37 results on '"Hamback, Peter A."'
Search Results
2. Associational Resistance: Insect Damage to Purple Loosestrife Reduced in Thickets of Sweet Gale
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Hamback, Peter A., Agren, Jon, and Ericson, Lars
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- 2000
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3. Winter Herbivory by Voles during a Population Peak: The Relative Importance of Local Factors and Landscape Pattern
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Hamback, Peter A., Schneider, Michael, and Oksanen, Tarja
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- 1998
4. Lineage-specific targets of positive selection in three leaf beetles with different defence capacity against a parasitic wasp
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Yang, Xuyue, primary, Wheat, Christopher, additional, Slotte, Tanja, additional, and Hamback, Peter, additional
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- 2022
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5. Different spatial structure of plant-associated fungal communities above- and belowground
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Faticov, Maria, Abdelfattah, Ahmed, Hamback, Peter, Roslin, Tomas, and Tack, Ayco J. M.
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Ecology - Abstract
The distribution and community assembly of above- and belowground microbial communities associated with individual plants remain poorly understood, despite its consequences for plant-microbe interactions and plant health. Depending on how microbial communities are structured, we can expect different effects of the microbial community on the health of individual plants and on ecosystem processes. Importantly, the relative role of different factors will likely differ with the scale examined. Here, we address the driving factors at a landscape level, where each individual unit (oak trees) is accessible to a joint species pool. This allowed to quantify the relative effect of environmental factors and dispersal on the distribution of two types of fungal communities: those associated with the leaves and those associated with the soil of Quercus robur trees in a landscape in southwestern Finland. Within each community type, we compared the role of microclimatic, phenological, and spatial variables, and across community types, we examined the degree of association between the respective communities. Most of the variation in the foliar fungal community was found within trees, whereas soil fungal community composition showed positive spatial autocorrelation up to 50 m. Microclimate, tree phenology, and tree spatial connectivity explained little variation in the foliar and soil fungal communities. Foliar and soil fungal communities differed strongly in community structure, with no significant concordance detected between them. We provide evidence that foliar and soil fungal communities assemble independent of each other and are structured by different ecological processes.
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- 2023
6. The role of inputs of marine wrack and carrion in sandy-beach ecosystems: A global review
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Hyndes, Glenn A, Berdan, Emma L., Duarte, Cristian, Dugan, Jenifer E, Emery, Kyle A, Hamback, Peter A, Henderson, Christopher J, Hubbard, David M, Lastra, Mariano, Mateo, Miguel A, Olds, Andrew, Schlacher, Thomas A, Hyndes, Glenn A, Berdan, Emma L., Duarte, Cristian, Dugan, Jenifer E, Emery, Kyle A, Hamback, Peter A, Henderson, Christopher J, Hubbard, David M, Lastra, Mariano, Mateo, Miguel A, Olds, Andrew, and Schlacher, Thomas A
- Abstract
Sandy beaches are iconic interfaces that functionally link the ocean with the land via the flow of organic matter from the sea. These cross-ecosystem fluxes often comprise uprooted seagrass and dislodged macroalgae that can form substantial accumulations of detritus, termed ‘wrack’, on sandy beaches. In addition, the tissue of the carcasses of marine animals that regularly wash up on beaches form a rich food source (‘carrion’) for a diversity of scavenging animals. Here, we provide a global review of how wrack and carrion provide spatial subsidies that shape the structure and functioning of sandy-beach ecosystems (sandy beaches and adjacent surf zones), which typically have little in situ primary production. We also examine the spatial scaling of the influence of these processes across the broader land- and seascape, and identify key gaps in our knowledge to guide future research directions and priorities. Large quantities of detrital kelp and seagrass can flow into sandy-beach ecosystems, where microbial decomposers and animals process it. The rates of wrack supply and its retention are influenced by the oceanographic processes that transport it, the geomorphology and landscape context of the recipient beaches, and the condition, life history and morphological characteristics of the macrophyte taxa that are the ultimate source of wrack. When retained in beach ecosystems, wrack often creates hotspots of microbial metabolism, secondary productivity, biodiversity, and nutrient remineralization. Nutrients are produced during wrack breakdown, and these can return to coastal waters in surface flows (swash) and aquifers discharging into the subtidal surf. Beach-cast kelp often plays a key trophic role, being an abundant and preferred food source for mobile, semi-aquatic invertebrates that channel imported algal matter to predatory invertebrates, fish, and birds. The role of beach-cast marine carrion is likely to be underestimated, as it can be consumed rapidly by highly m
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- 2022
7. Comment on Bohmann et al. Strategies for sample labelling and library preparation in DNA metabarcoding studies
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Hamback, Peter, primary, Sargac, Jasmina, additional, and Grudzinska-Sterno, Magdalena, additional
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- 2022
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8. Management-dependent effects of pollinator functional diversity on apple pollination services: A response-effect trait approach
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Roquer-Beni, Laura, Alins, Georgina, Arnan, Xavier, Boreux, Virginie, Garcia, Daniel, Hamback, Peter A., Klein, Alexandra-Maria, Minarro, Marcos, Vilches, Mario Porcel, Porcel Vilchez, Mario, Rodrigo, Anselm, Samnegard, Ulrika, Tasin, Marco, and Bosch, Jordi
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Ecology - Abstract
