| 1. |
- Norman, Sven, 1984-
(författare)
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Lake bathymetry as driver of salmonid population size structure and biomass
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most fish species undergo ontogenetic niche shifts from feeding on pelagic zooplankton, to larger benthic invertebrates and in some cases also to fish. These ontogenetic niche shifts have strong impact on the interactions within and between species, with effects on individual growth, population abundance and food web dynamics. The productivity of northern lakes is mainly controlled by light-limited primary production in benthic habitats, highlighting the importance of lake bathymetry for the abundance of benthic algae feeding macroinvertebrates, which is an important resource for fish. Theory predicts that variation in fish size structure and biomass can arise due to size-dependent differences in competitive abilities between juvenile and adults in each of their niches and by variation in niche- and habitat-specific resource production i.e. pelagic zooplankton and benthic macroinvertebrates.In this thesis, using gradient studies in mountain lakes, I studied how habitat-specific production and lake bathymetry variation affect growth, size structure and biomass in Arctic char and brown trout populations. Results showed that lake bathymetry determine the benthic contribution to whole lake primary production and the degree of ontogenetic niche shift from zooplankton to macroinvertebrates. In correspondence with theory, production of Arctic char and brown trout were related to stage- and habitat-specific gross primary production (GPP) as an increased benthic contribution to whole lake GPP in general increased individual size, population production and biomasses. Lake bathymetry also influenced the niche shift to piscivory in brown trout as reliance on piscivory were higher in relatively deep lakes more dominated by Arctic char. Finally, in a model approach, responses to different size selective harvest regulations showed that the size structure of Arctic char were more sensitive to fishing in shallow than in deep lakes. Size regulations protecting both smaller and the largest adults were shown to best preserve size structure, especially in shallower lakes. Collectively, these results contribute to the understanding of how variation in productivity and availability of stage- and habitat-specific resources and the presence of ontogenetic niche shifts affect the growth, size structure and biomass of fish. Specifically, the results highlighted the importance of shallow benthic habitats for individual size and biomass of salmonids in mountain lakes and suggests that management strategies based on relationships between lake bathymetry and population size structure and biomass could be a simple approach for sustainable management of lake salmonid population.
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| 2. |
- Perrin, Sam Wenaas, et al.
(författare)
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Integrating dispersal along freshwater ecosystems into species distribution models
- 2020
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Ingår i: Diversity & distributions. - : John Wiley & Sons. - 1366-9516 .- 1472-4642. ; 26:11, s. 1598-1611
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Our ability to model species distributions and abundances is a valuable ecological tool in predicting future distributions of species. Effectively incorporating connectivity into these predictions is crucial; however, many connectivity measures utilize metrics which may not have a direct relation to the dispersal capacity of the species they are attempting to model. The identification of more relevant metrics is therefore a vital step forward in species distribution modelling.Location: 85 freshwater lakes across a latitudinal gradient in Sweden, and an additional 282 freshwater lakes in one drainage basin in northern Norway.Methods: To investigate the effect of different connectivity measures, we first record recolonization of fish into lakes previously treated with the piscicide rotenone. Two invasive fish species, the northern pike (Esox lucius) and the European perch (Perca fluviatilis), were used as focal study species. We model the distributions of these species in a drainage basin with snapshot data of present-day distributions to see how well the effects of the different connectivity measures correspond to the effects seen in our recolonization study. Connectivity is quantified using slope and distance along streams connecting lacustrine populations.Results: The effects of connectivity variables were similar in both the recolonization study and the species distribution modelling. Incorporation of connectivity improved species distribution models significantly. There was little evidence for the inclusion of distance between populations, while there was strong evidence for the inclusion of different slope parameters for both species.Main conclusions: Our study demonstrates the need to ensure the relevance of connectivity measures when accounting for dispersal limitation in distribution models. The correspondence of estimated connectivity measures from recolonization studies to those estimated from species distribution models demonstrates a link between species dispersal capacity and the connectivity measures employed, and is likely to improve our ability to predict species future distributions.
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| 3. |
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| 4. |
- Persson, Lennart, et al.
(författare)
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Density-dependent interactions in an Arctic char - brown trout system : competition, predation, or both?
- 2013
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 70:4, s. 610-616
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Tidskriftsartikel (refereegranskat)abstract
- In the study of mechanisms structuring fish communities, mixed competition-predation interactions where large predators feed on prey fish versus those in which small predators compete with prey fish for a shared prey have been the focus of substantial research. We used a long-term data set from a system inhabited by brown trout (Salmo trutta) (predator) and Arctic char (Salvelinus alpinus) (prey) to evaluate whether mixed interspecific interactions were present in this system as suggested in other studies focusing on this species pair. We found no evidence for a negative interspecific density dependence in individual performance in either Arctic char or brown trout. In contrast, a negative intraspecific density dependence was present, especially in Arctic char. Furthermore, large brown trout condition showed a positive response to encounter rate with Arctic char (related to the density of small Arctic char). The most parsimonious interaction module to explain the Arctic char - brown trout interaction patterns in the studied system does therefore not need to include interspecific competition. We suggest that size-structured mixed competition-predation interactions in different systems are realized as being either mainly structured through interspecific predation or by competition depending on species life history characteristics and environmental conditions.
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| 5. |
- Skulason, Skuli, et al.
(författare)
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A way forward with eco evo devo : an extended theory of resource polymorphism with postglacial fishes as model systems
- 2019
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Ingår i: Biological Reviews. - : John Wiley & Sons. - 1464-7931 .- 1469-185X. ; 94:5, s. 1786-1808
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Forskningsöversikt (refereegranskat)abstract
- A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge.
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| 6. |
- Thibert-Plante, Xavier, 1980-, et al.
(författare)
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Using mathematical modelling to investigate the adaptive divergence of whitefish in Fennoscandia
- 2020
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Modern speciation theory has greatly benefited from a variety of simple mathematical models focusing on the conditions and patterns of speciation and diversification in the presence of gene flow. Unfortunately the application of general theoretical concepts and tools to specific ecological systems remains a challenge. Here we apply modeling tools to better understand adaptive divergence of whitefish during the postglacial period in lakes of northern Fennoscandia. These lakes harbor up to three different morphs associated with the three major lake habitats: littoral, pelagic, and profundal. Using large-scale individual-based simulations, we aim to identify factors required for in situ emergence of the pelagic and profundal morphs in lakes initially colonized by the littoral morph. The importance of some of the factors we identify and study - sufficiently large levels of initial genetic variation, size- and habitat-specific mating, sufficiently large carrying capacity of the new niche - is already well recognized. In addition, our model also points to two other factors that have been largely disregarded in theoretical studies: fitness-dependent dispersal and strong predation in the ancestral niche coupled with the lack of it in the new niche(s). We use our theoretical results to speculate about the process of diversification of whitefish in Fennoscandia and to identify potentially profitable directions for future empirical research.
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