51
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Dáttilo W, Dyer L. Canopy Openness Enhances Diversity of Ant-Plant Interactions in the Brazilian Amazon Rain Forest. Biotropica 2014. [DOI: 10.1111/btp.12157] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wesley Dáttilo
- Instituto de Neuroetología; Universidad Veracruzana; Xalapa Veracruz 91190 Mexico
| | - Lee Dyer
- Department of Biology; University of Nevada; Reno NV 89557-0314 U.S.A
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52
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Martinson HM, Fagan WF. Trophic disruption: a meta-analysis of how habitat fragmentation affects resource consumption in terrestrial arthropod systems. Ecol Lett 2014; 17:1178-89. [PMID: 24866984 DOI: 10.1111/ele.12305] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 12/21/2013] [Accepted: 05/08/2014] [Indexed: 11/29/2022]
Abstract
Habitat fragmentation is a complex process that affects ecological systems in diverse ways, altering everything from population persistence to ecosystem function. Despite widespread recognition that habitat fragmentation can influence food web interactions, consensus on the factors underlying variation in the impacts of fragmentation across systems remains elusive. In this study, we conduct a systematic review and meta-analysis to quantify the effects of habitat fragmentation and spatial habitat structure on resource consumption in terrestrial arthropod food webs. Across 419 studies, we found a negative overall effect of fragmentation on resource consumption. Variation in effect size was extensive but predictable. Specifically, resource consumption was reduced on small, isolated habitat fragments, higher at patch edges, and neutral with respect to landscape-scale spatial variables. In general, resource consumption increased in fragmented settings for habitat generalist consumers but decreased for specialist consumers. Our study demonstrates widespread disruption of trophic interactions in fragmented habitats and describes variation among studies that is largely predictable based on the ecological traits of the interacting species. We highlight future prospects for understanding how changes in spatial habitat structure may influence trophic modules and food webs.
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Affiliation(s)
- Holly M Martinson
- Department of Entomology, University of Maryland, College Park, MD, 20742, USA
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53
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Rodewald AD, Rohr RP, Fortuna MA, Bascompte J. Community-level demographic consequences of urbanization: an ecological network approach. J Anim Ecol 2014; 83:1409-17. [PMID: 24702202 DOI: 10.1111/1365-2656.12224] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 03/27/2014] [Indexed: 11/27/2022]
Abstract
Ecological networks are known to influence ecosystem attributes, but we poorly understand how interspecific network structure affect population demography of multiple species, particularly for vertebrates. Establishing the link between network structure and demography is at the crux of being able to use networks to understand population dynamics and to inform conservation. We addressed the critical but unanswered question, does network structure explain demographic consequences of urbanization? We studied 141 ecological networks representing interactions between plants and nesting birds in forests across an urbanization gradient in Ohio, USA, from 2001 to 2011. Nest predators were identified by video-recording nests and surveyed from 2004 to 2011. As landscapes urbanized, bird-plant networks were more nested, less compartmentalized and dominated by strong interactions between a few species (i.e. low evenness). Evenness of interaction strengths promoted avian nest survival, and evenness explained demography better than urbanization, level of invasion, numbers of predators or other qualitative network metrics. Highly uneven networks had approximately half the nesting success as the most even networks. Thus, nest survival reflected how urbanization altered species interactions, particularly with respect to how nest placement affected search efficiency of predators. The demographic effects of urbanization were not direct, but were filtered through bird-plant networks. This study illustrates how network structure can influence demography at the community level and further, that knowledge of species interactions and a network approach may be requisite to understanding demographic responses to environmental change.