Functional traits mediate the response of communities to disturbances (response traits) and their contribution to ecosystem functions (effect traits). To predict how anthropogenic disturbances influence ecosystem services requires a dual approach including both trait concepts. Here, we used a response-effect trait conceptual framework to understand how local and landscape features affect pollinator functional diversity and pollination services in apple orchards. We worked in 110 apple orchards across four European regions. Orchards differed in management practices. Low-intensity (LI) orchards were certified organic or followed close-to-organic practices. High-intensity (HI) orchards followed integrated pest management practices. Within each management type, orchards encompassed a range of local (flower diversity, agri-environmental structures) and landscape features (orchard and pollinator-friendly habitat cover). We measured pollinator visitation rates and calculated trait composition metrics based on 10 pollinator traits. We used initial fruit set as a measure of pollination service. Some pollinator traits (body size and hairiness) were negatively related to orchard cover and positively affected by pollinator-friendly habitat cover. Bee functional diversity was lower in HI orchards and decreased with increased landscape orchard cover. Pollination service was not associated with any particular trait but increased with pollinator trait diversity in LI orchards. As a result, LI orchards with high pollinator trait diversity reached levels of pollination service similar to those of HI orchards. Synthesis and applications. Pollinator functional diversity enables pollinator communities to respond to agricultural intensification and to increase pollination function. Our results show that efforts to promote biodiversity provide greater returns in low-intensity than in high-intensity orchards. The fact that low-intensity orchards with high pollinator functional diversity reach levels of pollination services similar to those of high-intensity orchards provides a compelling argument for the conversion of high-intensity into low-intensity farms.
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- 2021
9. Predatory arthropod community composition in apple orchards: Orchard management, landscape structure and sampling method
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Hamback, Peter A., Porcel Vilches, Mario, Tasin, Marco, and Samnegard, Ulrika
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Agricultural Science - Abstract
Studies on predatory arthropods in agricultural areas seldom include Diptera other than hoverflies, partly because common sampling methods are less effective for capturing species that easily fly off when disturbed. To study the effect from this bias when describing the predator community, we compared traditional beat sampling of branches and suction sampling for describing the community of predatory arthropods in Swedish apple orchards, both organic orchards and orchards using integrated pest management (IPM). Our results indicate that the proportion of both predatory dipterans and parasitic hymenopterans increase dramatically when using suction sampling (Diptera: 32% vs. 20%, Hymenoptera: 25% vs. 7%). In fact, predatory dipterans were the most abundant predatory group when using suction sampling, in contrast to beat sampling where spiders were the most abundant group. One group of predatory flies that was particularly rich in both species and individuals in the surveyed apple orchards was dance flies in the family Hybotidae. Even though the bias of sampling method was evident, it was encouraging that the method choice did not affect the conclusions concerning management on predatory arthropod communities. With both methods, dipteran and coleopteran predators were more abundant in organic apple orchards whereas opilionids were more abundant in orchards managed according to IPM. The inclusion of landscape variables further indicated effects of landscape diversity and of deciduous forest cover, but the response varied in sign between predatory groups. Whereas both Coleoptera and Heteroptera were more abundant in orchards surrounded by more complex landscapes (high landscape diversity and/or high deciduous forest cover), spiders, opilionids and dipterans were rather less abundant in these orchards. To conclude, our study points to the potential importance of predatory dipterans in apple orchards, and we highly recommend future studies of arthropod predators in apple and other crops to actively include predatory Diptera.
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- 2021
10. Coastal niches for terrestrial predators: a stable isotope study
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Mellbrand, Kajsa and Hamback, Peter A.
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Baltic Sea -- Environmental aspects ,Coastal ecosystems -- Observations ,Predation (Biology) -- Research ,Arthropoda -- Food and nutrition ,Zoology and wildlife conservation - Abstract
The purpose of this study was to identify the use of marine versus terrestrial food items by terrestrial arthropod predators on Baltic Sea shores. The inflow of marine nutrients in the area consists mainly of marine algal detritus and emerging aquatic insects (e.g., chironomids). Diets of coastal arthropods were examined using carbon and nitrogen stable isotope analysis in a two source mixing model. The results suggest that spiders are the terrestrial predators mainly utilizing nutrients and energy of marine origin on Baltic Sea shores, whereas insect predators such as beetles and heteropterans mainly utilize nutrients and energy derived from terrestrial sources, possibly owing to differences in hunting behaviour. That spiders are the predators which benefit the most from the marine inflow suggest that eventual effects of marine subsidies for the coastal ecosystem as a whole are likely mediated by spiders. L'objectif de notre etude est de determiner l'utilisation relative des sources alimentaires marines et terrestres par les arthropodes terrestres predateurs sur les cotes de la Baltique. L'apport de nutriments marins dans la region consiste en des debris d'algues marines et d'insectes aquatiques (par ex., des chironomides) qui emergent. Nous examinons les regimes alimentaires d'arthropodes cotiers a l'aide d'une analyse des isotopes stables de carbone et d'azote dans un modele de melange a deux sources. Nos resultats indiquent que les araignees sont des predateurs terrestres qui utilisent surtout des nutriments et de l'energie d'origine marine sur les cotes de la Baltique, alors que les insectes predateurs, tels que les coleopteres et les heteropteres, utilisent surtout des nutriments et de l'energie provenant des sources terrestres, peut-etre a cause de differences dans leurs comportements de chasse. Le fait que les araignees soient les predateurs qui beneficient le plus des apports marins indique que les effets eventuels des apports marins sur l'ecosysteme cotier dans son ensemble se font vraisemblablement par l'intermediaire des araignees. [Traduit par la Redaction], Introduction Many terrestrial predators are known to aggregate in large numbers along shorelines and by various water bodies around the world (Polis et al. 1997, 2004; Sanzone et al. 2003). [...]
