| 1. |
- Sernland, Emma
(författare)
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Optimal strategies and information in foraging theory
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I present both theoretical and empirical work where we have studied how humans and animals use information in situations where they need to continually update their information on the density of a resource. We have found that the amount of information, and the way the information is presented, are important factors for how well decisions are adapted to current circumstances. In an empirical study on humans, we found that humans seem to have a default idea of the distribution of a resource. This default idea seems to be plastic, i.e. it is adjusted according to incoming information. The way additional information was presented, as well as the information content, was important for how well the default idea was adjusted to current circumstances.By using mathematical models, we have also studied whether access to information from group members, so called public information, is one of the reasons why some species live in groups. When group members aim to maximize its intake rate of food and share both information and food items found equally, and when each individual has to pay all the cost for travelling between foraging patches, the intake rate of food will decrease with increasing group size. The animals will spend a larger proportion of the time on travelling between patches and less time on foraging the larger the group size. In this case, information sharing on food density in patches is not a reason why animals live in groups.We have also used mathematical models to study the information dynamics in a group of foraging animals that cannot both search for food and information at the same time. The animals aim to maximize their survival, and are given three behavioural choices in each time step: stay and search for food, stay and scan for information, or leave the current patch. The results show that the choice of behaviour depends on the energy reserves of the individual. An animal with low energy reserves searches for food and leaves the patch if its assessment of potential patch quality decreases to a certain level. An animal with high energy reserves chooses to stay in the patch and scan for information. In our model we assume that when one individual leaves the patch, the rest of the group also leaves. This means that it is those individuals that have low energy reserves that will make the leaving decisions for the group.In the end, we use these theories on Bayesian foraging, information updating and decision-making in order to develop a new type of effort-based quota for sustainable fisheries management: an effort-based dynamic quota (EDQ). We show that by using information from ongoing fishing combined with fishing data from earlier years, we can reach a higher maximum sustainable yield compared to using a total allowable catch (TAC).
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| 2. |
- Koch, Kamilla, et al.
(författare)
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Morphological differences in the ovary of Libellulidae (Odonata)
- 2009
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Ingår i: International Journal of Odonatology. - Oxford : Taylor & Francis. - 1388-7890 .- 2159-6719. ; 12:1, s. 147-156
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Tidskriftsartikel (refereegranskat)abstract
- All female Odonata have been assumed to produce oocytes continuously during their mature life span. However, a recent study of ovariole orientation and development led to the suggestion that Libellulidae are divided into two groups of species, one with continuous, the other with stepwise oocyte production. To find more evidence of this division, we compared the size variation and growth within the vitellarium of the ovary, studying oocytes, and follicle cells. We found that morphological characters discriminate between the two ovary types in eight of the 10 investigated species. In both types we found an increase in all measurements from the anterior to the posterior end of the vitellarium. The increase in oocyte width and follicle cell length was significantly higher in species with a continuous oocyte production. We also noted that follicle cells may have more than one nucleus and that their number can vary during vitellogenesis. Our study confirmed the hypotheses that two different ovary types exist in Libellulidae. The two species not fitting into this grouping could be an artefact of small samp le size due to intraspecific phenotypic plasticity, or else there might be more than two ovary groups, or even a continuum. We could not offer an explanation as to how the process of stepwise oocyte production differs from continuous based production on morphological characters.
