| 1. |
|
|
| 2. |
- 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).
|
|
| 3. |
- Gross, Elisabeth, et al.
(författare)
-
Allelochemical interactions among aquatic primary producers
- 2012. - 1
-
Ingår i: Chemical Ecology in Aquatic Systems. - Oxford : Oxford University Press. - 9780199583102 ; , s. 196-209
-
Bokkapitel (refereegranskat)abstract
- Allelopathy is the study of biochemically-driven organismic interactions among primary producers. One organism affects others by the release of allelochemicals that are transported to the target cells, and cause a negative (or positive) response. Most aquatic allelochemicals are amphiphilic, thus have a sufficient solubility in the water, and at the same time can bind to and penetrate lipophilic cell membranes. Allelopathic interactions are not static but are influenced by variable environmental stressors. Resource availability can both affect the production and release of allelochemicals by the producing organism, but also influence the susceptibility of the target cells. The biosynthesis and excretion of allelochemicals might involve costs for the producing organism, and these costs will only be balanced if a net gain, i.e. better resource availability such as space or nutrients or secondary benefits, e.g. predator deterrence, are achieved. Allelopathic effects against cooccurring organisms might lead to coevolutionary responses, i.e. a lower susceptibility of target cells or to more advanced allelochemicals. Target organisms from different habitats might be more susceptible, especially if they are not acquainted with the allelochemicals. The transfer of laboratory results on allelopathy to realistic field conditions is complex, and might in the long run benefit from advanced analytical and molecular methods identifying specific target cell responses in situ.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
-
Mikroalger : – vår tids miljöhjältar
- 2020
-
Konstnärligt arbeteabstract
- Utställningen Mikroalger - vår tids miljöhjältar visade forskningen inom projektet ALGOLAND ett projekt inom Linnéuniversitetets spetsforskning inom ekologi och evolutionsforskning. Inom Algoland undersöker forskare mikroalgers potential att rena luft och vatten som kommer från industrier. I projektet kombineras marinekologisk forskning med kompetens från industrin för att nå innovativa, hållbara lösningar som minskar utsläpp av koldioxid och närsalter. Samtidigt produceras viktiga produkter som djurfoder och biobränslen. Metoden har potential att bidra till sänkta växthusgasutsläpp i framtiden. Syftet med utställningen var att sprida kunskap om mikroalgers förmåga att rena luft och vatten samt bidra till en större medvetenhet kring vatten generellt. Målgrupper var befintliga och presumtiva studenter, anställda på Linnéuniversitetet, allmänhet samt skolbarn.
|
|
| 7. |
- Nilsson, Anna
(författare)
-
The Problem of Partial Migration - the Case of the Blue Tit
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the evolution of bird migration, partial migration is assumed to be an important intermediate step between migration and residency. Partial migration is characterised by the existence of both migratory and resident individuals in a given population. Compared to regular migration, relatively little is known about partial migrants and their migratory performances. In my thesis, I have studied the partially migratory blue tit Cyanistes caeruleus in Scandinavia. The numbers of migrating blue tits have increased during the last decades, according to systematic, long-term observations at Falsterbo, a migratory passage site in southern Sweden. Global warming and subsequent climate change predict that the proportion of resident individuals should increase in partially migratory populations. However, in relation to its breeding densities, the blue tit has maintained its migratory activity indicating that the effect of environmental factors on partial migration may be complex. Migrating blue tits differ from more regular migrants in several aspects. Compared to regular migrants, blue tits migrate relatively short distances with extraordinarily low speeds. They also have a strong response to weather en route and, in contrast to regular migrants, they are to a large extent affected by certain specific weather cues, e.g. absence of cloud cover, associated with favourable migratory conditions. Thus, partial migrants seem to choose the safest occasions for migratory flights with all orientation cues available. Partial migrants have the ability to change behavioural strategy. Young birds often switch from migration to residency with increasing age. Therefore, partial migrants need adaptations for both migration and residency. In experimental comparisons between migratory and resident blue tits, I have found differences with respect to behavioural dominance, personality and metabolic rate. Migrants were dominant under clear skies. Thus, weather conditions seem to have a surprisingly large effect on partial migrants. Furthermore, fast explorers of new environments are more often migratory. Residents, on the other hand, had higher basal metabolic rate (BMR) than migrants, probably as a consequence of harsher conditions during winter. Hence, we need to study the dual demands of migration and residency in partial migrants and the resulting trade-offs between adaptations to the two strategies to understand the evolution of migration.
