431 resultados para HERBIVORE DETERRENCE
Resumo:
Human-caused environmental changes are creating regional combinations of environmental conditions that, within the next 50 to 100 years, may fall outside the envelope within which many of the terrestrial plants of a region evolved. These environmental modifications might become a greater cause of global species extinction than direct habitat destruction. The environmental constraints undergoing human modification include levels of soil nitrogen, phosphorus, calcium and pH, atmospheric CO2, herbivore, pathogen, and predator densities, disturbance regimes, and climate. Extinction would occur because the physiologies, morphologies, and life histories of plants limit each species to being a superior competitor for a particular combination of environmental constraints. Changes in these constraints would favor a few species that would competitively displace many other species from a region. In the long-term, the “weedy” taxa that became the dominants of the novel conditions imposed by global change should become the progenitors of a series of new species that are progressively less weedy and better adapted to the new conditions. The relative importance of evolutionary versus community ecology responses to global environmental change would depend on the extent of regional and local recruitment limitation, and on whether the suite of human-imposed constraints were novel just regionally or on continental or global scales.
Resumo:
The activation of plant defensive genes in leaves of tomato plants in response to herbivore damage or mechanical wounding is mediated by a mobile 18-amino acid polypeptide signal called systemin. Systemin is derived from a larger, 200-amino acid precursor called prosystemin, similar to polypeptide hormones and soluble growth factors in animals. Systemin activates a lipid-based signaling cascade, also analogous to signaling systems found in animals. In plants, linolenic acid is released from membranes and is converted to the oxylipins phytodienoic acid and jasmonic acid through the octadecanoid pathway. Plant oxylipins are structural analogs of animal prostaglandins which are derived from arachidonic acid in response to various signals, including polypeptide factors. Constitutive overexpression of the prosystemin gene in transgenic tomato plants resulted in the overproduction of prosystemin and the abnormal release of systemin, conferring a constitutive overproduction of several systemic wound-response proteins (SWRPs). The data indicate that systemin is a master signal for defense against attacking herbivores. The same defensive proteins induced by wounding are synthesized in response to oligosaccharide elicitors that are generated in leaf cells in response to pathogen attacks. Inhibitors of the octadecanoid pathway, and a mutation that interrupts this pathway, block the induction of SWRPs by wounding, systemin, and oligosaccharide elicitors, indicating that the octadecanoid pathway is essential for the activation of defense genes by all of these signals. The tomato mutant line that is functionally deficient in the octadecanoid pathway is highly susceptible to attacks by Manduca sexta larvae. The similarities between the defense signaling pathway in tomato leaves and those of the defense signaling pathways of macrophages and mast cells of animals suggests that both the plant and animal pathways may have evolved from a common ancestral origin.
Resumo:
Although the prevalence or even occurrence of insect herbivory during the Late Carboniferous (Pennsylvanian) has been questioned, we present the earliest-known ecologic evidence showing that by Late Pennsylvanian times (302 million years ago) a larva of the Holometabola was galling the internal tissue of Psaronius tree-fern fronds. Several diagnostic cellular and histological features of these petiole galls have been preserved in exquisite detail, including an excavated axial lumen filled with fecal pellets and comminuted frass, plant-produced response tissue surrounding the lumen, and specificity by the larval herbivore for a particular host species and tissue type. Whereas most suggestions over-whelmingly support the evolution of such intimate and reciprocal plant-insect interactions 175 million years later, we provide documentation that before the demise of Pennsylvanian age coal-swamp forests, a highly stereotyped life cycle was already established between an insect that was consuming internal plant tissue and a vascular plant host responding to that herbivory. This and related discoveries of insect herbivore consumption of Psaronius tissues indicate that modern-style herbivores were established in Late Pennsylvanian coal-swamp forests.
Resumo:
Parasitic and predatory arthropods often prevent plants from being severely damaged by killing herbivores as they feed on the plants. Recent studies show that a variety of plants, when injured by herbivores, emit chemical signals that guide natural enemies to the herbivores. It is unlikely that herbivore-damaged plants initiate the production of chemicals solely to attract parasitoids and predators. The signaling role probably evolved secondarily from plant responses that produce toxins and deterrents against herbivores and antibiotics against pathogens. To effectively function as signals for natural enemies, the emitted volatiles should be clearly distinguishable from background odors, specific for prey or host species that feed on the plant, and emitted at times when the natural enemies forage. Our studies on the phenomena of herbivore-induced emissions of volatiles in corn and cotton plants and studies conducted by others indicate that (i) the clarity of the volatile signals is high, as they are unique for herbivore damage, produced in relatively large amounts, and easily distinguishable from background odors; (ii) specificity is limited when different herbivores feed on the same plant species but high as far as odors emitted by different plant species and genotypes are concerned; (iii) the signals are timed so that they are mainly released during the daytime, when natural enemies tend to forage, and they wane slowly after herbivory stops.