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| 3. |
- Norrström, Niclas
(författare)
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Artificial neural networks in models of specialization and sympatric speciation
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with specialization and how it is linked to sympatric speciation. The trait driving specialization is a cue recognition trait modelled with artificial neural networks that exploiters use to discriminate beneficial resources from detrimental resources based on the signals of the resources. Paper I investigates how haploid exploiters and the resources coevolve when the signals of the resources can evolve through mutations. We find that this coevolution can be a cyclic process with saltational changes between different stages and that evolution is only directional and the exploiters are only specialists in parts of this cycle. In simulations underlying Paper II the signals of the resources can not mutate but the exploiters have a diploid genome and the organisms reproduce sexually. We show that the disruptive selection stemming from exploiters specializing on different resources can overcome the homogenizing effect of sexual recombination when exploiters mate randomly and produce a functional genetic polymorphism with specialized exploiters. A functional genetic polymorphism removes the force of reinforcement but we run simulations where the exploiters have a mating gene determining if mating is random or if exploiters should mate assortatively in Paper III. We find that assortative invades the exploiter population and homozygote specialists evolve because the genetic polymorphism pays a cost by having some alleles being silenced (that is they do not contribute to the complete phenotype) in certain genotypes so a mutation in these silenced alleles is not selected against, which cause these alleles to accumulate deleterious mutations. The homozygote specialists, mating assortatively, are much more efficiently removing deleterious mutations from the population and hence can invade the population. Finally, in Paper IV we investigate the effects of resource and resource signal arrangements in the environment. We show that the environment can influence the evolution of specialization and sympatric speciation. By modelling a resource discrimination trait based on the interaction of epistatic genes we find a novel force promoting sympatric speciation over genetic polymorphisms.
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| 4. |
- Schneider, Nicole, et al.
(författare)
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Influence and value of different water regimes on avian species richness in arid inland Australia
- 2009
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Ingår i: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 18:2, s. 457-471
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Tidskriftsartikel (refereegranskat)abstract
- Riparian habitats in arid landscapes are recognised for their structurally diverse vegetation and diverse bird species assemblages. In the extensive semi-arid and arid centre of Australia, riparian woodland habitats are impacted by pastoral land-use which may negatively influence vegetation structure and avian species composition. However, pastoralism has promoted the establishment of artificial water bodies, so that additional riparian vegetation may occur in the landscape. In this study, we surveyed the importance of different water regimes (i.e. artificial lakes, natural waterholes, desert sites) together with their associated vegetation on avian species richness in north-western New South Wales, Australia. Our results show that bird species richness was highest at water locations, in particular at artificial lakes. Avian species richness was negatively associated with distance to water bodies, both in desert vegetation types and in the riparian vegetation type along dry creeks. Moreover, riparian habitats supported larger avian assemblages and especially those of sedentary bird species compared to the surrounding shrub-steppe landscape. This indicates that artificial water bodies may be of significance for arid zone bird species and might gain in importance with changing water availabilities due to climatic changes.
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| 5. |
- Hallenberg, Nils, 1947, et al.
(författare)
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Pseudolagarobasidium (Basidiomycota): on the reinstatement of a genus of parasitic, saprophytic, and endophytic resupinate fungi
- 2008
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Ingår i: Botany. - 1916-2804. ; 86:11, s. 1319-1325
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Tidskriftsartikel (refereegranskat)abstract
- The small resupinate genus Pseudolagarobasidium (Polyporales, Basidiomycota) presently comprises less than five species, all of which were described from tropical to subtropical regions, and two of which are root parasites on leguminous trees. The genus has recently been synonymized with Radulodon on morphological grounds, and the present study evaluates this proposal in a molecular context. Pseudolagarobasidium was found to constitute a well supported, monophyletic group excluding Radulodon and this synonymy is rejected. The ecological range of the genus spans saprotrophy to parasitism, and this study presents evidence that at least one lineage in Pseudolagarobasidium is endophytic in the cacao tree (Theobroma cacao L.). Key words: Polyporales, Radulodon, phylogeny, plant interactions. Résumé: Le Pseudolagarobasidium (Polyporales, Basidiomycota) constitue un genre de petits champignons résupinés qui comporte actuellement cinq espèces, toutes décrites à partir de régions tropicales ou subtropicales, incluant deux espèces parasites des racines d'arbres de la famille des légumineuses. On en a récemment établi la synonymie avec le genre Radulodon sur la base morphologique, mais les auteurs utilisent ici l'approche moléculaire. On constate que le genre Pseudolagarobasidium constitue un groupe monophylétique robuste excluant les Radulodon ce qui conduit au rejet de cette synonymie. L'amplitude écologique du genre va du saprophytisme au parasitisme, et on présente des preuves qu'au moins une lignée est un endophyte du cacaoyer (Theobroma cacao L.). Mots-clés : Polyporales, Radulon, phylogénie, interactions végétales.
