| 1. |
- Sernland, Emma
(författare)
-
Optimal strategies and information in foraging theory
- 2005
-
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).
|
|
| 2. |
- Larsson, Kjell, 1958-, et al.
(författare)
-
Population differentiation in the redshank (Tringa totanus) as revealed by mitochondrial DNA and amplified fragment length polymorphism markers
- 2005
-
Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 6:3, s. 321-331
-
Tidskriftsartikel (refereegranskat)abstract
- The redshank (Tringa totanus) is declining throughout Europe and to implement efficient conservation measures, it is important to obtain information about the population genetic structure. The aim of the present study was two-fold. First, we analysed the genetic variation within and between populations in the Baltic region in southern Scandinavia. Evidence of genetic structure would suggest that different populations might require separate management strategies. Second, in an attempt to study large-scale genetic structure we compared the Baltic populations with redshanks from northern Scandinavia and Iceland. This analysis could reveal insights into phylogeography and long-term population history. DNA samples were collected from six breeding sites in Scandinavia presumed to include two subspecies (totanus and britannica) and a further sample from Iceland (subspecies robusta). Two methods were used to study the population genetic structure. Domain II and III of the mitochondrial control region was analysed by DNA sequencing and nuclear DNA was analysed by screening amplified fragment length polymorphism (AFLP) markers. Mitochondrial DNA showed no variation between individuals in domain II. When analysing an 481 bp fragment of domain III seven haplotypes were found among birds. On the basis of mtDNA sequences, redshanks showed some evidence of a recent expansion from a bottlenecked refugial population. Bayesian analyses of AFLP data revealed a significant genetic differentiation between suggested subspecies but not between populations within the Baltic region. Our results indicate that populations of redshanks in Europe constitute at least three separate management units corresponding to the recognised subspecies.
|
|
| 3. |
- Norrström, Niclas
(författare)
-
Artificial neural networks in models of specialization and sympatric speciation
- 2009
-
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.
|
|
| 4. |
- Schneider, Nicole, et al.
(författare)
-
Influence and value of different water regimes on avian species richness in arid inland Australia
- 2009
-
Ingår i: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 18:2, s. 457-471
-
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.
|
|
| 5. |
- Hallenberg, Nils, 1947, et al.
(författare)
-
Pseudolagarobasidium (Basidiomycota): on the reinstatement of a genus of parasitic, saprophytic, and endophytic resupinate fungi
- 2008
-
Ingår i: Botany. - 1916-2804. ; 86:11, s. 1319-1325
-
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.
|
|
| 6. |
- Anderbrant, Olle, et al.
(författare)
-
Release of sex pheromone and its precursors in the pine sawfly Diprion pini (Hym., Diprionidae)
- 2005
-
Ingår i: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 15:3, s. 147-151
-
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.
|
|
| 7. |
- Boström, Björn, et al.
(författare)
-
Can isotopic fractionation during respiration explain the 13C-enriched sporocarps of ectomycorrhizal and saprotrophic fungi?
- 2008
-
Ingår i: New Phytologist. - Cambridge : Cambridge University Press. - 0028-646X .- 1469-8137. ; 177:4, s. 1012-1019
-
Tidskriftsartikel (refereegranskat)abstract
- • The mechanism behind the 13C enrichment of fungi relative to plant materials is unclear and constrains the use of stable isotopes in studies of the carbon cycle in soils.• Here, we examined whether isotopic fractionation during respiration contributes to this pattern by comparing δ13C signatures of respired CO2, sporocarps and their associated plant materials, from 16 species of ectomycorrhizal or saprotrophic fungi collected in a Norway spruce forest.• The isotopic composition of respired CO2 and sporocarps was positively correlated. The differences in δ13C between CO2 and sporocarps were generally small, < ±1‰ in nine out of 16 species, and the average shift for all investigated species was 0.04‰. However, when fungal groups were analysed separately, three out of six species of ectomycorrhizal basidiomycetes respired 13C-enriched CO2 (up to 1.6‰), whereas three out of five species of polypores respired 13C-depleted CO2 (up to 1.7‰; P < 0.05). The CO2 and sporocarps were always 13C-enriched compared with wood, litter or roots.• Loss of 13C-depleted CO2 may have enriched some species in 13C. However, that the CO2 was consistently 13C-enriched compared with plant materials implies that other processes must be found to explain the consistent 13C-enrichment of fungal biomass compared with plant materials.
|
|
| 8. |
|
|
| 9. |
- Högberg, Peter, et al.
(författare)
-
Factors determining the 13C abundance of soil-respired CO2 in Boreal forests
- 2005
-
Ingår i: Stable isotopes and biosphere-atmosphere interactions. - : Elsevier. - 9780120884476 ; , s. 47-68
-
Bokkapitel (refereegranskat)abstract
- Analysis of the isotopic composition of the CO2 respired from soils may reveal information about the important component of the ecosystem C balance. This is crucial, since a large terrestrial sink for atmospheric CO2 has been located in the northern hemisphere, and the vast boreal forests may be largely responsible. At the same time, boreal and arctic ecosystems have large amounts of C stored in the soil, and could potentially become a source of CO2 in a warmer climate promoting more rapid decomposition of soil organic matter. Furthermore, the northern hemisphere has complex dynamics in terms of annual fluctuations in both the concentration of CO2 in the atmosphere and its δl3C. It is of utmost importance to understand the causes of this variability, since it interferes with the partitioning between the ocean and the terrestrial contributions in global models. This chapter aims to provide an update on the reviews by Flanagan and Ehleringer and Ehleringer et al. on the causation of the δ13C of the soil CO2 efflux and, in doing this, focuses on the boreal forests.
|
|
| 10. |
- Bourlat, Sarah, et al.
(författare)
-
Feeding ecology of Xenoturbella bocki (phylum Xenoturbellida) revealed by genetic barcoding
- 2008
-
Ingår i: Molecular Ecology Resources. - 1755-098X. ; 8, s. 18-22
-
Tidskriftsartikel (refereegranskat)abstract
- The benthic marine worm Xenoturbella is frequently contaminated with molluscan DNA, which had earlier caused confusion resulting in a suggested bivalve relationship. In order to find the source of the contaminant, we have used molluscan sequences derived from Xenoturbella and compared them to barcodes obtained from several individuals of the nonmicroscopic molluscs sharing the same environment as Xenoturbella. Using cytochrome oxidase 1, we found the contaminating sequences to be 98% similar to the bivalve Ennucula tenuis. Using the highly variable D1-D2 region of the large ribosomal subunit in Xenoturbella, we found three distinct species of contaminating molluscs, one of which is 99% similar to the bivalve Abra nitida, one of the most abundant bivalves in the Gullmarsfjord where Xenoturbella was found, and another 99% similar to the bivalve Nucula sulcata. These data clearly show that Xenoturbella only contains molluscan DNA originating from bivalves living in the same environment, refuting former hypotheses of a bivalve relationship. In addition, these data suggest that Xenoturbella feeds specifically on bivalve prey from multiple species, possibly in the form of eggs and larvae.
|
|
