| 1. |
- Janz, Niklas, et al.
(författare)
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No effect of larval experience on adult host preferences in Polygonia c-album (Lepidoptera: Nymphalidae): on the persistence of Hopkins' host selection principle
- 2009
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Ingår i: Ecological Entomology. - Oxford : Blackwell. - 0307-6946 .- 1365-2311. ; 34:1, s. 50-57
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Tidskriftsartikel (refereegranskat)abstract
- 1. The possible effect of juvenile imprinting or 'chemical legacy' on the subsequent oviposition - often called the 'Hopkins' host selection principle' - has been a controversial but recurrent theme in the literature on host-plant preference. While it appears possible in principle, experimental support for the hypothesis is equivocal. The present study points out that it is also important to consider its theoretical implications, and asks under what circumstances, if any, it should be favoured by natural selection. 2. Following this reasoning, it is predicted that host preference in the polyphagous butterfly Polygonia c-album L. (Lepidoptera, Nymphalidae) should not be influenced by larval environment. This was tested by rearing larvae on three natural host plants: the high-ranked Urtica dioica and the medium-ranked Salix cinerea and Ribes uva-crispa, and exposing the naive females to oviposition choices involving the same set of plants. 3. It was found that larval host plant had no effect on oviposition decisions of the adult female. Hence, the Hopkins' host selection principle does not seem to be applicable in this species. 4. Based on recent insights on how accuracy of environmental versus genetic information should affect the control of developmental switches, the conditions that could favour the use of juvenile cues in oviposition decisions are discussed. Although the Hopkins' host selection hypothesis cannot be completely ruled out, we argue that the circumstances required for it to be adaptive are so specific that it should not be invoked as a general hypothesis for host selection in plant-feeding insects.
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| 2. |
- Nylin, Sören, 1959-, et al.
(författare)
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Geographical variation in host plant utilization in the comma butterfly: the roles of time constraints and plant phenology
- 2009
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Ingår i: Evolutionary Ecology. - Dordrecht : Springer. - 0269-7653 .- 1573-8477. ; 23, s. 807-825
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Tidskriftsartikel (refereegranskat)abstract
- What is the role of time-constraints in determining geographical variation in the resource use of organisms? One hypothesis concerning phytophagous insects predicts a local narrowing of host plant range at localities where a short development time is important (because an additional generation per season is only just possible), with increased specialization on host plants permitting fast development. To test this hypothesis, populations of the polyphagous comma butterfly (Nymphalidae: Polygonia c-album) from five European areas (localities in Norway, Sweden, England, Belgium and Spain) were sampled and the preferences of laboratory-reared female butterflies were investigated, by a choice test between Salix caprea and the fastest host Urtica dioica. The results suggest that females of both of two northern univoltine populations (time-stressed from Norway and time-relaxed from Sweden) accept the slow host S. caprea to a higher degree than females of more southern populations with partial additional generations (time-stressed). We thus found partial support for the tested hypothesis, but also conflicting results that cast doubt on its broad generality. Moreover, a split-brood investigation on Swedish stock demonstrated that larval performance is similar on S. caprea and U. dioica early in the summer, but that later in the season S. caprea is a much inferior host. This is reflected by a seasonal trend towards specialization on U. dioica and also provides a simpler explanation than the time-constraints theory for avoidance of S. caprea (and other woody hosts) in areas with two or more generations of insects per year, illustrating the importance of plant phenology as a constraint on resource use in phytophagous insects. Absolute and relative larval performance on the two hosts varied little among populations across Europe, but lower survival on S. caprea in the populations most specialized on U. dioica and related plants may be indicative of performance trade-offs.
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| 3. |
- Söderlind, Gustaf, et al.
(författare)
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Adaptive Time-Stepping and Computational Stability
- 2006
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Ingår i: Journal of Computational and Applied Mathematics. - : Elsevier BV. - 0377-0427. ; 185, s. 225-243
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the effects of adaptive time-stepping and other algorithmic strategies on the computational stability of ODE codes. We show that carefully designed adaptive algorithms have a most significant impact on computational stability and reliability. A series of computational experiments with the standard implementation of Dassl and a modified version, including stepsize control based on digital filters, is used to demonstrate that relatively small algorithmic changes are able to extract a vastly better computational stability at no extra expense. The inherent performance and stability of Dassl are therefore much greater than the standard implementation seems to suggest.
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| 4. |
- Söderlind, Gustaf, et al.
(författare)
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Evaluating Numerical ODE/DAE Methods, Algorithms and Software
- 2006
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Ingår i: Journal of Computational and Applied Mathematics. - : Elsevier BV. - 0377-0427. ; 185:2, s. 244-260
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Tidskriftsartikel (refereegranskat)abstract
- Until recently, the testing of ODE/DAE software has been limited to simple comparisons and benchmarking. The process of developing software from a mathematically specified method is complex: it entails constructing control structures and objectives, selecting iterative methods and termination criteria, choosing norms and many more decisions. Most software constructors have taken a heuristic approach to these design choices, and as a consequence two different implementations of the same method may show significant differences in performance. Yet it is common to try to deduce from software comparisons that one method is better than another. Such conclusions are not warranted, however, unless the testing is carried out under true ceteris paribus conditions. Moreover, testing is an empirical science and as such requires a formal test protocol; without it conclusions are questionable, invalid or even false. We argue that ODE/DAE software can be constructed and analyzed by proven, ''standard'' scientific techniques instead of heuristics. The goals are computational stability, reproducibility, and improved software quality. We also focus on different error criteria and norms, and discuss modifications to Daspk and Radau5. Finally, some basic principles of a test protocol are outlined and applied to testing these codes on a variety of problems.
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| 5. |
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