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Affiliation(s)
- Amanda D Rodewald
- School of Environment and Natural Resources, 2021 Coffey Road, The Ohio State University, Columbus, OH, 43210, USA
| | - Rudolf P Rohr
- Integrative Ecology Group, Estación Biológica de Doñana , CSIC C/ Americo Vespucio s/n, Sevilla, E-41092, Spain
| | - Miguel A Fortuna
- Integrative Ecology Group, Estación Biológica de Doñana , CSIC C/ Americo Vespucio s/n, Sevilla, E-41092, Spain
| | - Jordi Bascompte
- Integrative Ecology Group, Estación Biológica de Doñana , CSIC C/ Americo Vespucio s/n, Sevilla, E-41092, Spain
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54
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Fabian Y, Sandau N, Bruggisser OT, Aebi A, Kehrli P, Rohr RP, Naisbit RE, Bersier LF. Plant diversity in a nutshell: testing for small-scale effects on trap nesting wild bees and wasps. Ecosphere 2014. [DOI: 10.1890/es13-00375.1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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55
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Complementary molecular information changes our perception of food web structure. Proc Natl Acad Sci U S A 2014; 111:1885-90. [PMID: 24449902 DOI: 10.1073/pnas.1316990111] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
How networks of ecological interactions are structured has a major impact on their functioning. However, accurately resolving both the nodes of the webs and the links between them is fraught with difficulties. We ask whether the new resolution conferred by molecular information changes perceptions of network structure. To probe a network of antagonistic interactions in the High Arctic, we use two complementary sources of molecular data: parasitoid DNA sequenced from the tissues of their hosts and host DNA sequenced from the gut of adult parasitoids. The information added by molecular analysis radically changes the properties of interaction structure. Overall, three times as many interaction types were revealed by combining molecular information from parasitoids and hosts with rearing data, versus rearing data alone. At the species level, our results alter the perceived host specificity of parasitoids, the parasitoid load of host species, and the web-wide role of predators with a cryptic lifestyle. As the northernmost network of host-parasitoid interactions quantified, our data point exerts high leverage on global comparisons of food web structure. However, how we view its structure will depend on what information we use: compared with variation among networks quantified at other sites, the properties of our web vary as much or much more depending on the techniques used to reconstruct it. We thus urge ecologists to combine multiple pieces of evidence in assessing the structure of interaction webs, and suggest that current perceptions of interaction structure may be strongly affected by the methods used to construct them.
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56
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Mokross K, Ryder TB, Côrtes MC, Wolfe JD, Stouffer PC. Decay of interspecific avian flock networks along a disturbance gradient in Amazonia. Proc Biol Sci 2013; 281:20132599. [PMID: 24335983 DOI: 10.1098/rspb.2013.2599] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Our understanding of how anthropogenic habitat change shapes species interactions is in its infancy. This is in large part because analytical approaches such as network theory have only recently been applied to characterize complex community dynamics. Network models are a powerful tool for quantifying how ecological interactions are affected by habitat modification because they provide metrics that quantify community structure and function. Here, we examine how large-scale habitat alteration has affected ecological interactions among mixed-species flocking birds in Amazonian rainforest. These flocks provide a model system for investigating how habitat heterogeneity influences non-trophic interactions and the subsequent social structure of forest-dependent mixed-species bird flocks. We analyse 21 flock interaction networks throughout a mosaic of primary forest, fragments of varying sizes and secondary forest (SF) at the Biological Dynamics of Forest Fragments Project in central Amazonian Brazil. Habitat type had a strong effect on network structure at the levels of both species and flock. Frequency of associations among species, as summarized by weighted degree, declined with increasing levels of forest fragmentation and SF. At the flock level, clustering coefficients and overall attendance positively correlated with mean vegetation height, indicating a strong effect of habitat structure on flock cohesion and stability. Prior research has shown that trophic interactions are often resilient to large-scale changes in habitat structure because species are ecologically redundant. By contrast, our results suggest that behavioural interactions and the structure of non-trophic networks are highly sensitive to environmental change. Thus, a more nuanced, system-by-system approach may be needed when thinking about the resiliency of ecological networks.
