| 1. |
- Berggren, Hanna, et al.
(author)
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Effects of environmental translocation and host characteristics on skin microbiomes of sun-basking fish
- 2023
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In: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society. - 0962-8452 .- 1471-2954. ; 290:2013
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Journal article (peer-reviewed)abstract
- Variation in the composition of skin-associated microbiomes has been attributed to host species, geographical location and habitat, but the role of intraspecific phenotypic variation among host individuals remains elusive. We explored if and how host environment and different phenotypic traits were associated with microbiome composition. We conducted repeated sampling of dorsal and ventral skin microbiomes of carp individuals (Cyprinus carpio) before and after translocation from laboratory conditions to a semi-natural environment. Both alpha and beta diversity of skin-associated microbiomes increased substantially within and among individuals following translocation, particularly on dorsal body sites. The variation in microbiome composition among hosts was significantly associated with body site, sun-basking, habitat switch and growth, but not temperature gain while basking, sex, personality nor colour morph. We suggest that the overall increase in the alpha and beta diversity estimates among hosts were induced by individuals expressing greater variation in behaviours and thus exposure to potential colonizers in the pond environment compared with the laboratory. Our results exemplify how biological diversity at one level of organization (phenotypic variation among and within fish host individuals) together with the external environment impacts biological diversity at a higher hierarchical level of organization (richness and composition of fish-associated microbial communities).
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| 2. |
- Berggren, Hanna, et al.
(author)
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Testing for local adaptation to spawning habitat in sympatric subpopulations of northern pike by reciprocal translocation of embryos
- 2016
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:5
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Journal article (peer-reviewed)abstract
- We tested for local adaption in early life-history traits by performing a reciprocal translocation experiment with approximately 2500 embryos of pike (Esox lucius) divided in paired split-family batches. The experiment indicated local adaptation in one of the two subpopulations manifested as enhanced hatching success of eggs in the native habitat, both when compared to siblings transferred to a non-native habitat, and when compared to immigrant genotypes from the other subpopulation. Gene-by-environment effects on viability of eggs and larvae were evident in both subpopulations, showing that there existed genetic variation allowing for evolutionary responses to divergent selection, and indicating a capacity for plastic responses to environmental change. Next, we tested for differences in female life-history traits. Results uncovered that females from one population invested more resources into reproduction and also produced more (but smaller) eggs in relation to their body size compared to females from the other population. We suggest that these females have adjusted their reproductive strategies as a counter-adaptation because a high amount of sedimentation on the eggs in that subpopulations spawning habitat might benefit smaller eggs. Collectively, our findings point to adaptive divergence among sympatric subpopulations that are physically separated only for a short period during reproduction and early development – which is rare. These results illustrate how combinations of translocation experiments and field studies of life-history traits might infer about local adaptation and evolutionary divergence among populations. Local adaptations in subdivided populations are important to consider in management and conservation of biodiversity, because they may otherwise be negatively affected by harvesting, supplementation, and reintroduction efforts targeted at endangered populations.
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| 3. |
- Bergqvist, Joakim, et al.
(author)
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Detection and Isolation of Sindbis Virus from Mosquitoes Captured During an Outbreak in Sweden, 2013
- 2015
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In: Vector Borne and Zoonotic Diseases. - : Mary Ann Liebert Inc. - 1530-3667 .- 1557-7759. ; 15:2, s. 133-140
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Journal article (peer-reviewed)abstract
- Mosquito-borne alphaviruses have the potential to cause large outbreaks throughout the world. Here we investigated the causative agent of an unexpected Sindbis virus (SINV) outbreak during August-September, 2013, in a previously nonendemic region of Sweden. Mosquitoes were collected using carbon dioxide-baited CDC traps at locations close to human cases. The mosquitoes were initially screened as large pools by SINV-specific quantitative RT-PCR, and the SINV-positive mosquitoes were species determined by single-nucleotide polymorphism (SNP) analysis, followed by sequencing the barcoding region of the cytochrome oxidase I gene. The proportion of the collected mosquitoes was determined by a metabarcoding strategy. By using novel strategies for PCR screening and genetic typing, a new SINV strain, Lovanger, was isolated from a pool of 1600 mosquitoes composed of Culex, Culiseta, and Aedes mosquitoes as determined by metabarcoding. The SINV-positive mosquito Culiseta morsitans was identified by SNP analysis and sequencing. After whole-genome sequencing and phylogenetic analysis, the SINV Lovanger isolate was shown to be most closely similar to recent Finnish SINV isolates. In conclusion, within a few weeks, we were able to detect and isolate a novel SINV strain and identify the mosquito vector during a sudden SINV outbreak.
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| 4. |
- Forsman, Anders, et al.
(author)
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Pike Esox lucius as an emerging model organism for studies in ecology and evolutionary biology: a review.
