| 1. |
- Andersson, Anastasia, et al.
(författare)
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Complex genetic diversity patterns of cryptic, sympatric brown trout (Salmo trutta) populations in tiny mountain lakes
- 2017
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 18:5, s. 1213-1227
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Tidskriftsartikel (refereegranskat)abstract
- Intraspecific genetic variation can have similar effects as species diversity on ecosystem function; understanding such variation is important, particularly for ecological key species. The brown trout plays central roles in many northern freshwater ecosystems, and several cases of sympatric brown trout populations have been detected in freshwater lakes based on apparent morphological differences. In some rare cases, sympatric, genetically distinct populations lacking visible phenotypic differences have been detected based on genetic data alone. Detecting such cryptic sympatric populations without prior grouping of individuals based on phenotypic characteristics is more difficult statistically, though. The aim of the present study is to delineate the spatial connectivity of two cryptic, sympatric genetic clusters of brown trout discovered in two interconnected, tiny subarctic Swedish lakes. The structures were detected using allozyme markers, and have been monitored over time. Here, we confirm their existence for almost three decades and report that these cryptic, sympatric populations exhibit very different connectivity patterns to brown trout of nearby lakes. One of the clusters is relatively isolated while the other one shows high genetic similarity to downstream populations. There are indications of different spawning sites as reflected in genetic structuring among parr from different creeks. We used > 3000 SNPs on a subsample and find that the SNPs largely confirm the allozyme pattern but give considerably lower F (ST) values, and potentially indicate further structuring within populations. This type of complex genetic substructuring over microgeographical scales might be more common than anticipated and needs to be considered in conservation management.
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| 2. |
- Andersson, Anastasia, et al.
(författare)
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Lack of trophic polymorphism despite substantial genetic differentiation in sympatric brown trout (Salmo trutta) populations
- 2017
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Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 26:4, s. 643-652
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Tidskriftsartikel (refereegranskat)abstract
- Sympatric populations occur in many freshwater fish species; such populations are typically detected through morphological distinctions that are often coupled to food niche and genetic separations. In salmonids, trophic and genetically separate sympatric populations have been reported in landlocked Arctic char, whitefish and brown trout. In Arctic char and brown trout rare cases of sympatric, genetically distinct populations have been detected based on genetic data alone, with no apparent morphological differences, that is cryptic structuring. It remains unknown whether such cryptic, sympatric structuring can be coupled to food niche separation. Here, we perform an extensive screening for trophic divergence of two genetically divergent, seemingly cryptic, sympatric brown trout populations documented to remain in stable sympatry over several decades in two interconnected, tiny mountain lakes in a nature reserve in central Sweden. We investigate body shape, body length, gill raker metrics, breeding status and diet (stomach content analysis and stable isotopes) in these populations. We find small significant differences for body shape, body size and breeding status, and no evidence of food niche separation between these two populations. In contrast, fish in the two lakes differed in body shape, diet, and nitrogen and carbon isotope signatures despite no genetic difference between lakes. These genetically divergent populations apparently coexist using the same food resources and showing the same adaptive plasticity to the local food niches of the two separate lakes. Such observations have not been reported previously but may be more common than recognised as genetic screenings are necessary to detect the structures.
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| 3. |
- Guban, Peter, et al.
(författare)
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Genetic diversity in Monoporeia affinis at polluted and reference sites of the Baltic Bothnian Bay
- 2015
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Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 93:1-2, s. 245-249
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Tidskriftsartikel (refereegranskat)abstract
- The amphipod Monoporeia affinis plays an important role in the Baltic Sea ecosystem as prey and as detritivore. The species is monitored for contaminant effects, but almost nothing is known about its genetics in this region. A pilot screening for genetic variation at the mitochondrial COI gene was performed in 113 individuals collected at six sites in the northern Baltic. Three coastal sites were polluted by pulp mill effluents, PAHs, and trace metals, and two coastal reference sites were without obvious connection to pollution sources. An off-coastal reference site was also included. Contaminated sites showed lower levels of genetic diversity than the coastal reference ones although the difference was not statistically significant. Divergence patterns measured as Phi(ST) showed no significant differentiation within reference and polluted groups, but there was significant genetic divergence between them. The off-coastal sample differed significantly from all coastal sites and also showed lower genetic variation.
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| 4. |
- Hill, Jason, et al.