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Affiliation(s)
- Karl Mokross
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, , 227 RNR Building, LSU, Baton Rouge, LA 70803-6202, USA, Projeto Dinâmica Biológica de Fragmentos Florestais, INPA, , R. André Araújo 2936, Caixa postal 478, Petrópolis, Manaus, Amazonas 69083-000, Brazil, Smithsonian Conservation Biology Institute, , National Zoological Park, PO Box 37012-MRC 5503, Washington, DC 20013, USA, Departamento de Ecologia, Universidade Estadual Paulista, , Rio Claro, São Paulo 13506-900, Brazil
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57
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Fabian Y, Sandau N, Bruggisser OT, Aebi A, Kehrli P, Rohr RP, Naisbit RE, Bersier LF. The importance of landscape and spatial structure for hymenopteran-based food webs in an agro-ecosystem. J Anim Ecol 2013; 82:1203-14. [PMID: 23863136 DOI: 10.1111/1365-2656.12103] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Accepted: 05/12/2013] [Indexed: 11/26/2022]
Abstract
1. Understanding the environmental factors that structure biodiversity and food webs among communities is central to assess and mitigate the impact of landscape changes. 2. Wildflower strips are ecological compensation areas established in farmland to increase pollination services and biological control of crop pests and to conserve insect diversity. They are arranged in networks in order to favour high species richness and abundance of the fauna. 3. We describe results from experimental wildflower strips in a fragmented agricultural landscape, comparing the importance of landscape, of spatial arrangement and of vegetation on the diversity and abundance of trap-nesting bees, wasps and their enemies, and the structure of their food webs. 4. The proportion of forest cover close to the wildflower strips and the landscape heterogeneity stood out as the most influential landscape elements, resulting in a more complex trap-nest community with higher abundance and richness of hosts, and with more links between species in the food webs and a higher diversity of interactions. We disentangled the underlying mechanisms for variation in these quantitative food web metrics. 5. We conclude that in order to increase the diversity and abundance of pollinators and biological control agents and to favour a potentially stable community of cavity-nesting hymenoptera in wildflower strips, more investment is needed in the conservation and establishment of forest habitats within agro-ecosystems, as a reservoir of beneficial insect populations.
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Affiliation(s)
- Yvonne Fabian
- Unit of Ecology & Evolution, University of Fribourg, Chemin du Musée 10, 1700, Fribourg, Switzerland
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58
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Karp DS, Moeller HV, Frishkoff LO. Nonrandom extinction patterns can modulate pest control service decline. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2013; 23:840-849. [PMID: 23865234 DOI: 10.1890/12-0937.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Changes in biodiversity will mediate the consequences of agricultural intensification and expansion for ecosystem services. Regulating services, like pollination and pest control, generally decline with species loss. In nature, however, relationships between service provision and species richness are not always strong, partially because anthropogenic disturbances purge species from communities in nonrandom orders. The same traits that make for effective service providers may also confer resistance or sensitivity to anthropogenic disturbances, which may either temper or accelerate declines in service provision with species loss. We modeled a community of predators interacting with insect pest prey, and identified the contexts in which pest control provision was most sensitive to species loss. We found pest populations increased rapidly when functionally unique and dietary-generalist predators were lost first, with up to 20% lower pest control provision than random loss. In general, pest abundance increased most in the scenarios that freed more pest species from predation. Species loss also decreased the likelihood that the most effective service providers were present. In communities composed of species with identical traits, predators were equally effective service providers and, when competing predators went extinct, remaining community members assumed their functional roles. In more realistic trait-diverse communities, predators differed in pest control efficacy, and remaining predators could not fully compensate for the loss of their competitors, causing steeper declines in pest control provision with predator species loss. These results highlight diet breadth in particular as a key predictor of service provision, as it affects both the way species respond to and alter their environments. More generally, our model provides testable hypotheses for predicting how nonrandom species loss alters relationships between biodiversity and pest control provision.
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Affiliation(s)
- Daniel S Karp
- Center for Conservation Biology, Stanford University, Stanford, California 94305, USA.