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| 6. |
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| 7. |
- Anderbrant, Olle, et al.
(författare)
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Release of sex pheromone and its precursors in the pine sawfly Diprion pini (Hym., Diprionidae)
- 2005
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Ingår i: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 15:3, s. 147-151
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Tidskriftsartikel (refereegranskat)abstract
- The first identification of a sex pheromone of a pine sawfly (Hymenoptera, Diprionidae) dates back almost thirty years. Since then, female-produced pheromones of over twenty diprionid species have been investigated by solvent extraction followed by separation and identification. However, no study has shown what the females actually release. Collection of airborne compounds using absorbtion on charcoal filter as well as solid phase microextraction (SPME) followed by analysis employing gas chromatography combined with mass spectrometry (GC-MS), revealed an unusual system in Diprion pini, in which the pheromone precursor alcohol, 3,7-dimethyl-2-tridecanol, is released together with acetic, propionic, butyric and isobutyric acids. The corresponding acetate, propionate and butyrate esters of 3,7-dimethyl-2-tridecanol were also found in the samples. All esters were electrophysiologically active, and the propionate and isobutyrate were attractive in trapping experiments. Based on these and earlier reported results, it seems that at least in part of its range, the pheromone response of D. pini is not very specific with regard to the functional group, as long as this is an ester.
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| 8. |
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| 9. |
- Lesch, Christine, et al.
(författare)
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A role for Hemolectin in coagulation and immunity in Drosophila melanogaster
- 2007
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Ingår i: Developmental and Comparative Immunology. - : Elsevier BV. - 0145-305X .- 1879-0089. ; 31:12, s. 1255-1263
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Tidskriftsartikel (refereegranskat)abstract
- Hemolectin has been identified as a candidate clotting factor in Drosophila. We reassessed the domain structure of Hemolectin (Hml) and propose that instead of C-type lectin domains, the two discoidin domains are most likely responsible for the protein's lectin activity. We also tested Hml's role in coagulation and immunity in Drosophila. Here we describe the isolation of a new hml allele in a forward screen for coagulation mutants, and our characterization of this and two other hml alleles, one of which is a functional null. While loss of Hml had strong effects on larval hemolymph coagulation ex vivo, mutant larvae survived wounding. Drosophila thus possesses redundant hemostatic mechanisms. We also found that loss of Hml in immune-handicapped adults rendered them more sensitive to Gram(-) bacteria infection. This demonstrates an immunological role of this clotting protein and reinforces the importance of the clot in insect immunity.
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| 10. |
- Bergsten, Anna
(författare)
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Population Differentiation in Solidago virgaurea along Altitudinal Gradients
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Altitudinal gradients offer attractive opportunities for studies of population differentiation in response to environmental heterogeneity. In this thesis, I examined population differentiation along altitudinal gradients by combining common-garden experiments with field studies and experiments in alpine, subalpine and boreal populations of the perennial herb Solidago virgaurea. More specifically, I determined whether leaf physiology in terms of nitrogen concentration and resorption, flowering phenology, flower production and reproductive effort vary along altitudinal gradients. Nitrogen concentration in green leaves were higher in alpine than in subalpine and boreal populations. These differences persisted when plants were grown from seeds in a common-garden experiment at two sites, suggesting that the differences have a genetic component. There was mixed support for a trade-off between maximized carbon gain through the maintenance of high nitrogen concentration, and minimized nitrogen loss through high resorption. In their natural habitats alpine populations began flowering later than subalpine populations, but this difference was reversed when plants were grown in a common environment. This suggests that genetic differences among populations counteract environmental effects and reduce phenotypic variation in flowering time among populations. Flowering time thus shows countergradient genetic variation in S. virgaurea. In a common-garden experiment, boreal populations produced more flowers and had a higher reproductive effort than subalpine and alpine populations indicating habitat-specific genetic differences in reproductive allocation. In a field study, which included three populations, seed set was close to zero in the alpine population, intermediate in the subalpine population, and high in the boreal population. Experimental flower removal showed that seed production was associated with a considerable cost in terms of reduced flowering propensity the following year, but did not support the hypothesis that a large floral display is important for pollination success.
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