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    • Article
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    Still not enough taxonomists: reply to Joppa et al.

    Bacher, Sven
    Trends in Ecology and Evolution. - 2012/27/2/65–66
    2012
    Disponible
    Plus…
    Titre: Still not enough taxonomists: reply to Joppa et al.
    Auteur: Bacher, Sven
    Date: 2012
    Publication en relation: Trends in Ecology and Evolution. - 2012/27/2/65–66
    Document hôte: Trends in Ecology and Evolution
    Identifiant: 10.1016/j.tree.2011.11.003 (DOI)

    • Article
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    Differential effects of flower feeding in an insect host–parasitoid system

    Kehrli, Patrik
    Bacher, Sven
    Basic and Applied Ecology. - 2008/9/6/709-717
    2007-10-10
    Disponible
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    Titre: Differential effects of flower feeding in an insect host–parasitoid system
    Auteur: Kehrli, Patrik
    Contributeur: Bacher, Sven
    Date: 2007-10-10
    Description: In many insect host–parasitoid systems, both the host and its parasitoids forage on shared floral resources. As a result of insect behaviour, morphology and physiology, flower species may act selectively at different levels of such systems, e.g., between the trophic levels of hosts and parasitoids, between species within a guild, between sexes or individuals within a species or between life history traits within an individual. We asked if effects of selectivity are consistent across levels in the horse chestnut leafminer, Cameraria ohridella, and its parasitoid complex. Insects were exposed singly in no-choice feeding trials to twelve common flower species and their survival and reproduction were recorded. Only one of twelve flower species (Ranunculus acris) tended to selectively favour the longevity of leafminers, but not of parasitoids. No flower species were found to favour parasitoids only. Both trophic levels profited from feeding on Anthriscus sylvestris, however, parasitoids benefited up to eight times more than their hosts. No differences were found among the species of the parasitoid guild, but females lived significantly longer than males, and single individuals within species were able to exploit generally unfavourable flower species. Out of the seven flower species that increased the longevity of leafminer females, only Chaerophyllum hirsutum significantly enhanced the number of eggs laid. Fecundity was generally positively correlated with longevity of leafminer females, but two flower species (C. hirsutum, Taraxacum officinale) had an additional positive effect on fecundity. In conclusion, we demonstrated that flowers act differently on life history traits in a host–parasitoid system at a multitude of biological levels and that these effects are not always consistent across levels. Selective plant-derived resources can therefore modify herbivore–natural enemy interactions in ways that are more complex than currently appreciated.
    Publication en relation: Basic and Applied Ecology. - 2008/9/6/709-717
    Document hôte: Basic and Applied Ecology
    Identifiant: 10.1016/j.baae.2007.07.001 (DOI)

    • Article
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    Higher establishment success in specialized parasitoids: support for the existence of trade-offs in the evolution of specialization

    Rossinelli, Silvia
    Bacher, Sven
    Functional Ecology. - 2015/29/2/277–284
    2015-02-01
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    Titre: Higher establishment success in specialized parasitoids: support for the existence of trade-offs in the evolution of specialization
    Auteur: Rossinelli, Silvia
    Contributeur: Bacher, Sven
    Date: 2015-02-01
    Description: Most animals do not feed on all the resources available to them, but the mechanisms behind the evolution of dietary specialization are still debated. A central but unanswered question is whether specialists generally gain fitness advantages on their resource compared to generalists, experiencing a trade-off between the ability to use a broad range of resources and the fitness reached on each single one.Empirical tests so far suffered from difficulties in measuring fitness; they were restricted to few species, and results were equivocal. This lack of support for the importance of trade-offs gave rise to theories explaining the evolution of specialization without such trade-offs.Using a large dataset of intentional biological control introductions of 254 species of parasitoids from 15 families to locations outside their native range, we show that establishment success, a measure of total fitness, is higher in specialized species. This result holds when controlling for possible confounding factors such as the number of introduced individuals (propagule pressure).The outcome of this study provides robust evidence that dietary specialization implies fitness advantages in an entire species-rich taxon, indicating that trade-offs might be widely involved in the evolution of specialization.
    Publication en relation: Functional Ecology. - 2015/29/2/277–284
    Document hôte: Functional Ecology
    Identifiant: 10.1111/1365-2435.12323 (DOI)