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- 2010
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11. Responses of a specialist and a generalist seed predator to variation in their common resource
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Ostergard, Hannah, Hamback, Peter A., and Ehrlen, Johan
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Beetles ,Seeds ,Environmental issues - Abstract
To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.17540.x Byline: Hannah Ostergard, Peter A. Hamback, Johan Ehrlen Abstract: Fluctuations of resources in time and space will influence not only species abundance but also interactions among species. For plant-consumer interactions, the effects of resource variation have mostly been studied in systems with high resource variability. Systems with moderate variations are less studied, although ecological and evolutionary dynamics of plants and consumers are likely to be affected also by less extreme variability. The effects of variation in a particular resource should depend on consumer diet width. We examined how spatial and temporal variation in seed production in the perennial herb Lathyrus vernus influenced population dynamics and resource utilization in two beetle pre-dispersal seed predators with different host ranges over six years. The monophagous Apion opeticum occupied fewer patches and had lower densities than the oligophagous Bruchus atomarius. The proportion of seeds attacked increased with increases in seed production between years for both seed predators. A possible explanation for these patterns is that population dynamics of beetles are driven largely by local factors and that the same factors influence both beetle performance and seed production. In B. atomarius, patterns may also be influenced by a more pronounced preference for L. vernus in years with a high seed production in L. vernus. We conclude that relatively modest variation in seed production may result in responses that differ in both direction and extent from those usually observed in systems with high variation in seed production. Article History: Manuscript Accepted 3 April 2009 Article note: H. Ostergard, P. A. Hamback and J. Ehrlen (ehrlen@botan.su.se), Dept of Botany, Stockholm Univ., Lilla Frescativ. 5, SE-106 91 Stockholm, Sweden.
- Published
- 2009
12. Effects of body size, trophic mode and larval habitat on Diptera stoichiometry: a regional comparison
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Hamback, Peter A., Gilbert, James, Schneider, Katie, Martinson, Holly M., Kolb, Gundula, and Fagan, William F.
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Animal behavior -- Analysis ,Environmental issues - Abstract
To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1600-0706.2009.17177.x Byline: Peter A. Hamback, James Gilbert, Katie Schneider, Holly M. Martinson, Gundula Kolb, William F. Fagan Abstract: Ecological stoichiometry has emerged as a tool for exploring nutrient demand and evolutionary responses to nutrient limitation. Previous studies of insects have found predictable variability in stoichiometry, both in relation to body size and trophic mode, at ordinal levels or higher. Our study further examines the evolutionary and ecological lability in these traits by comparing the effects of body size, trophic mode (larval and adult) and larval habitat on the stoichiometry of insects within one order (Diptera). The study also expands on previous work by analyzing trophic mode both at coarse (detritivore, herbivore, predator) and fine (high- vs low- nutrient quality resources within trophic categories) scales and by comparing nutrient stoichiometry in two geographical regions, Sweden and Arizona. As predicted, adults feeding on nectar or pollen had the lowest body N content in the dataset. Additionally, for Diptera with predatory larvae, species low N diets had lower body N content than those with high N diets. However, body N content was not consistently lower for all species with low N resources, as species feeding on plant material were indistinguishable in stoichiometry from predators with high N diets. We suggest that these results emerge because larval resource exploitation is poorly understood in herbivorous Diptera species. Body P content for Swedish Diptera decreased with body size for all trophic modes, and the only difference among trophic modes was that blood feeders had higher P content than other groups. The regional comparison further showed that the allometry of body P content is a labile trait that may vary at regional scales, as there was no allometric scaling of body P content in the Arizona data set, in contrast to the Swedish data set. These results are not easily explained by existing theoretical frameworks, but instead point to a general context-dependence of P stoichiometry, which should now be a focus for future work. Article History: Manuscript Accepted 29 October 2008 Article note: P. A. Hamback (peter.hamback@botan.su.se) and G. Kolb, Dept of Botany, Stockholm Univ., SE-106 91 Stockholm, Sweden. - J. Gilbert, K. Schneider, H. M. Martinson and W. F. Fagan, Dept of Biology, Univ. of Maryland, College Park, MD 20742, USA.