Resumo:
Delaware sets the governance standards for most public companies. The ability to attract corporations could not be explained solely by the existence of a favorable statutory regime. Delaware was not invariably the first or the only state to implement management friendly provisions. Given the interpretive gaps in the statute and the critical importance of the common law in the governance process, courts played an outsized role in setting legal standards. The management friendly nature of the Delaware courts contributed significantly to the state’s attraction to public corporations. A current example of a management friendly trend in the case law had seen the recent decisions setting out the board’s authority to adopt bylaws under Section 109 of the Delaware General Corporation Law (DGCL), particularly those involving the shifting of fees in litigation against the corporation or its directors. The DGCL allows bylaws that address “the business of the corporation, the conduct of its affairs, and its rights or powers or the rights or powers of its stockholders, directors, officers or employees.” The broad parameters are, however, subject to limits. Bylaws cannot be inconsistent with the certificate of incorporation or “the law.” Law includes the common law. The Delaware courts have used the limitations imposed by “the law” to severely restrict the reach of shareholder inspired bylaws. The courts have not used the same principles to impose similar restraints on bylaws adopted by the board of directors. This can be seen with respect to bylaws that restrict or even eliminate the right of shareholders to bring actions against management and the corporation. In ATP Tour, Inc. v. Deutscher Tennis Bund the court approved a fee shifting bylaw that had littl relationship to the internal affairs of the corporation. The decision upheld the bylaw as facially valid.The decision ignored a number of obvious legal infirmities. Among other things, the decision did not adequately address the requirement in Section 109(b) that bylaws be consistent with “the law.” The decision obliquely acknowledged that the provisions would “by their nature, deter litigation” but otherwise made no effort to assess the impact of this deterrence on shareholders causes of action. The provision in fact had the practical effect of restricting, if not eliminating, litigation rights granted by the DGCL and the common law. Perhaps most significantly, however, the bylaws significantly limited common law rights of shareholders to bring actions against the corporation and the board. Given the high dismissal rates for these actions, fee shifting bylaws imposed a meaningful risk of liability on plaintiffs. Moreover, because judgments in derivative suits were paid to the corporation, shareholders serving as plaintiffs confronted the risk of liability without any offsetting direct benefit. By preventing suits in this area, the bylaw effectively insulated the behavior of boards from legal challenge. The ATP decision was poorly reasoned and overstepped acceptable boundaries. The management friendly decision threatened the preeminent role of Delaware in the development of corporate law. The decision raised the specter of federal intervention and the potential for meaningful competition from the states. Because the opinion examined the bylaw in the context of non-stock companies, the reasoning may remain applicable only to those entities and never make the leap to for-profit stock corporations. Nonetheless, the analysis reflects a management friendly approach that does not adequately take into account the impact of the provision on the rights of shareholders.
Resumo:
A major problem related to the treatment of ecosystems is that they have no available mathematical formalization. This implies that many of their properties are not presented as short, rigorous modalities, but rather as long expressions which, from a biological standpoint, totally capture the significance of the property, but which have the disadvantage of not being sufficiently manageable, from a mathematical standpoint. The interpretation of ecosystems through networks allows us to employ the concepts of coverage and invariance alongside other related concepts. The latter will allow us to present the two most important relations in an ecosystem – predator–prey and competition – in a different way. Biological control, defined as “the use of living organisms, their resources or their products to prevent or reduce loss or damage caused by pests”, is now considered the environmentally safest and most economically advantageous method of pest control (van Lenteren, 2011). A guild includes all those organisms that share a common food resource (Polis et al., 1989), which in the context of biological control means all the natural enemies of a given pest. There are several types of intraguild interactions, but the one that has received most research attention is intraguild predation, which occurs when two organisms share the same prey while at the same time participating in some kind of trophic interaction. However, this is not the only intraguild relationship possible, and studies are now being conducted on others, such as oviposition deterrence. In this article, we apply the developed concepts of structural functions, coverage, invariant sets, etc. (Lloret et al., 1998, Esteve and Lloret, 2006a, Esteve and Lloret, 2006b and Esteve and Lloret, 2007) to a tritrophic system that includes aphids, one of the most damaging pests and a current bottleneck for the success of biological control in Mediterranean greenhouses.