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59
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Plein M, Längsfeld L, Neuschulz EL, Schultheiß C, Ingmann L, Töpfer T, Böhning-Gaese K, Schleuning M. Constant properties of plant–frugivore networks despite fluctuations in fruit and bird communities in space and time. Ecology 2013; 94:1296-306. [DOI: 10.1890/12-1213.1] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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60
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Coudrain V, Herzog F, Entling MH. Effects of habitat fragmentation on abundance, larval food and parasitism of a spider-hunting wasp. PLoS One 2013; 8:e59286. [PMID: 23516622 PMCID: PMC3597609 DOI: 10.1371/journal.pone.0059286] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 02/13/2013] [Indexed: 11/26/2022] Open
Abstract
Habitat fragmentation strongly affects species distribution and abundance. However, mechanisms underlying fragmentation effects often remain unresolved. Potential mechanisms are (1) reduced dispersal of a species or (2) altered species interactions in fragmented landscapes. We studied if abundance of the spider-hunting and cavity-nesting wasp Trypoxylon figulus Linnaeus (Hymenoptera: Crabronidae) is affected by fragmentation, and then tested for any effect of larval food (bottom up regulation) and parasitism (top down regulation). Trap nests of T. figulus were studied in 30 agricultural landscapes of the Swiss Plateau. The sites varied in the level of isolation from forest (adjacent, in the open landscape but connected, isolated) and in the amount of woody habitat (from 4 % to 74 %). We recorded wasp abundance (number of occupied reed tubes), determined parasitism of brood cells and analysed the diversity and abundance of spiders that were deposited as larval food. Abundances of T. figulus were negatively related to forest cover in the landscape. In addition, T. figulus abundances were highest at forest edges, reduced by 33.1% in connected sites and by 79.4% in isolated sites. The mean number of spiders per brood cell was lowest in isolated sites. Nevertheless, structural equation modelling revealed that this did not directly determine wasp abundance. Parasitism was neither related to the amount of woody habitat nor to isolation and did not change with host density. Therefore, our study showed that the abundance of T. figulus cannot be fully explained by the studied trophic interactions. Further factors, such as dispersal and habitat preference, seem to play a role in the population dynamics of this widespread secondary carnivore in agricultural landscapes.
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Affiliation(s)
- Valérie Coudrain
- Research Station Agroscope Reckenholz-Tänikon ART, Zürich, Switzerland.
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61
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Bohan DA, Raybould A, Mulder C, Woodward G, Tamaddoni-Nezhad A, Bluthgen N, Pocock MJ, Muggleton S, Evans DM, Astegiano J, Massol F, Loeuille N, Petit S, Macfadyen S. Networking Agroecology. ADV ECOL RES 2013. [DOI: 10.1016/b978-0-12-420002-9.00001-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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62
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63
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64
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Dependence of Brood Cell Length on Nesting Cavity Width in Xylicolous Solitary Wasps of Genera Ancistrocerus and Symmorphus (Hymenoptera: Vespidae). ACTA ACUST UNITED AC 2012. [DOI: 10.2478/v10043-010-0010-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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65
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Joern A, Laws AN. Ecological mechanisms underlying arthropod species diversity in grasslands. ANNUAL REVIEW OF ENTOMOLOGY 2012; 58:19-36. [PMID: 22830354 DOI: 10.1146/annurev-ento-120811-153540] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Arthropods are an important component of grassland systems, contributing significantly to biodiversity and ecosystem structure and function. Climate, fire, and grazing by large herbivores are important drivers in grasslands worldwide. Arthropod responses to these drivers are highly variable and clear patterns are difficult to find, but responses are largely indirect with respect to changes in resources, species interactions, habitat structure, and habitat heterogeneity resulting from interactions among fire, grazing, and climate. Here, we review these ecological mechanisms influencing grassland arthropod diversity. We summarize hypotheses describing species diversity at local and regional scales and then discuss specific factors that may affect arthropod diversity in grassland systems. These factors include direct and indirect effects of grazing, fire, and climate, species interactions, above- and belowground interactions, and landscape-level effects.
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Affiliation(s)
- Anthony Joern
- Division of Biology, Kansas State University, Manhattan, Kansas 66506, USA.