- 2015
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In: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 87:2, s. 472-479
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Research review (peer-reviewed)abstract
- The pikeEsox luciusis a large, long-lived, iteroparous, top- predator fish species with a circumpolardistribution that occupies a broad range of aquatic environments. This study reports on a literaturesearch and demonstrates that the publication rate ofE. luciusresearch increases both in absolute termsand relative to total scientific output, and that the focus of investigation has changed over time frombeing dominated by studies on physiology and disease to being gradually replaced by studies on ecol-ogy and evolution.Esox luciuscan be exploited as a model in future research for identifying causes andconsequences of phenotypic and genetic variation at the levels of individuals, populations and speciesas well as for investigating community processes.
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| 5. |
- Gylfe, Åsa, et al.
(author)
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Mosquitoborne Sindbis Virus Infection and Long-Term Illness
- 2018
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In: Emerging Infectious Diseases. - : Centers for Disease Control and Prevention (CDC). - 1080-6040 .- 1080-6059. ; 24:6, s. 1141-1142
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Journal article (peer-reviewed)abstract
- An unexpected human outbreak of the mosquitoborne Sindbis virus occurred in a previously nonendemic area of Sweden. At follow-up, 6-8 months after infection, 39% of patients had chronic arthralgia that affected their daily activities. Vectorborne infections may disseminate rapidly into new areas and cause acute and chronic disease.
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| 6. |
- Hall, Marcus, et al.
(author)
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Intra-population variation in reproductive timing covaries with thermal plasticity of offspring performance in perch Perca fluviatilis
- 2021
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In: Journal of Animal Ecology. - : John Wiley & Sons. - 0021-8790 .- 1365-2656.
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Journal article (peer-reviewed)abstract
- Life history theory posits that organisms should time their reproduction to coincide with environmental conditions that maximize their fitness. Population-level comparisons have contributed important insights on the adaptive value of reproductive timing and its association to environmental variation. Yet, despite its central role to ecology and evolution, the causes and consequences of variation in reproductive timing among individuals within populations are poorly understood in vertebrates other than birds.Using a combination of observational field studies and a split-brood experiment, we investigated whether differences in breeding time were associated with changes in hatching success, reproductive allocation and reaction norms linking offspring performance to temperature within an anadromous Baltic Sea population of perch Perca fluviatilis.Field observations revealed substantial variation in reproductive timing, with the breeding period lasting almost 2 months and occurring in temperatures ranging from 10 to 21°C. The hatching success of perch decreased as the reproductive season progressed. At the same time, the reproductive allocation strategy changed over the season, late breeders (the offspring of which were introduced into a high resource environment and increased predation pressure) produced more and smaller eggs that resulted in smaller larvae, compared with early breeders.The split-brood experiment in which eggs were incubated in different temperatures (10, 12, 15, 18°C) showed that differences in reproductive timing were associated with a change in the shape of the reaction norm linking offspring performance to water temperature indicative of adaptive phenotypic plasticity, with the offspring of early breeders performing best in low temperatures and the offspring of late breeders performing best in high temperatures.The seasonal changes in reproductive traits and the shape of the thermal performance suggest time-dependent adaptive differences among individuals within the population. Management actions aimed at preserving and restoring variation in the timing of reproductive events will thus likely also influence variation in associated life history traits and thermal performance curves, which could safeguard populations against environmental challenges and changes associated with exploitation and global warming.
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| 7. |
- Hall, Marcus, et al.
(author)
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Maternal size in perch (Perca fluviatilis) influences the capacity of offspring to cope with different temperatures
- 2023
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In: Frontiers in Marine Science. - : Frontiers Media S.A.. - 2296-7745. ; 10
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Journal article (peer-reviewed)abstract
- Climate change causes earlier and warmer springs in seasonal environments and a higher incidence of extreme weather events. In aquatic environments, this changes the thermal conditions during spawning, and the thermal performance of eggs and embryos may determine the consequences of climate change on recruitment. In iteroparous species with indeterminate growth, the eggs produced by a given female in successive years will increase in size as the female grows larger and likely be exposed to different temperatures during incubation due to annual variation in spring phenology. Still, we know little about whether differences in maternal size impact the temperature-dependent performance and viability of the offspring. Here we utilised a thermal gradient laboratory experiment on Baltic Sea perch (Perca fluviatilis) to investigate how maternal size influence the temperature dependent hatching success of the offspring. The results uncovered a positive relationship between maternal size and average hatching success, but the shape of the relationship (reaction norm) linking hatching success to incubation temperature was independent of maternal size. However, we did find an association between maternal size and the variance (S.D. and CV) in hatching success across temperatures, with larger females producing offspring with maintained performance (less sensitive) across temperature treatments, indicative of flatter reaction norms and broader thermal niches. This suggests that maintaining the size distribution of fish populations, for instance through regulations of size-selective fisheries, may be important to aid the long-term productivity and viability of fish populations and ultimately conserve the function and services of ecosystems.
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| 8. |
- Larsson, Per, et al.