    • Plusieurs versions

    Still not enough taxonomists: reply to Joppa et al

    Bacher, Sven
    Trends in Ecology & Evolution, 2012, Vol.27(2), pp.65-66 [Revue évaluée par les pairs]

    • Plusieurs versions

    Ökologie kompakt

    Nentwig, Wolfgang
    • Article
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    Impact of flower-dwelling crab spiders on plant-pollinator mutualisms

    Brechbühl, Rolf
    Kropf, Christian, Bacher, Sven
    Basic and Applied Ecology. - 2009///10.1016/j.baae.2009.07.001
    2009-08-24
    Disponible
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    Titre: Impact of flower-dwelling crab spiders on plant-pollinator mutualisms
    Auteur: Brechbühl, Rolf
    Contributeur: Kropf, Christian; Bacher, Sven
    Date: 2009-08-24
    Sujet: Indirect effects - Multitrophic interactions - Plant fitness - Predation - Xysticus
    Description: Indirekte Effekte entstehen, wenn eine Art eine Dritte beeinflusst, indem sie das Verhalten einer zweiten Art modifiziert. Es wird vermutet, dass Bestäuber Pflanzen, auf denen Krabbenspinnen (Thomisidae) jagen, meiden und dass sich dies auf die Fitness der Pflanzen niederschlagen könnte, da diese weniger besucht würden. Allerdings ist bisher nicht bekannt, wie verschiedene Bestäubergruppen auf Spinnen reagieren und wann eine Fitnessreduktion der Pflanzen zu erwarten ist. Die Reaktion von Bestäubern auf (1) getrocknete Spinnen, (2) künstliche Papierspinnen und (3) Blüten ohne Spinnen (Kontrolle) wurde auf zwei verschiedenen Blütenarten mit Hilfe von kontinuierlicher Videoüberwachung untersucht. Die Resultate zeigen, dass die Bestäuber auf der einen Pflanzenart (Anthemis tinctoria) die getrockneten Spinnen mieden. Die Bestäuber zeigten keine signifikante Meidung bezüglich der Papierspinnen. Hummeln und Bienen reagierten nicht negativ auf die Spinnen, während solitäre Bienen und Schwebfliegen die Blüten mit getrockneten Spinnen stark mieden. Einen Einfluss auf die Fitness der Blüten hatte dies allerdings nicht, und es konnte kein Unterschied in der Anzahl gekeimter Samen zwischen Blüten mit getrockneten Spinnen und den Kontrollblüten festgestellt werden. Wir stellen die Hypothese auf, dass “top-down”-Effekte auf Pflanzen durch Prädation auf Bestäuber vom Ausmass der Spezialisierung der einzelnen Bestäubergruppen und deren Tendenz Spinnen zu meiden, abhängen dürften.
    Indirect effects in interactions occur when a species influences a third species by modifying the behaviour of a second one. It has been suggested that indirect effects of crab spiders (Thomisidae) on pollinator behaviour can cascade down the food web and negatively affect plant fitness. However, it is poorly understood how different pollinator groups react to crab spiders and, thus, when a reduction in plant fitness is likely to occur. Using continuous video surveillance, we recorded the behaviour of pollinators on two flower species and the pollinators’ responses to three crab spider treatments: inflorescences (1) with a pinned dried spider, (2) with a spider model made of paper, and (3) without spiders (control). We found that pollinators avoided inflorescences with dried spiders only on one plant species (Anthemis tinctoria). Pollinators showed no significant avoidance of paper spiders. Honeybees and bumblebees did not react to dried spiders, but solitary bees and syrphid flies showed a strong avoidance. Finally, we found no evidence that inflorescences with dried spiders suffered from a decrease in fitness in terms of a reduced seed set. We hypothesise that top-down effects of predators on plants via pollinators depend on the degree of specialisation of pollinators and their tendency to avoid spiders.
    Publication en relation: Basic and Applied Ecology. - 2009///10.1016/j.baae.2009.07.001
    Document hôte: Basic and Applied Ecology
    Identifiant: 10.1016/j.baae.2009.07.001 (DOI)