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66
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Lohaus K, Vidal S, Thies C. Farming practices change food web structures in cereal aphid-parasitoid-hyperparasitoid communities. Oecologia 2012; 171:249-59. [PMID: 22736196 PMCID: PMC3538122 DOI: 10.1007/s00442-012-2387-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 05/24/2012] [Indexed: 11/25/2022]
Abstract
Agricultural intensification has been shown to result in a decline in biodiversity across many taxa, but the changes in community structure and species interactions remain little understood. We have analysed and compared the structure of feeding interactions for cereal aphids and their primary and secondary parasitoids in organically and conventionally managed winter wheat fields using quantitative food web metrics (interaction evenness, generality, vulnerability, link density). Despite little variation in the richness of each trophic group, food web structures between the two farming systems differed remarkably. In contrast to common expectations, aphids and primary parasitoids were characterized by (1) a higher evenness of interaction frequencies (interaction evenness) in conventional fields, which cascaded to interactions at the next trophic level, with (2) a higher interaction evenness, (3) a higher ratio of primary parasitoid taxa per secondary parasitoid (generality) and (4) a higher link density. Aphid communities in the organically managed fields almost exclusively consisted of a single ear-colonizing species, Sitobion avenae, while highly fertilized conventional fields were mainly infested by leaf-colonizing aphids that benefit from the nutritional status of winter wheat. In conclusion, agricultural intensification appears to foster the complexity of aphid-parasitoid food webs, thereby not supporting the general expectation on the importance of organic farming practices for species richness and food web complexity.
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Affiliation(s)
- Katharina Lohaus
- Department of Crop Sciences, Entomology, Georg-August-University Göttingen, Göttingen, Germany.
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67
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Agricultural intensification and cereal aphid-parasitoid-hyperparasitoid food webs: network complexity, temporal variability and parasitism rates. Oecologia 2012; 170:1099-109. [PMID: 22644050 PMCID: PMC3496544 DOI: 10.1007/s00442-012-2366-0] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 05/07/2012] [Indexed: 11/25/2022]
Abstract
Agricultural intensification (AI) is currently a major driver of biodiversity loss and related ecosystem functioning decline. However, spatio-temporal changes in community structure induced by AI, and their relation to ecosystem functioning, remain largely unexplored. Here, we analysed 16 quantitative cereal aphid–parasitoid and parasitoid–hyperparasitoid food webs, replicated four times during the season, under contrasting AI regimes (organic farming in complex landscapes vs. conventional farming in simple landscapes). High AI increased food web complexity but also temporal variability in aphid–parasitoid food webs and in the dominant parasitoid species identity. Enhanced complexity and variability appeared to be controlled bottom-up by changes in aphid dominance structure and evenness. Contrary to the common expectations of positive biodiversity–ecosystem functioning relationships, community complexity (food-web complexity, species richness and evenness) was negatively related to primary parasitism rates. However, this relationship was positive for secondary parasitoids. Despite differences in community structures among different trophic levels, ecosystem services (parasitism rates) and disservices (aphid abundances and hyperparasitism rates) were always higher in fields with low AI. Hence, community structure and ecosystem functioning appear to be differently influenced by AI, and change differently over time and among trophic levels. In conclusion, intensified agriculture can support diverse albeit highly variable parasitoid–host communities, but ecosystem functioning might not be easy to predict from observed changes in community structure and composition.
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68
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Kaartinen R, Roslin T. High temporal consistency in quantitative food web structure in the face of extreme species turnover. OIKOS 2012. [DOI: 10.1111/j.1600-0706.2012.20108.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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69
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Rzanny M, Voigt W. Complexity of multitrophic interactions in a grassland ecosystem depends on plant species diversity. J Anim Ecol 2012; 81:614-27. [DOI: 10.1111/j.1365-2656.2012.01951.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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70
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Hagen M, Kissling WD, Rasmussen C, De Aguiar MA, Brown LE, Carstensen DW, Alves-Dos-Santos I, Dupont YL, Edwards FK, Genini J, Guimarães PR, Jenkins GB, Jordano P, Kaiser-Bunbury CN, Ledger ME, Maia KP, Marquitti FMD, Mclaughlin Ó, Morellato LPC, O'Gorman EJ, Trøjelsgaard K, Tylianakis JM, Vidal MM, Woodward G, Olesen JM. Biodiversity, Species Interactions and Ecological Networks in a Fragmented World. ADV ECOL RES 2012. [DOI: 10.1016/b978-0-12-396992-7.00002-2] [Citation(s) in RCA: 236] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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71
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Multitrophic effects of experimental changes in plant diversity on cavity-nesting bees, wasps, and their parasitoids. Oecologia 2011; 169:453-65. [DOI: 10.1007/s00442-011-2205-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 11/08/2011] [Indexed: 11/25/2022]