|
|
| 8. |
- Rundlöf, Maj
(författare)
-
Biodiversity in Agricultural Landscapes: Landscape and Scale-Dependent Effects of Organic Farming
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Declines in the distribution and abundance of many farmland species during recent decades have been attributed to agricultural intensification. Agri-environment schemes are commonly used in Europe to reduce this loss of farmland biodiversity, but their effectiveness may depend on several external factors. In this thesis, I have used one such scheme, organic faming, as a landscape scale experiment to test if its effect on the species richness and abundance of butterflies, bumble bees and plants differs depending on the surrounding landscape context or on which spatial scale organic farming is applied. In the first studies, including pairs of organic and conventional farms located in either heterogeneous or homogeneous landscapes, I found that the species richness and abundance of both butterflies and bumble bees were enhanced by organic farming compared to conventional farming, partly related to higher abundance of flowers on organically managed farmland. However, the enhancing effect depended on the landscape context, such that the species richness and abundance were only significantly higher on organic farms in intensively farmed homogeneous landscapes, but not on the ones in less intensively farmed heterogeneous landscapes. Bumble bee species were classified into three groups based on their colony sizes, reflecting differences in their landscape perception. The abundances of bumble bees with small and large colonies were positively associated with organic farming, while the ones with medium sized colonies instead were affected by landscape heterogeneity, which may indicate differences between groups in sensitivity to resources fragmentation. For the scale-dependent effect of organic farming, I found that local butterfly and plant species richness and butterfly abundance were enhanced by organic farming at a local scale. In addition, my results showed that, besides the local effect, the amount of organic farming in the surrounding landscape can have an additive (species richness) or interactive effect (abundance). Local species richness was positively affected by a large proportion of organic farming at the landscape scale, while the local farming practice was of larger importance for local butterfly abundance in conventionally managed landscapes compared to organically managed ones. In conclusion, I show that the effectiveness of agri-environment schemes to promote biodiversity may depend on the landscape heterogeneity and on how large proportion of a landscape that are subjected to the scheme. These results consequently imply that to increase their efficiency it may be important to consider the spatial arrangement of schemes and their allocation at a landscape scale.
|
|
| 9. |
|
|
| 10. |
- Sundblad, Göran
(författare)
-
Spatial Modelling of Coastal Fish – Methods and Applications
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental factors influence species and habitats on multiple scales creating a mosaic of distribution patterns. Studying factors shaping these patterns are central to our understanding of population dynamics and ultimately ecosystem functioning. Information on the distribution of resources and conservation values are also highly needed in marine management as coastal areas are increasingly influenced by human activities. In this thesis, large-scale field data is used to explore how strong environmental gradients found on multiple scales in the coastal areas of the Baltic Sea influence fish habitats. The underlying concepts are based in the field of species distribution modelling, whereby habitat maps can be produced using environmental layers in a geographic information system. Distribution modelling is further used to address both ecological and applied questions by examining effects of habitat limitation on fish population sizes and to evaluate management actions aimed at habitat conservation. I show that specific habitat requirements for fish species of both freshwater and marine origin can be described using environmental variables and that species-environment relationships can be used to predict the distribution of early life-stages of fish in the Baltic Sea archipelagos. Further, predicted habitat availability of a specific life-stage was directly related to adult population size of Eurasian perch Perca fluviatilis, signifying that the abundance of large predatory fish can be limited by specific recruitment habitats. Lastly, by predicting the distribution of an assemblage of coastal fish species and their associated habitats, an assessment of a network of marine protected areas was performed. Results revealed large gaps in the current network and identified areas suitable for future protection. By demonstrating how current habitat protection can be improved by including critical habitats for coastal fish population sizes this thesis points to the benefits of integrating nature conservation and fisheries management. Based on these findings I conclude that species distribution modelling provides a suitable analytical framework for assessing the habitat requirements of organisms. An increased understanding of habitat-population relationships and an ability to accurately map ecologically important features will be of great value for an ecosystem-based marine management.
|
|