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- 2009
13. Herbivore-induced 'rent rise' in the host plant may drive a diet breadth enlargement in the tenant
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Stenberg, Johan A., Hamback, Peter A., and Ericson, Lars
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Herbivores -- Influence ,Plant immunology -- Natural history ,Plant immunology -- Causes of ,Plant-pathogen relationships -- Natural history ,Plant-animal interactions -- Influence ,Biological sciences ,Environmental issues - Abstract
Inter- and intraspecies variations in host plant traits are presumably involved in many host shifts by insect herbivores, and elucidating the mechanisms involved in such shifts has been a crucial goal in insect-plant research for several decades. Here we propose that herbivore-induced evolutionary increases in host plant resistance may cause oligophagous insect herbivores to shift to other sympatric plants as currently preferred host plants become increasingly unpalatable. We tested this hypothesis in a system based on the perennial herb Filipendula ulmaria (Rosaceae), whose herbivory defense has become gradually stronger due to prolonged selection by Galerucella tenella (Coleoptera: Chrysomelidae) herbivory in a boreal archipelago. We show that Galerucella gradually increases its use of the alternative host plant Rubus arcticus (Rosaceae) in parallel to gradually increased resistance in Filipendula. Our results imply that, by driving the evolutionary increase in Filipendula resistance, Galerucella is also gradually making the original host species more unpalatable and thereby driving its own host-breadth enlargement. We argue that such self-inflicted 'rent rises' may be an important mechanism behind host plant shifts, which in turn are believed to have preceded the speciation of many phytophagous insects. Key words: coevolution; Filipendula ulmaria; Galerucella tenella; herbivore; host shift; resistance; Rubus arcticus; Skeppsvik Archipelago, Sweden.
- Published
- 2008
14. Differential Expression of Immune Genes between Two Closely Related Beetle Species with Different Immunocompetence following Attack by Asecodes parvidava
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Yang, Xuyue, Fors, Lisa, Slotte, Tanja, Theopold, Ulrich, Binzer-Panchal, Mahesh, Wheat, Christopher W., and Hamback, Peter A.
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insect immunity ,Genetics ,Genetik ,parasitoid wasp ,Galerucella ,transcriptome ,Zoology ,Zoologi ,hematopoiesis - Abstract
Endoparasitoid wasps are important natural enemies of many insect species and are major selective forces on the host immune system. Despite increased interest in insect antiparasitoid immunity, there is sparse information on the evolutionary dynamics of biological pathways and gene regulation involved in host immune defense outside Drosophila species. We de novo assembled transcriptomes from two beetle species and used time-course differential expression analysis to investigate gene expression differences in closely related species Galerucella pusilla and G. calmariensis that are, respectively, resistant and susceptible against parasitoid infection by Asecodes paividava parasitoids. Approximately 271 million and 224 million paired-ended reads were assembled and filtered to form 52,563 and 59,781 transcripts for G. pusilla and G. calmariensis, respectively. In the whole-transcriptome level, an enrichment of functional categories related to energy production, biosynthetic process, and metabolic process was exhibited in both species. The main difference between species appears to be immune response and wound healing process mounted by G. pusilla larvae. Using reciprocal BLAST against the Drosophila melanogaster proteome, 120 and 121 immune-related genes were identified in G. pusilla and G. calmariensis, respectively. More immune genes were differentially expressed in G. pusilla than in G. calmariensis, in particular genes involved in signaling, hematopoiesis, and melanization. In contrast, only one gene was differentially expressed in G. calmariensis. Our study characterizes important genes and pathways involved in different immune functions after parasitoid infection and supports the role of signaling and hematopoiesis genes as key players in host immunity in Galerucella against parasitoid wasps.
- Published
- 2020
15. Pre-dispersal seed predation: the role of fruit abortion and selective oviposition
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Ostergard, Hannah, Hamback, Peter A., and Ehrlen, Johan
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Beetles -- Environmental aspects ,Lathyrus -- Properties ,Plant defenses -- Evaluation ,Insect-plant relationships -- Research ,Oviposition -- Observations ,Biological sciences ,Environmental issues - Abstract
Oviposition sites of phytophagous insects should correlate with plant traits that maximize survival of the progeny. Plants, on the other hand, should benefit from traits and developmental patterns that complicate oviposition decisions. In the antagonistic interaction between plant and pre-dispersal seed predator the time lag between egg laying and seed development may allow for abortion of fruits in plants, potentially reducing fitness loss through predation. We studied the perennial herb Lathyrus vernus and the beetle pre-dispersal seed predator Bruchus atomarius in Sweden to determine the fitness consequences of nonrandom fruit abortion in the plant and oviposition patterns of the beetle. The beetle had a sophisticated ability to locate fruits with high probability of retention, partly by fruit position and phenology but also by some additional unidentified cue. Mortality of eggs was density dependent, but still the egg-laying pattern was clumped. We found no defensive strategy in the plant; instead the predictable fruit abortion pattern was associated with decreased plant fitness. We discuss how interactions may pose simultaneous selection pressures on plant and insect traits and how life history traits and other selective forces may shape the adaptive outcome of the interaction in plant and insect, respectively. Key words: Bruchus atomarius; fruit abortion; herbivore offense; Lathyrus vernus; oviposition; plantanimal interactions; plant defense.