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72
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Gagic V, Tscharntke T, Dormann CF, Gruber B, Wilstermann A, Thies C. Food web structure and biocontrol in a four-trophic level system across a landscape complexity gradient. Proc Biol Sci 2011; 278:2946-53. [PMID: 21325327 DOI: 10.1098/rspb.2010.2645] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Decline in landscape complexity owing to agricultural intensification may affect biodiversity, food web complexity and associated ecological processes such as biological control, but such relationships are poorly understood. Here, we analysed food webs of cereal aphids, their primary parasitoids and hyperparasitoids in 18 agricultural landscapes differing in structural complexity (42-93% arable land). Despite little variation in the richness of each trophic group, we found considerable changes in trophic link properties across the landscape complexity gradient. Unexpectedly, aphid-parasitoid food webs exhibited a lower complexity (lower linkage density, interaction diversity and generality) in structurally complex landscapes, which was related to the dominance of one aphid species in complex landscapes. Nevertheless, primary parasitism, as well as hyperparasitism, was higher in complex landscapes, with primary parasitism reaching levels for potentially successful biological control. In conclusion, landscape complexity appeared to foster higher parasitism rates, but simpler food webs, thereby casting doubt on the general importance of food web complexity for ecosystem functioning.
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Affiliation(s)
- Vesna Gagic
- Department of Crop Science, Agroecology, Georg-August-University, Grisebachstrasse 6, 37077 Göttingen, Germany.
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73
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74
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Albrecht M, Riesen M, Schmid B. Plant-pollinator network assembly along the chronosequence of a glacier foreland. OIKOS 2010. [DOI: 10.1111/j.1600-0706.2010.18376.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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75
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Schüepp C, Herrmann JD, Herzog F, Schmidt-Entling MH. Differential effects of habitat isolation and landscape composition on wasps, bees, and their enemies. Oecologia 2010; 165:713-21. [PMID: 20730546 DOI: 10.1007/s00442-010-1746-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Accepted: 06/27/2010] [Indexed: 10/19/2022]
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76
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Petermann JS, Müller CB, Weigelt A, Weisser WW, Schmid B. Effect of plant species loss on aphid-parasitoid communities. J Anim Ecol 2010; 79:709-20. [DOI: 10.1111/j.1365-2656.2010.01674.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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77
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Holzschuh A, Steffan-Dewenter I, Tscharntke T. How do landscape composition and configuration, organic farming and fallow strips affect the diversity of bees, wasps and their parasitoids? J Anim Ecol 2009; 79:491-500. [PMID: 20015213 DOI: 10.1111/j.1365-2656.2009.01642.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Habitat destruction and increasing land use intensity result in habitat loss, fragmentation and degradation, and subsequently in the loss of species diversity. The fact that these factors are often highly confounded makes disentangling their effects extremely difficult, if not impossible, and their relative impact on species loss is mostly speculative. 2. In a two-year study, we analysed the relative importance of changed landscape composition (increased areas of cropped habitats), reduced habitat connectivity and reduced habitat quality on nest colonization of cavity-nesting bees, wasps and their parasitoids. We selected 23 pairs of conventional and organic wheat fields in the centre of landscape circles (500 m radius) differing in edge densities (landscape configuration) and % non-crop habitats (landscape composition). Standardized trap nests were established in the field centres and in neighbouring permanent fallow strips (making a total of 92 nesting sites). 3. Factors at all three scales affected nest colonization. While bees were enhanced by high proportions of non-crop habitat in the landscape, wasps profited from high edge densities, supporting our hypothesis that wasps are enhanced by connecting corridors. Colonization of herbivore-predating wasps was lower in field centres than in fallow strips for conventional sites, but not for organic sites, indicating a fallow-like connectivity value of organic fields. The relative importance of habitat type and farming system varied among functional groups suggesting that their perception of crop-non-crop boundaries or the availability of their food resources differed. 4. Local and landscape effects on parasitoids were mainly mediated by their hosts. Parasitism rates were marginally affected by local factors. A specialist parasitoid was more sensitive to high land use intensity than its host, whereas generalist parasitoids were less sensitive. 5. We conclude that the conversion of cropland into non-crop habitat may not be a sufficiently successful strategy to enhance wasps or other species that suffer more from isolation than from habitat loss. Interestingly, habitat connectivity appeared to be enhanced by both higher edge densities and by organic field management. Thus, we conclude that high proportions of conventionally managed and large crop fields threaten pollination and biological control services at a landscape scale.