    • Article
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    Gaps in border controls are related to quarantine alien insect invasions in Europe

    Bacon, Steven James
    Bacher, Sven, Aebi, Alexandre
    PLoS One. - 2012/7/10/e47689
    2012-10-12
    Disponible
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    Titre: Gaps in border controls are related to quarantine alien insect invasions in Europe
    Auteur: Bacon, Steven James
    Contributeur: Bacher, Sven; Aebi, Alexandre
    Date: 2012-10-12
    Description: Alien insects are increasingly being dispersed around the world through international trade, causing a multitude of negative environmental impacts and billions of dollars in economic losses annually. Border controls form the last line of defense against invasions, whereby inspectors aim to intercept and stop consignments that are contaminated with harmful alien insects. In Europe, member states depend on one another to prevent insect introductions by operating a first point of entry rule – controlling goods only when they initially enter the continent. However, ensuring consistency between border control points is difficult because there exists no optimal inspection strategy. For the first time, we developed a method to quantify the volume of agricultural trade that should be inspected for quarantine insects at border control points in Europe, based on global agricultural trade of over 100 million distinct origin-commodity-species-destination pathways. This metric was then used to evaluate the performance of existing border controls, as measured by border interception results in Europe between 2003 and 2007. Alarmingly, we found significant gaps between the trade pathways that should be inspected and actual number of interceptions. Moreover, many of the most likely introduction pathways yielded none or very few insect interceptions, because regular interceptions are only made on only a narrow range of pathways. European countries with gaps in border controls have been invaded by higher numbers of quarantine alien insect species, indicating the importance of proper inspections to prevent insect invasions. Equipped with an optimal inspection strategy based on the underlying risks of trade, authorities globally will be able to implement more effective and consistent border controls.
    Publication en relation: PLoS One. - 2012/7/10/e47689
    Document hôte: PLoS One
    Identifiant: 10.1371/journal.pone.0047689 (DOI)

    • Article
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    Bottom-Up and top-down effects influence Bruchid beetle individual performance but not population densities in the field

    Zaugg, Isabelle
    Benrey, Betty, Bacher, Sven
    PLoS ONE. - 2013/8/1/e55317
    2013-01-29
    Disponible
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    Titre: Bottom-Up and top-down effects influence Bruchid beetle individual performance but not population densities in the field
    Auteur: Zaugg, Isabelle
    Contributeur: Benrey, Betty; Bacher, Sven
    Date: 2013-01-29
    Description: Plant quality (bottom-up) and natural enemies (top-down) can influence the individual performance of herbivorous insects on their host plants, but few studies measured at the same time the influence on population densities in the field. We investigated if plant quality of different wild common bean populations, Phaseolus vulgaris L. (Fabaceae), affects the performance of the bean weevil, Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae), and one of its enemies, the ectoparasitoid Dinarmus basalis (Rondani) (Hymenoptera: Pteromalidae), in controlled laboratory experiments. Additionally, we examined if parasitoids influence the beetles' development and if increased individual beetle and parasitoid fitness lead to higher field population densities. We show that bean quality and parasitoids affected individual bean weevil performance under laboratory and field conditions. In the presence of parasitoids, fewer and smaller beetles emerged. However, beetle and parasitoid performance were not correlated. Increased individual performance was not leading to higher population densities; we found no correlations between measured performance components and beetle field infestation levels or parasitism rates. We conclude that bottom-up or top-down effects measured at the individual level do not always translate into population effects; therefore it is important to discriminate between effects acting on individual insects and those acting on populations.
    Publication en relation: PLoS ONE. - 2013/8/1/e55317
    Document hôte: PLoS ONE
    Identifiant: 10.1371/journal.pone.0055317 (DOI)

    • Article
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    What determines the impact of alien birds and mammals in Europe?