Resumo:
The issue: Anti-cartel enforcement is the least controversial of competition policy themes. Agreements to restrict competition such as price fixing or market sharing have obvious negative effects on welfare. Within the European Union, however, industry representatives have increasingly voiced concern that the European Commission applies a too-strict fining policy to enforce anti-cartel law, particularly since the introduction of new guidelines on fines in 2006. Fines are said to be too high, disproportionate and liable to introduce distortions into the market, ultimately leading to higher prices for consumers. It is often argued that more lenient approaches should be followed in crisis times. Policy challenge: High fines for cartel activity could entail costs for society and might be difficult to implement. Nevertheless, there is no case for reducing current levels of EU anti-cartel fines. Fine levels already take the economic crisis into account, and the net present value of fines might prove to be too low to discourage collusion. We estimate that fines might even be not high enough to offset the additional profits yielded by collusion. Fines should be complemented with other measures to increase deterrence, in particular personal sanctions targeting company officers who are responsible for leading the company to commit infringements. In the short term, pressure on decision makers could be increased by reducing the expected duration of investigations.
Resumo:
The March 2014 European Council could enter the history books as a turning point, not only in the EU’s relations with Russia but also in its role as a foreign policy actor. Events in Ukraine inevitably dominated the Summit, with EU leaders adopting a balanced approach aimed at achieving three key objectives – de-escalation, containment/deterrence and cooperation – based on political and economic support for Ukraine, increased but limited pressure on Russia, and moves to strengthen ties with other EU neighbours. The Summit also discussed a range of economic and environmental policy issues, with the situation in Ukraine casting a long shadow over the discussion on energy policy, but failed to reach agreement on the EU’s climate goals to 2030, or to put more flesh on the bones of calls for a European “industrial renaissance”. However, two other developments were particularly significant: the creation of the second pillar of the future banking union, establishing a single regime for winding down failing banks; and changes to the savings tax directive, bringing years of negotiation to an end.
Resumo:
Norway is currently the only Western European state and ‘old’ NATO member that strongly relies on the traditional dimension of NATO's collective defence. It is also the only ally in Western Europe which perceives Russia as a threat to its military security, in the so-called High North. In order to successfully deal with the potential challenges and threats in the region, Norway has been pursuing a defence policy based on cooperation and deterrence. Cooperation means improving collaboration with Russia in cross-border relations, in the petroleum sector and in the military sphere. The deterrent measures include maintaining NATO’s credibility as a collective defence alliance; increasing military cooperation with the United States; building up Norway’s own military capabilities; and developing military cooperation across Northern Europe. The primary objective of Oslo’s defence policy is to minimise the likelihood of crises and conflicts emerging in the High North which could prove too ‘big’ for Norway but too ‘small’ for NATO.
Resumo:
Many studies suggest that balanced budget rules can restrain sovereign debt and lower sovereign borrowing costs, even if those rules are never enforced in court. Typically, this is explained as a result of a legal deterrence logic, in which the threat of judicial enforcement deters sovereigns from violating the rules. By contrast, we argue that balanced budget rules work by coordinating decentralized punishment of sovereigns by bond markets, rather than by posing a credible threat of judicial enforcement. Therefore, the clarity of the focal point provided by the rule, rather than the strength of its judicial enforcement mechanisms, determines its effectiveness. We develop a formal model that captures the logic of our argument, and we assess this model using data on US states. We then consider implications of our argument for the impact of the balanced budget rules recently imposed on eurozone states in the Fiscal Compact Treaty.
Resumo:
On 28 January 2008 the European Union launched the military operation EUFOR in Chad and the Central African Republic. Its mandate was to contribute to the security of the civilian population, the numerous refugees from neighboring Darfur and the local presence of the United Nations. This paper describes and analyses the planning process of this operation at the political-strategic and military-strategic levels with the aim of understanding how the military instrument was intended to generate the desired political effects. The paper argues that, from a military perspective, the EUFOR operation is based on the concept of humanitarian deterrence: the threat of military force is used to discourage potential spoilers from targeting the civilian population. As with any military operation, the planning of EUFOR was plagued by various elements of friction. At least some of this friction seems to flow from the mismatch in expectations between the political-strategic and military-strategic levels. The various political and military-technical constraints within which the operation was planned resulted in an operational posture that is less decisive than what the political ambitions would have suggested.