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Affiliation(s)
- Andrea Holzschuh
- Agroecology, Georg-August University, Waldweg 26, D-37073 Göttingen, Germany.
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78
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Hinners SJ, Hjelmroos-Koski MK. Receptiveness of Foraging Wild Bees to Exotic Landscape Elements. AMERICAN MIDLAND NATURALIST 2009. [DOI: 10.1674/0003-0031-162.2.253] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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79
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Memmott J. Food webs: a ladder for picking strawberries or a practical tool for practical problems? Philos Trans R Soc Lond B Biol Sci 2009; 364:1693-9. [PMID: 19451120 DOI: 10.1098/rstb.2008.0255] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
While food webs have provided a rich vein of research material over the last 50 years, they have largely been the subject matter of the pure ecologist working in natural habitats. While there are some notable exceptions to this trend, there are, as I explain in this paper, many applied questions that could be answered using a food web approach. The paper is divided into two halves. The first half provides a brief review of six areas where food webs have begun to be used as an applied tool: restoration ecology, alien species, biological control, conservation ecology, habitat management and global warming. The second half outlines five areas in which a food web approach could prove very rewarding: urban ecology, agroecology, habitat fragmentation, cross-habitat food webs and ecosystem services.
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Affiliation(s)
- Jane Memmott
- School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK.
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80
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Henson KSE, Craze PG, Memmott J. The restoration of parasites, parasitoids, and pathogens to heathland communities. Ecology 2009; 90:1840-51. [DOI: 10.1890/07-2108.1] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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81
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Ings TC, Montoya JM, Bascompte J, Blüthgen N, Brown L, Dormann CF, Edwards F, Figueroa D, Jacob U, Jones JI, Lauridsen RB, Ledger ME, Lewis HM, Olesen JM, van Veen FJF, Warren PH, Woodward G. Ecological networks--beyond food webs. J Anim Ecol 2009; 78:253-69. [PMID: 19120606 DOI: 10.1111/j.1365-2656.2008.01460.x] [Citation(s) in RCA: 652] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. A fundamental goal of ecological network research is to understand how the complexity observed in nature can persist and how this affects ecosystem functioning. This is essential for us to be able to predict, and eventually mitigate, the consequences of increasing environmental perturbations such as habitat loss, climate change, and invasions of exotic species. 2. Ecological networks can be subdivided into three broad types: 'traditional' food webs, mutualistic networks and host-parasitoid networks. There is a recent trend towards cross-comparisons among network types and also to take a more mechanistic, as opposed to phenomenological, perspective. For example, analysis of network configurations, such as compartments, allows us to explore the role of co-evolution in structuring mutualistic networks and host-parasitoid networks, and of body size in food webs. 3. Research into ecological networks has recently undergone a renaissance, leading to the production of a new catalogue of evermore complete, taxonomically resolved, and quantitative data. Novel topological patterns have been unearthed and it is increasingly evident that it is the distribution of interaction strengths and the configuration of complexity, rather than just its magnitude, that governs network stability and structure. 4. Another significant advance is the growing recognition of the importance of individual traits and behaviour: interactions, after all, occur between individuals. The new generation of high-quality networks is now enabling us to move away from describing networks based on species-averaged data and to start exploring patterns based on individuals. Such refinements will enable us to address more general ecological questions relating to foraging theory and the recent metabolic theory of ecology. 5. We conclude by suggesting a number of 'dead ends' and 'fruitful avenues' for future research into ecological networks.
