| 1. |
- Anderson, Peter, et al.
(author)
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Cannibalism and intraguild predation involved in the intra- and inter-specific interactions of the invasive fall armyworm, Spodoptera frugiperda, and lepidopteran maize stemborers
- 2023
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In: Journal of Pest Science. - : Springer Science and Business Media LLC. - 1612-4758 .- 1612-4766. ; 96, s. 1455-1464
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Journal article (peer-reviewed)abstract
- Cannibalism and intraguild predation can play important roles in determining spread and survival or death of organisms which share the same resource. However, the relationship between cannibalism and intraguild predation, and the costs and benefits of such behaviours, is difficult to establish within insect communities, and little is known about how such behaviours are affected by invasive species. The present study was aimed at assessing the interactions between larvae of fall armyworm (Spodoptera frugiperda) and maize stemborers (native to Africa, Busseola fusca, and Sesamia calamistis and native to India, Chilo partellus) in relation to cannibalism and intraguild predation when they utilize the same resource. Experiments involving treatments with either single species of S. frugiperda or any of the stemborers or pairwise species combinations with S. frugiperda were conducted under laboratory conditions. The experimental insect larvae were reared on maize leaves and monitored until the last developmental stage where cannibalism and/or intraguild predation, larval survival, and relative growth rate were recorded. Results of the intraspecific interaction indicated that S. frugiperda exhibited cannibalism to a larger degree than the stemborers species, especially at the late instars. The higher cannibalism trait in S. frugiperda turned, however, to competitive advantage as it led to a higher degree of intraguild predation when they cohabit with stemborer species and allowed FAW to gain a greater relative growth rate. Overall, interactions with FAW are detrimental for stemborer species and may be an important factor to explain the invasive success of S. frugiperda. Such knowledge is essential to understand the mechanisms behind ecological interactions between pests with overlapping niches in the field and in designing successful integrated pest management strategies.
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| 2. |
- Anderson, Peter, et al.
(author)
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Does Host Size and Feeding Status Influence the Egg Load of Microplitis rufiventris (Hymenoptera: Braconidae)?
- 2011
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In: Annals of the Entomological Society of America. - 0013-8746. ; 104, s. 221-228
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Journal article (peer-reviewed)abstract
- Laboratory experiments were conducted to determine the effect of host instar and feeding status on the egg load of early life stage in Microplitis rufiventris Kokujev (Hymenoptera: Braconidae), a solitary koinobiont endoparasitoid of some noctuid pests. The wasps that developed from fourth or fifth instars of Spodoptera littoralis (Boisduval) larvae were heavier in weight than those from earlier stages. Different numbers of mature eggs were found in the two ovaries of the female wasp. Egg loads, corresponding to fitness, were significantly influenced by female weight and feeding status. However, the interactions between the two treatment factors were not significant. The average number of mature eggs carried by females at eclosion time ranged from 52 eggs in smaller wasps to 62 eggs in larger wasps. Females that were fed had higher egg loads and egg maturation rate than unfed females. However, female wasps were capable of maturing considerable number of eggs without feeding; suggesting that they produce a certain portion of eggs from nutritional reserves that had been stored during larval stage. Female wasps are weakly synovigenic, with an egg maturation at a rate of approximate to 1.8 eggs per h. Further investigation is required to verify the rate of egg maturation and eventually egg resorption in different stages of adult female M. rufiventris.
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| 3. |
- Kettis, Magdalena, 1964-
(author)
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The Challenge of Political Risk : Exploring the political risk management of Swedsih multinational corporations
- 2004
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Doctoral thesis (other academic/artistic)abstract
- In an overarching aim to bridge the gap between political science and international business studies, this study explores how, against the backgrond of globalization, multinational coprorations understand and deal with the influence of many differet and sometimes very dynamic political environments, by focusing on the political risk management of a number of Swedish multinational corporations invoved in foreign investing. Based on interviewswith coproate executives in these corporations, this qualitative study found that Swedish invetsors use a "pragmatic" approach toeards political risk and the political envrionments in which they operate. The study also drwas attention to teh role of multinational corporations in teh formation of politica risk as teh result of corporate politiacl activity and the possibility that multinational corporations are moving towards a more pronounced political role.It is suggetsed that political risk needs to be considered not only in terms of the potential impact of the political environment on firms, but also in terms of teh impact of teh firm on the environment, as the political environment cannot be taken as a given, but is the outcome of a process that involves adaption to the environment as well as attempts to change that environment.
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