Resumo:
Competition law seeks to protect competition on the market as a means of enhancing consumer welfare and of ensuring an efficient allocation of resources. In order to be successful, therefore, competition authorities should be adequately equipped and have at their disposal all necessary enforcement tools. However, at the EU level the current enforcement system of competition rules allows only for the imposition of administrative fines by the European Commission to liable undertakings. The main objectives, in turn, of an enforcement policy based on financial penalties are two fold: to impose sanctions on infringing undertakings which reflect the seriousness of the violation, and to ensure that the risk of penalties will deter both the infringing undertakings (often referred to as 'specific deterrence') and other undertakings that may be considering anti-competitive activities from engaging in them (often referred to as 'general deterrence'). In all circumstances, it is important to ensure that pecuniary sanctions imposed on infringing undertakings are proportionate and not excessive. Although pecuniary sanctions against infringing undertakings are a crucial part of the arsenal needed to deter competition law violations, they may not be sufficient. One alternative option in that regard is the strategic use of sanctions against the individuals involved in, or responsible for, the infringements. Sanctions against individuals are documented to focus the minds of directors and employees to comply with competition rules as they themselves, in addition to the undertakings in which they are employed, are at risk of infringements. Individual criminal penalties, including custodial sanctions, have been in fact adopted by almost half of the EU Member States. This is a powerful tool but is also limited in scope and hard to implement in practice mostly due to the high standards of proof required and the political consensus that needs first to be built. Administrative sanctions for individuals, on the other hand, promise to deliver up to a certain extent the same beneficial results as criminal sanctions whilst at the same time their adoption is not likely to meet strong opposition and their implementation in practice can be both efficient and effective. Directors’ disqualification, in particular, provides a strong individual incentive for each member, or prospective member, of the Board as well as other senior executives, to take compliance with competition law seriously. It is a flexible and promising tool that if added to the arsenal of the European Commission could bring balance to the current sanctioning system and that, in turn, would in all likelihood make the enforcement of EU competition rules more effective. Therefore, it is submitted that a competition law regime in order to be effective should be able to deliver policy objectives through a variety of tools, not simply by imposing significant pecuniary sanctions to infringing undertakings. It is also clear that individual sanctions, mostly of an administrative nature, are likely to play an increasingly important role as they focus the minds of those in business who might otherwise be inclined to regard infringing the law as a matter of corporate risk rather than of personal risk. At the EU level, in particular, the adoption of directors’ disqualification promises to deliver more effective compliance and greater overall economic impact.
Resumo:
CFSP's performance is widely regarded as weak. Why did Europe's stance in world politics not improve with the Treaty of Maastricht? The article analyses the present policy approach and the institutionalist and militarystrategic reform proposals. It is argued that policy and proposals suffer from drawbacks leading to an uncomprehensive formulation of a Common Foreign and Security Policy. Both do not provide CFSP with a necessary strategy but instead largely duplicate existing organizations. Furthermore, they propose concepts that are not viable because member states do not agree on a common defense policy. In addition, they fail to offer answers adequate to today's challenges, which are not primarily military in nature. Instead, a socioeconomic security policy appears to be a more realistic option. It is necessary because no other organization provides it sufficiently; it is viable because member states could agree on iti and it is adequate because the stabilization of countries in Eastern Europe is best achieved by social and economic policy-and not by military deterrence.
Resumo:
Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator--rey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.
Resumo:
Goose grazing on arctic tundra vegetation has shown both positive and negative effects on subsequent foraging conditions. To understand the potential of a density-dependent feedback on herbivore population size, the relation between grazing pressure and future foraging conditions is essential. We studied the effect of increasing grazing pressure of barnacle geese (Branta leucopsis) on Spitsbergen. During the establishment of a breeding colony in the period 1992-2004, the proportion of graminoids decreased in the diet of wild geese, while the percentage of mosses increased. Grazing trials with captive geese in an unexploited area showed a similar shift in diet composition. High-quality food plants were depleted within years and over years. Intake rate declined too and as consequence, metabolisable energy intake rate (MEIR) decreased rapidly with increasing grazing pressure. During three successive years of experimental grazing, MEIR decreased at all levels of grazing pressure and declined below minimal energetic requirements when grazing exceeded natural levels of grazing pressure. This suggests that foraging conditions rapidly decline with increasing grazing pressure in these low-productive habitats. The potential for density-dependent feedbacks on local population increase is discussed.