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Affiliation(s)
- Thomas C Ings
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
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82
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Holzschuh A, Steffan-Dewenter I, Tscharntke T. Grass strip corridors in agricultural landscapes enhance nest-site colonization by solitary wasps. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2009; 19:123-132. [PMID: 19323177 DOI: 10.1890/08-0384.1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Corridors that connect otherwise isolated habitats have often been proposed as a management strategy to mitigate negative effects of habitat fragmentation. Non-crop corridors may have the potential to enhance the connectivity for arthropod predators in cropland landscapes, especially for species that require multiple habitats, such as cavity-nesting wasps which use wooded habitat for nesting and grassland habitat for foraging. However, the effects of corridors in nonexperimental landscapes have been rarely examined. We studied the species richness and abundance of cavity-nesting wasps and their parasitoids in standardized trap nests located in three habitat types (forest edge, hedge, grass strip) and in three grass-strip types (connected to a forest edge, slightly isolated, highly isolated from a forest edge). Species richness and the abundance of wasps (Hymenoptera: Sphecidae, Eumenidae, Pompilidae) were highest at forest edges, which provide natural nesting sites, and lowest in grass strips, with few natural nesting sites. Wasp abundance in grass strips connected to forest edges was 270% higher than in slightly isolated grass strips and 600% higher than in highly isolated grass strips. The abundance of caterpillar-hunting eumenid wasps was 600% higher in connected grass strips than in slightly and highly isolated grass strips. Species richness of wasps was enhanced by 180% in connected grass strips compared to highly isolated grass strips. Parasitism rates were not directly influenced by habitat or grass-strip type, but increased with increasing parasitoid diversity that was higher at forest edges than in grass strips. We conclude that grass-strip corridors enhance the colonization of nesting sites, presumably by facilitating wasp movements. In agricultural landscapes, where nesting sites are limited and food availability changes frequently, rapid colonization of nests may enhance population viability. Higher wasp abundance in connected nesting sites may be directly linked to higher biocontrol of pest caterpillars within the foraging range around nests. Although grass strips can reduce the negative effects of habitat fragmentation, non-crop habitats such as forest habitats and hedges providing nesting sites are required within the home range of wasps to allow reproduction in agricultural landscapes.
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Affiliation(s)
- Andrea Holzschuh
- Agroecology, Georg-August University, Waldweg 26, D-37073 Göttingen, Germany.
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83
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Tylianakis JM, Didham RK, Bascompte J, Wardle DA. Global change and species interactions in terrestrial ecosystems. Ecol Lett 2008; 11:1351-63. [PMID: 19062363 DOI: 10.1111/j.1461-0248.2008.01250.x] [Citation(s) in RCA: 1154] [Impact Index Per Article: 72.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The main drivers of global environmental change (CO2 enrichment, nitrogen deposition, climate, biotic invasions and land use) cause extinctions and alter species distributions, and recent evidence shows that they exert pervasive impacts on various antagonistic and mutualistic interactions among species. In this review, we synthesize data from 688 published studies to show that these drivers often alter competitive interactions among plants and animals, exert multitrophic effects on the decomposer food web, increase intensity of pathogen infection, weaken mutualisms involving plants, and enhance herbivory while having variable effects on predation. A recurrent finding is that there is substantial variability among studies in both the magnitude and direction of effects of any given GEC driver on any given type of biotic interaction. Further, we show that higher order effects among multiple drivers acting simultaneously create challenges in predicting future responses to global environmental change, and that extrapolating these complex impacts across entire networks of species interactions yields unanticipated effects on ecosystems. Finally, we conclude that in order to reliably predict the effects of GEC on community and ecosystem processes, the greatest single challenge will be to determine how biotic and abiotic context alters the direction and magnitude of GEC effects on biotic interactions.
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Affiliation(s)
- Jason M Tylianakis
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand.
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84
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Blüthgen N, Fründ J, Vázquez DP, Menzel F. WHAT DO INTERACTION NETWORK METRICS TELL US ABOUT SPECIALIZATION AND BIOLOGICAL TRAITS. Ecology 2008; 89:3387-99. [PMID: 19137945 DOI: 10.1890/07-2121.1] [Citation(s) in RCA: 243] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Nico Blüthgen
- Department of Animal Ecology and Tropical Biology, Biozentrum, University of Würzburg, Am Hubland, Würzburg 97074, Germany.
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