    Kumschick, Sabrina
    Bacher, Sven, Blackburn, Tim M
    Biological Invasions. - 2012///-
    2012-09-28
    Disponible
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    Titre: What determines the impact of alien birds and mammals in Europe?
    Auteur: Kumschick, Sabrina
    Contributeur: Bacher, Sven; Blackburn, Tim M
    Date: 2012-09-28
    Sujet: Bird - Clutch size - Diet breadth - Exotic - Habitat breadth - Invasion - Litter size - Mammal - Species traits
    Description: An often-cited reason for studying the process of invasion by alien species is that the understanding sought can be used to mitigate the impacts of the invaders. Here, we present an analysis of the correlates of local impacts of established alien bird and mammal species in Europe, using a recently described metric to quantify impact. Large-bodied, habitat generalist bird and mammal species that are widespread in their native range, have the greatest impacts in their alien European ranges, supporting our hypothesis that surrogates for the breadth and the amount of resources a species uses are good indicators of its impact. However, not all surrogates are equally suitable. Impacts are generally greater for mammal species giving birth to larger litters, but in contrast are greater for bird species laying smaller clutches. There is no effect of diet breadth on impacts in birds or mammals. On average, mammals have higher impacts than birds. However, the relationships between impact and several traits show common slopes for birds and mammals, and relationships between impact and body mass and latitude do not differ between birds and mammals. These results may help to anticipate which species would have large impacts if introduced, and so direct efforts to prevent such introductions.
    Publication en relation: Biological Invasions. - 2012///-
    Document hôte: Biological Invasions
    Identifiant: 10.1007/s10530-012-0326-6 (DOI)

    • Article
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    Assessing the socio-economic impacts of priority marine invasive fishes in the Mediterranean with the newly proposed SEICAT methodology

    Galanidi, Marika
    Zenetos, Argyro, Bacher, Sven
    Mediterranean Marine Science. - 2018/19/1/107–123
    2018-05-23
    Disponible
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    Titre: Assessing the socio-economic impacts of priority marine invasive fishes in the Mediterranean with the newly proposed SEICAT methodology
    Auteur: Galanidi, Marika
    Contributeur: Zenetos, Argyro; Bacher, Sven
    Date: 2018-05-23
    Description: The assessment of impacts of alien species is one of the most critical steps for the prioritisation of policy and management actions and this requires assessment schemes that can compare impacts across different taxa, ecosystems and socio- economic contexts. The Environmental and Socio-Economic Impact Classification of Alien Species (EICAT and SEICAT) are two methodologies that facilitate such comparisons. They classify alien taxa along a 5-level, semi-quantitative scale based on the magnitude of their impacts on the environment and human well-being, respectively. In this study, we applied both protocols to seven invasive marine fishes that that are already considered “high-risk” and have been singled out for monitoring in relation to fisheries in the Mediterranean (Plotosus lineatus, Pterois miles/volitans, Fistularia commersonii, Lagocephalus sceleratus, Siganus rivulatus/Siganus luridus and Saurida lessepsianus). Here, we focus in particular on their socio-economic impacts. By systematically reviewing the published literature and scoring the demonstrated impacts we show that the taxa with the highest environmental impacts (Major) are P. miles/volitans and the two siganids. In contrast, L. sceleratus had the highest socio-economic impact (Moderate) and highest number of impact records. The high and uniform densities of P. lineatus caused widespread, albeit less severe, impacts in the invaded areas. Human activities that are primarily affected by the selected taxa are commercial and recreational fishing and other recreational uses of the sea through impacts on, mainly, material assets and human health. We found significant data gaps regarding the species’ environmental impacts, especially relating to predation, and make specific recommendations for future research. The links between environmental and socio-economic impacts, especially their cultural dimensions, are poorly documented and require novel approaches. Surveys specifically adapted to capture the distinction between socio-economic impact classes would strengthen our confidence in the assessments and better inform prioritisation and decision-making.
    Publication en relation: Mediterranean Marine Science. - 2018/19/1/107–123
    Document hôte: Mediterranean Marine Science
    Identifiant: 10.12681/mms.15940 (DOI)