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- 2007
16. Top-down and bottom-up effects on the spatiotemporal dynamics of cereal aphids: testing scaling theory for local density
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Hamback, Peter A., Vogt, Majbritt, Tscharntke, Teja, Thies, Carsten, and Englund, Goran
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Cereal products industry -- Analysis ,Environmental issues - Abstract
To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.2007.0030-1299.15800.x Byline: Peter A. Hamback, Majbritt Vogt, Teja Tscharntke, Carsten Thies, Goran Englund Abstract: The relationship between density and area depends on local growth rates and the area-dependence of migration rates. These rates vary among taxa due to dispersal behaviour, plot productivity and natural enemy impact. Previous studies in aphids suggest that aphid densities are highest in patches of intermediate sizes, and lower in small and large patches. The suggested mechanism causing these patterns is that the dispersal behaviour in aphids creates a mixture of area- and perimeter-dependent migration rates. In this paper, we used these predictions to examine the additional consequences of nutrient availability and natural enemies on the density-area relationship. The derived predictions were compared to data from a system with three aphid species, a set of aphid parasitoids and generalist natural enemies, and at two levels of plant nutrient availability. We find that predictions from the model based only on dispersal and local growth agree with the temporal dynamics of density-area relationships for aphids in high nutrient patches. In patches with low nutrients, high parasitism rates appeared to cause a negative density-area relationship for aphids, thereby deviating from predictions driven by the aphids' dispersal behavior. Hence, the dispersal model with scale-dependent migration rates can provide a useful tool for understanding insect distribution in patch size gradients, but the relative importance of top-down effects can completely change with plot productivity. Article History: Manuscript Accepted 16 July 2007 Article note: P. A. Hamback (peter.hamback@botan.su.se), Dept of Botany, Stockholm Univ., SE-106 91 Stockholm, Sweden. - M. Vogt, T. Tscharntke and C. Thies, Agroecology, Univ. of Gottingen, Waldweg 26, DE-370 73 Gottingen, Germany. - G. Englund, Dept of Ecology and Environmental Science, Umea Univ., SE-901 87 Umea, Sweden.
- Published
- 2007
17. Habitat specialization, body size, and family identity explain lepidopteran density--area relationships in a cross-continental comparison
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Hamback, Peter A., Summerville, Keith S., Steffan-Dewenter, Ingolf, Krauss, Jochen, Englund, Goran, and Crist, Thomas O.
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Lepidoptera -- Physiological aspects ,Lepidoptera -- Behavior ,Habitat partitioning (Biology) -- Influence ,Animal ecology -- Properties ,Population density -- Observations ,Science and technology - Abstract
Habitat fragmentation may strongly affect species density, species interactions, and the rate of ecosystem processes. It is therefore important to understand the observed variability among species responses to fragmentation and the underlying mechanisms. In this study, we compare density--area relationships (DARs) for 344 lepidopteran species belonging to 22 families (butterflies and moths). This analysis suggested that the [DAR.sub.slope] is generally positive for moths and negative for butterflies. The differences are suggested to occur because moths are largely olfactory searchers, whereas most butterflies are visual searchers. The analysis also suggests that DARs vary as a function of habitat specialization and body size. In butterflies, generalist species had a more negative [DAR.sub.slope] than specialist species because of a lower patch size threshold. In moths, the differences in [DAR.sub.slope] between forest and open habitat species were large for small species but absent for large species. This difference is argued to occur because the DARslope in large species mainly reflects their search mode, which does not necessarily vary between moth groups, whereas the slope in small species reflects population growth rates. butterflies and moths | habitat fragmentation | Lepidoptera | life history traits | olfactory and visual information
- Published
- 2007
18. Community heterogeneity and the evolution of interactions between plants and insect herbivores
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Agrawal, Anurag A., Lau, Jennifer A., and Hamback, Peter A.
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Insect-plant relationships -- Research ,Plant communities -- Research - Published
- 2006
19. Predators indirectly protect tundra plants by reducing herbivore abundance
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Hamback, Peter A., Oksanen, Lauri, Ekerholm, Per, Lindgren, Asa, Okasanen, Tarja, and Schneider, Michael
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Endangered species -- Research ,Tundra ecology -- Research ,Predatory animals -- Research ,Environmental issues - Abstract
Vole densities, plant damage and plant cover were examined in areas with or without small mammal predators to examine the potential of trophic cascades in a shrubby tundra ecosystem. Three out of five dwarf shrub species was substantially reduced on predator-free islands, providing evidence for strong cascading effects in a rather large-scale terrestrial system.
- Published
- 2004
20. Scale dependence of emigration rates
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Englund, Goran and Hamback, Peter A.
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Biological sciences ,Environmental issues - Abstract
In this paper, we examine how per capita emigration rates vary with patch size. Analyses of analytic diffusion models and lattice simulations show that the scale dependence of emigration rates is expected to differ between small and large patches. In large patches, per capita emigration rate (E) is given by E = k[A.sup.-[beta]]. A is the area, k is a constant, and [beta], which describes the strength of the scale dependence, is given by [beta] = 1 -d/2, where d is the fractal dimension of the patch boundary. In small patches, the scale dependence is predicted to level off, and the value of the scaling coefficient ([beta]) is influenced by details about how movement behaviors and mortality rates vary across patch boundaries. However, much of this variation can be explained as effects on the magnitude of per capita emigration rates. Analyses of published empirical studies of the scale dependence of emigration in terrestrial insects show that observed scaling coefficients are within the expected range (0 < [beta] < 0.5), and that scaling coefficients decrease with decreasing scale. Moreover, we find that the fractal dimension of patch boundaries and the magnitude of emigration explain much of the observed variation between different patch networks, species, years, and sexes. Key words: emigration; extinction risk; insects; meta-analysis; metapopulation models; patch networks; patch size; scale dependence.
