs. PLoS Biol 6:1–8
- Vilà M, Bartomeus I, Dietzsch AC, Petanidou T, Steffan-Dewenter I, Stout JC, Tscheulin T (2009) Invasive plant integration into native plant–pollinator networks across Europe. Proc R Soc B 276:3887–3893
- Chama L, Berens DG, Downs CT, Farwig N (2013) Habitat characteristics of forest fragments determine specialisation of plant–frugivore networks in a mosaic forest landscape. PLoS One 8:e54956
- Cadotte MW (2013) Experimental evidence that evolutionarily diverse assemblages result in higher productivity. Proc Natl Acad Sci USA 110:8996–9000
- Myers N (1996) Environmental services of biodiversity. Proc Natl Acad Sci USA 93:2764–2769
- R Development Core Team (2012) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna
- Ghazoul J (2005) Buzziness as usual? Questioning the global pollination crisis. Trends Ecol Evol 20:367– 373
- Didham RK, Tylianakis JM, Gemmell NJ, Rand TA, Ewers RM (2007) Interactive effects of habitat modification and species invasion on native species decline. Trends Ecol Evol 22:489–496
- Kirika JM, Bleher B, Böhning-Gaese K, Chira R, Farwig N (2008) Fragmentation and local disturbance of forests reduce frugivore diversity and fruit removal in Ficus thonningii trees. Basic Appl Ecol 9:663– 672
- Hooper DU, Chapin FS, Ewel JJ, Hector A, Inchausti P, Lavorel S, Lawton JH, Lodge DM, Loreau M, Naeem S, Schmid B, Setälä H, Symstad AJ, Vandermeer J, Wardle DA (2005) Effects of biodiversity on ecosystem functioning: a consensus of current knowledge. Ecol Monogr 75:3–35
- Albrecht M, Schmid B, Hautier Y, Müller CB (2012) Diverse pollinator communities enhance plant reproductive success. Proc R Soc B 279:4845–4852
- Bolker BM, Brooks ME, Clark CJ, et al. (2009) Generalized linear mixed models: a practical guide for ecology and evolution. Trends Ecol Evol 24:127–135
- Fontaine C, Dajoz I, Meriguet J, Loreau M (2006) Functional diversity of plant–pollinator interaction webs enhances the persistence of plant communities. PLoS Biol 4:e1
- Dray S, Dufour A (2007) The ade4 package: implementing the duality diagram for ecologists. J Stat Softw 22:1–20
- Bartomeus I, Vilà M, Steffan-Dewenter I (2010) Combined effects of Impatiens glandulifera invasion and landscape structure on native plant pollination. J Ecol 98:440–450
- Brückmann SV, Krauss J, Steffan-Dewenter I (2010) Butterfly and plant specialists suffer from reduced connectivity in fragmented landscapes. J Appl Ecol 47:799–809
- Steffan-Dewenter I, Münzenberg U, Bürger C, et al. (2002) Scale-dependent effects of landscape context on three pollinator guilds. Ecology 83:1421–1432