(author)
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Ecology, evolution, and management strategies of northern pike populations in the Baltic Sea
- 2015
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In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 44:Supplement 3, s. S451-S461
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Research review (peer-reviewed)abstract
- Baltic Sea populations of the northern pike (Esox lucius) have declined since the 1990s, and they face additional challenges due to ongoing climate change. Pike in the Baltic Sea spawn either in coastal bays or in freshwater streams and wetlands. Pike recruited in freshwater have been found to make up about 50 % of coastal pike stocks and to show natal homing, thus limiting gene flow among closely located spawning sites. Due to natal homing, sub-populations appear to be locally adapted to their freshwater recruitment environments. Management actions should therefore not involve mixing of individuals originating from different sub-populations. We offer two suggestions complying with this advice: (i) productivity of extant freshwater spawning populations can be boosted by modifying wetlands such that they promote spawning and recruitment; and (ii) new sub-populations that spawn in brackish water can potentially be created by transferring fry and imprinting them on seemingly suitable spawning environments.
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| 9. |
- Nordahl, Oscar, et al.
(author)
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Genetic differentiation between and within ecotypes of pike (Esox lucius) in the Baltic Sea
- 2019
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In: Aquatic conservation. - : John Wiley & Sons. - 1052-7613 .- 1099-0755. ; 29:11, s. 1923-1935
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Journal article (peer-reviewed)abstract
- Aquatic systems often lack physical boundaries for gene flow, but ecological and behavioural barriers can form surprisingly fine spatial scale genetic patterns that challenge traditional, large scale management. To detect fine spatial scale structures, understand sources of intraspecific diversity, and design appropriate management plans requires identification of reproductively isolated units. This study reports on genetic differentiation in pike (Esox lucius) within a coastal area stretching 55 km from south to north in the central Baltic Sea. Pike is here an economically and ecologically important top predator that has declined in abundance. However, population structures have mostly been studied on large spatial scales, and without considering the potential for genetic divergence between the sympatric anadromous fresh water and the resident brackish water spawning ecotypes. To this end, 487 individuals from the east coast of Sweden and the island of oland, representing sympatric anadromous and resident spawning individuals, categorized to ecotype based on spawning location or otolith microchemistry, were genotyped for 10 microsatellites and used to test for divergence between ecotypes. Furthermore, divergence between regions (island/mainland), neighbouring spawning locations (n = 13) and isolation by distance within and between regions were evaluated for the anadromous ecotype. The results revealed strong genetic differences between regions, between spawning locations separated by as little as 5 km and the first evidence of genetic differentiation between resident and anadromous ecotypes; despite a high dispersal capacity of pike and a high connectivity within the study area. The signatures of isolation by distance indicated that connectivity among populations differed between regions, probably reflecting availability of spawning habitats. To safeguard against the challenges and uncertainties associated with environmental change, adaptive conservation management should aim to promote high intra-population functional genetic diversity without compromising the continued integrity and coexistence of the different ecotypes and of locally adapted sub-populations.
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| 10. |
- Nordahl, Oscar
(author)
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Intraspecific diversity of pike (Esox lucius) in the Baltic Sea and new insights on thermoregulation in fish
- 2018
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Doctoral thesis (other academic/artistic)abstract
- Fish display a fascinating variation in behavior, morphology and physiology among species, among individuals within species, and within individuals over time. A central quest in ecology and evolution is to understand causes and consequences of such variation. This thesis aims to contribute to this knowledge by: (1) investigating the evolutionary processes that shape intraspecific variation among sympatric subpopulations of pike in coastal areas of the Baltic Sea; and (2) exploring whether fish can utilize sun-basking to regulate body temperature and whether this has any consequences for fitness.Identifying barriers that delineate populations is a first step towards evaluating the evolutionary origin of intraspecific variation. This thesis reports on genetic population structures among co-existing pike in the coastal Baltic Sea separated by homing behavior, different spawning strategies and geographic barriers. Field studies revealed that these subpopulations also show phenotypic divergence in reproductive and meristic traits. Experimental studies suggested that differentiation among subpopulations likely was a result of divergent selection and local adaptations to spawning grounds. These adaptations that may further reinforce barriers among subpopulations due to a reduced success of immigrant genotypes.For the second aim of the thesis, we first studied seasonal and diel patterns of activity and vertical migration among the Baltic Sea pike. The results suggested that pike exposed themselves to sunlight during spring and summer, and that body temperatures were positively correlated with sun exposure during these basking events. This was followed by experimental studies on inanimate physical models and a field study on carp which demonstrated that fish can become warmer than ambient water when exposed to sun light, a previously overlooked mechanism for fish thermoregulation, and that the heat gain was positively correlated with growth.This thesis contributes to our understanding of the origin and maintenance of intraspecific variation among coexisting populations with direct implications for management of pike. It also establishes sun-basking as a novel mechanism for fish to obtain body temperatures in excess of ambient water which could motivate adaptations, both evolutionary and plastic, that optimize heat gain, affect spatiotemporal distributions and biotic interaction within and among species.
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