- Published
- 2004
21. Estimating the consequences of apparent competition: a method for host-parasitoid interactions
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Hamback, Peter A. and Bjorkman, Christer
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Competition (Biology) -- Research ,Host-parasite relationships -- Research ,Insect pests -- Biological control ,Biological sciences ,Environmental issues - Abstract
To evaluate the role of natural enemies for the coexistence of competing species, it is necessary to estimate quantitatively the way in which the selectivity of the natural enemies changes the strength of competition between the competitors. This paper presents one method for doing this in host-parasitoid systems with discrete generations. The method is illustrated by analyzing the interaction between variegated leafhoppers (Erythroneura variabilis) and grape leafhoppers (E. elegantula) feeding on domestic grapes. The analysis confirms earlier observations that the recent replacement of grape leafhoppers with variegated leafhoppers is likely to be a consequence of the shared egg parasitoid Anagrus epos. Finally, we argue that the method can provide a tool to evaluate the potential of biological control measures involving alternative prey, e.g., in intercropping systems. Key words: Anagrus epos; apparent competition; biological control; competitive displacement; Erythroneura; host-parasitoid model; leafhoppers.
- Published
- 2002
22. Trophic Cascades in Terrestrial Systems: A Review of the Effects of Carnivore Removals on Plants
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Schmitz, Oswald J., Hamback, Peter A., and Beckerman, Andrew P.
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Botany -- Environmental aspects ,Carnivora -- Environmental aspects ,Meta-analysis -- Usage ,Food chains (Ecology) -- Research ,Biological sciences ,Earth sciences - Published
- 2000
23. Including Spatial Heterogeneity and Animal Dispersal When Evaluating Hunting: a Model Analysis and an Empirical Assessment in an Amazonian Community
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Siren, Anders, Hamback, Peter, and Machoa, Jose
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Spatial analysis (Statistics) -- Methods ,Spatial analysis (Statistics) -- Models ,Hunting -- Environmental aspects ,Game protection -- Research ,Game protection -- Environmental aspects ,Game protection -- Planning ,Company business planning ,Environmental issues ,Zoology and wildlife conservation - Abstract
A spatially explicit model is presented for assessing the degree of overharvesting among 12 game species in Ecuador. Findings are presented, and the role of the model in determining no-take areas and the development of sustainable hunting policies is discussed.
- Published
- 2004
24. Scale-dependence of movement rates in stream invertebrates
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Englund, Goran and Hamback, Peter A.
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Invertebrates -- Study and teaching ,Invertebrates -- Behavior ,Invertebrates -- Environmental aspects ,Animal migration -- Study and teaching ,Environmental issues - Abstract
The study of the scale-dependence of migration rates in stream invertebrates is conducted with the use of analytical models and random walk simulations in a one-dimensional habitat. Results reveal that the models and the published data on drift distances can be used to effectively calculate the expected scale-dependence of per capita emigration rates, under a wide range of environmental conditions.
- Published
- 2004
25. Herbivory and plant resource competition: a review of two interacting interactions
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Hamback, Peter A. and Beckerman, Andrew P.
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Herbivores -- Behavior ,Plant communities -- Study and teaching ,Growth (Plants) -- Analysis ,Environmental issues - Abstract
The prevalence and potential for interactive effects between herbivory and competition on plant growth and biomass is discussed. The mismatch between the spatial scale of herbivore behavior and the spatial heterogeneity of the plant community that give rise to interactive effects is examined.
- Published
- 2003
26. Chemical communication and host search in Galerucella leaf beetles
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Fors, Lisa, Liblikas, Ilme, Andersson, Petter, Borg-Karlson, Anna-Karin, Cabezas, Nancy, Mozuraitis, Raimondas, Hamback, Peter A., Fors, Lisa, Liblikas, Ilme, Andersson, Petter, Borg-Karlson, Anna-Karin, Cabezas, Nancy, Mozuraitis, Raimondas, and Hamback, Peter A.
- Abstract
Herbivore insects use a variety of search cues during host finding and mate recognition, including visual, gustatory, and olfactory stimuli, leaving multiple traits for evolution to act upon. However, information about differences or similarities in search pattern amongst closely related insect herbivore species is still scarce. Here, we study the production of and the response to pheromone in Galerucella (Coleoptera: Chrysomelidae) to investigate the beetles' search behaviour. Males of G. pusilla and G. calmariensis, two closely related species, are known to produce the aggregation pheromone dimethylfuran-lactone when feeding on their host plant, whereas no pheromones have been identified in other Galerucella species. We show that dimethylfuran-lactone is produced also by males of G. tenella, a species phylogenetically close to G. pusilla and G. calmariensis, whereas the more distantly related species G. lineola and G. sagittariae were not found to produce the same compound. To investigate the beetles' behavioural response to dimethylfuran-lactone, the pheromone was synthesized using a partly novel method and tested in olfactometers, showing that G. pusilla, G. calmariensis, and G. tenella were all attracted to the pheromone, whereas G. lineola and G. sagittariae did not respond. This suggests that the production of and the response to pheromone could be linked to the phylogenetic relatedness between the species., QC 20150227
- Published
- 2015
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27. Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services
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Elmhagen, Bodil, Destouni, Georgia, Angerbjorn, Anders, Borgström, Sara, Boyd, Emily, Cousins, Sara A. O., Dalén, Love, Ehrlen, Johan, Ermold, Matti, Hamback, Peter A., Hedlund, Johanna, Hylander, Kristoffer, Jaramillo, Fernando, Lagerholm, Vendela K., Lyon, Steve W., Moor, Helen, Nykvist, Bjorn, Pasanen-Mortensen, Marianne, Plue, Jan, Prieto, Carmen, van der Velde, Ype, Lindborg, Regina, Elmhagen, Bodil, Destouni, Georgia, Angerbjorn, Anders, Borgström, Sara, Boyd, Emily, Cousins, Sara A. O., Dalén, Love, Ehrlen, Johan, Ermold, Matti, Hamback, Peter A., Hedlund, Johanna, Hylander, Kristoffer, Jaramillo, Fernando, Lagerholm, Vendela K., Lyon, Steve W., Moor, Helen, Nykvist, Bjorn, Pasanen-Mortensen, Marianne, Plue, Jan, Prieto, Carmen, van der Velde, Ype, and Lindborg, Regina
- Abstract
Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6°C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts., QC 20161212
- Published
- 2015
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28. Exposing the structure of an Arctic food web
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University of Helsinki, Department of Agricultural Sciences, Wirta, Helena K., Vesterinen, Eero J., Hamback, Peter A., Weingartner, Elisabeth, Rasmussen, Claus, Reneerkens, Jeroen, Schmidt, Niels M., Gilg, Olivier, Roslin, Tomas, University of Helsinki, Department of Agricultural Sciences, Wirta, Helena K., Vesterinen, Eero J., Hamback, Peter A., Weingartner, Elisabeth, Rasmussen, Claus, Reneerkens, Jeroen, Schmidt, Niels M., Gilg, Olivier, and Roslin, Tomas
- Abstract
How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator-prey interactions to considering the full set of interacting species.
- Published
- 2015
29. Bayesian species delimitation reveals generalist and specialist parasitic wasps on Galerucella beetles (Chrysomelidae) : sorting by herbivore or plant host
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Hamback, Peter A., Weingartner, Elisabet, Ericson, Lars, Fors, Lisa, Cassel-Lundhagen, Anna, Stenberg, Johan A., Bergsten, Johannes, Hamback, Peter A., Weingartner, Elisabet, Ericson, Lars, Fors, Lisa, Cassel-Lundhagen, Anna, Stenberg, Johan A., and Bergsten, Johannes
- Abstract
Background: To understand the ecological and evolutionary consequences of species interactions in food webs necessitates that interactions are properly identified. Genetic analyses suggest that many supposedly generalist parasitoid species should rather be defined as multiple species with a more narrow diet, reducing the probability that such species may mediate indirect interactions such as apparent competition among hosts. Recent studies showed that the parasitoid Asecodes lucens mediate apparent competition between two hosts, Galerucella tenella and G. calmariensis, affecting both interaction strengths and evolutionary feedbacks. The same parasitoid was also recorded from other species in the genus Galerucella, suggesting that similar indirect effects may also occur for other species pairs. Methods: To explore the possibility of such interactions, we sequenced mitochondrial and nuclear genetic markers to resolve the phylogeny of both host and parasitoid and to test the number of parasitoid species involved. We thus collected 139 Galerucella larvae from 8 host plant species and sequenced 31 adult beetle and 108 parasitoid individuals. Results: The analysis of the Galerucella data, that also included sequences from previous studies, verified the five species previously documented as reciprocally monophyletic, but the Bayesian species delimitation for A. lucens suggested 3-4 cryptic taxa with a more specialised host use than previously suggested. The gene data analyzed under the multispecies coalescent model allowed us to reconstruct the species tree phylogeny for both host and parasitoid and we found a fully congruent coevolutionary pattern suggesting that parasitoid speciation followed upon host speciation. Conclusion: Using multilocus sequence data in a Bayesian species delimitation analysis we propose that hymenopteran parasitoids of the genus Asecodes that infest Galerucella larvae constitute at least three species with narrow diet breath. The evolution of para
- Published
- 2013
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30. Linking Land and Sea : Different Pathways for Marine Subsidies
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Mellbrand, Kajsa, Lavery, Paul S., Hyndes, Glenn, Hamback, Peter A., Mellbrand, Kajsa, Lavery, Paul S., Hyndes, Glenn, and Hamback, Peter A.
- Abstract
Nutrients and energy derived from marine autotrophs subsidize shore ecosystems, increasing productivity and affecting food web dynamics and structure. In this study we examined how the inland reach of such inflow effects depends on vectors carrying the marine inflow inland and on landscape structure. We used stable isotopes of carbon and nitrogen to examine the roles of arthropod vectors in carrying marine-derived nutrients inland in two very different shore ecosystems: shore meadows in Sweden with marine inflows of algae and emerging chironomid midges; and sandy beaches and shore dunes in south-western Australia with marine inflows of algae and seagrass. In a colonization experiment, we found that deposited wrack on the beach is quickly colonized by both grazers and predators. However, in both systems we found a larger inland reach of the marine subsidy than could be accounted for by deposited macrophytes on shores alone, and that dipterans and spiders potentially functioned as vectors for the inflow. Our results indicate that marine inflows are important for near-shore terrestrial ecosystems well above the water's edge, and that this effect is largely due to arthropod vectors (mainly dipterans and spiders) in both low-productivity sandy beach ecosystems at the Indian Ocean coast of Australia, and more productive shore meadows on the Baltic Sea coast of Sweden. Our findings also suggest that the type of vector transporting marine material inland may be as important as the productivity contrast between ecosystems for explaining the degree of marine influence on the terrestrial system., authorCount :4
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- 2011
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31. Patch size effects are more important than genetic diversity for plant-herbivore interactions in Brassica crops
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Hamback, Peter A., Björkman, Maria, Hopkins, Richard J., Hamback, Peter A., Björkman, Maria, and Hopkins, Richard J.
- Abstract
2. This paper examines the effect of intraspecific genetic diversity within Brassica fields on two Brassica specialists, cabbage root fly, and diamondback moth, and on a parasitoid attacking diamondback moths. Genetic diversity was manipulated both in a replacement and an additive design. 3. Both herbivore densities and parasitism rates were higher in smaller plots, with limited responses to increased within-plot diversity. All species showed variable densities across genotypes, and preference hierarchies were species specific. 4. Responses to plot size in root flies scaled with the diameter-to-area ratio, suggesting that patch detectability affected local density, whereas responses by diamondback moths and parasitoids deviated from this ratio. These species differences could be traced to differences in the residence time within patches, where diamondback moths typically spend longer and more variable time periods in patches than root flies. 5. The lack of response to genetic diversity by both herbivores suggests that egg-laying rates are affected by decisions on the plant and not by attraction from a distance, neither to the plant itself nor the patch. Patterns of differential attack may then be due to different acceptability for studied genotypes. 6. Future theories on insect responses to spatial heterogeneity should focus on species traits and how traits interact with information landscapes in the field., authorCount :3
- Published
- 2010
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32. Edge or dispersal effects - Their relative importance on arthropod densities on small islands
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Östman, Örjan, Mellbrand, Kajsa, Hamback, Peter A., Östman, Örjan, Mellbrand, Kajsa, and Hamback, Peter A.
- Abstract
Dispersal behaviour and edge effects are two potential factors determining population densities, and both effects are likely to vary with patch size. However, the relative importance of these two effects may be hard to separate because they may produce similar patterns. Here, we separate these two effects on population densities of seven groups of arthropods on small islands. To separate dispersal behaviour and edge effects, we use the fact that the slope of the density-area relationships (DAR-slope) should change with the absolute rates of dispersal, as would occur in response to island isolation, whereas the edge effect is expected not to be dependent on island isolation. For lycosid spiders, parasitic wasps and possibly herbivorous Homoptera DAR-slopes changed between isolated and non-isolated islands, suggesting dispersal behaviour to be relatively more important for explaining variation in their densities. Other arthropods (ants and Collembola), typically those with a predicted low dispersal among islands, showed similar DAR-slopes between isolated and non-isolated islands consistent with dominant edge effects. For two groups (web spiders and Diptera) the results were inconclusive. We conclude that both migratory processes and edge effects should be considered in the evaluation of patch size and isolation on density-area relationships. (C) 2008 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.
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- 2009
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33. Distance Friction and the Cost of Hunting in Tropical Forests
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Sirén, Anders H., primary, Cárdenas, Juan-Camilo, additional, Hamback, Peter, additional, and Parvinen, Kalle, additional
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- 2012
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34. Population Fluctuations of Voles in North Fennoscandian Tundra: Contrasting Dynamics in Adjacent Areas with Different Habitat Composition
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Oksanen, Tarja, primary, Schneider, Michael, additional, Rammul, Ullar, additional, Hamback, Peter, additional, and Aunapuu, Maano, additional
- Published
- 1999
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35. Seasonality, optimal foraging, and prey coexistence
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Hamback, Peter A.
- Subjects
Competition (Biology) -- Research ,Food supply -- Seasonal variations ,Herbivores -- Behavior ,Biological sciences ,Earth sciences - Published
- 1998
36. Mechanisms of Apparent Competition in Seasonal Environments: An Example with Vole Herbivory
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Hambäck, Peter A., primary, Ekerholm, Per, additional, and Hamback, Peter A., additional
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- 1997
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37. Distance Friction and the Cost of Hunting in Tropical Forest
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Sirén, Anders H., Cárdenas, Juan Camilo., Hamback, Peter., and Parvinen, Kalle.
- Abstract
Abstract:Empirical studies of tropical forest hunting have shown the existence of marked spatial gradients of hunting effort, game harvest, and animal abundance, as hunters mostly hunt near villages, roads, and rivers. The mechanisms underlying these patterns have, however, hitherto been poorly known. This article presents a spatial bioeconomic model based on the concept of distance friction, that is, an increasing marginal cost of distance. The model is validated by comparison with an economic field experiment with Amazonian hunters and with previous empirical data on hunting. (JEL Q57)
- Published
- 2013
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