(författare)
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Recurrent convergent evolution at amino acid residue 261 in fish rhodopsin
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:37, s. 18473-18478
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Tidskriftsartikel (refereegranskat)abstract
- The evolutionary process that occurs when a species colonizes a new environment provides an opportunity to explore the mechanisms underlying genetic adaptation, which is essential knowledge for understanding evolution and the maintenance of biodiversity. Atlantic herring has an estimated total breeding stock of about 1 trillion (10(12)) and has colonized the brackish Baltic Sea within the last 10,000 y. Minute genetic differentiation between Atlantic and Baltic herring populations at selectively neutral loci combined with this rapid adaptation to a new environment facilitated the identification of hundreds of loci underlying ecological adaptation. A major question in the field of evolutionary biology is to what extent such an adaptive process involves selection of novel mutations with large effects or genetic changes at many loci, each with a small effect on phenotype (i.e., selection on standing genetic variation). Here we show that a missense mutation in rhodopsin (Phe261Tyr) is an adaptation to the red-shifted Baltic Sea light environment. The transition from phenylalanine to tyrosine differs only by the presence of a hydroxyl moiety in the latter, but this results in an up to 10-nm red-shifted light absorbance of the receptor. Remarkably, an examination of the rhodopsin sequences from 2,056 species of fish revealed that the same missense mutation has occurred independently and been selected for during at least 20 transitions between light environments across all fish. Our results provide a spectacular example of convergent evolution and how a single amino acid change can have a major effect on ecological adaptation.
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| 5. |
- Hössjer, Ola, et al.
(författare)
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Effective sizes and time to migration-drift equilibrium in geographically subdivided populations
- 2016
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Ingår i: Theoretical Population Biology. - : Elsevier BV. - 0040-5809 .- 1096-0325. ; 112, s. 139-156
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Tidskriftsartikel (refereegranskat)abstract
- Many versions of the effective population size (N-e) exist, and they are important in population genetics in order to quantify rates of change of various characteristics, such as inbreeding, heterozygosity, or allele frequencies. Traditionally, N-e was defined for single, isolated populations, but we have recently presented a mathematical framework for subdivided populations. In this paper we focus on diploid populations with geographic subdivision, and present new theoretical results. We compare the haploid and diploid versions of the inbreeding effective size (N-ei) with novel expression for the variance effective size (N-ev), and conclude that for local populations N-ev is often much smaller than both versions of Nei, whenever they exist. Global N(ev)of the metapopulation, on the other hand, is close to the haploid Net and much larger than the diploid Nei. We introduce a new effective size, the additive genetic variance effective size Neill', which is of particular interest for long term protection of species. It quantifies the rate at which additive genetic variance is lost and we show that this effective size is closely related to the haploid version of Nei. Finally, we introduce a new measure of a population's deviation from migration-drift equilibrium, and apply it to quantify the time it takes to reach this equilibrium. Our findings are of importance for understanding the concept of effective population size in substructured populations and many of the results have applications in conservation biology.
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| 6. |
- Hössjer, Ola, et al.
(författare)
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Metapopulation inbreeding dynamics, effective size and subpopulation differentiation-A general analytical approach for diploid organisms
- 2015
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Ingår i: Theoretical Population Biology. - : Elsevier BV. - 0040-5809 .- 1096-0325. ; 102, s. 40-59
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by problems in conservation biology we study genetic dynamics in structured populations of diploid organisms (monoecious or dioecious). Our analysis provides an analytical framework that unifies substantial parts of previous work in terms of exact identity by descent (IBD) and identity by state (IBS) recursions. We provide exact conditions under which two structured haploid and diploid populations are equivalent, and some sufficient conditions under which a dioecious diploid population can be treated as a monoecious diploid one. The IBD recursions are used for computing local and metapopulation inbreeding and coancestry effective population sizes and for predictions of several types of fixation indices over different time horizons.
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| 7. |
- Jansson, Mija, et al.
(författare)
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Genetic contribution from a zoo population can increase genetic variation in the highly inbred wild Swedish wolf population
- 2015
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 16:6, s. 1501-1505
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish wolf population (Canis lupus) descends from five individuals and is isolated and highly inbred with an average inbreeding coefficient of 0.27. In addition, inbreeding depression has led to reduced litter size and a high frequency of spinal disorders. To achieve the management goal of reducing the mean level of inbreeding, introductions into the wild population from a zoo conservation breeding program have been proposed by authorities. We used pedigree data of the wild and zoo populations to evaluate the extent to which the captive population can contribute genetic variation to the wild one. We measure genetic variation as founder alleles and founder genome equivalents. The two populations have three founders in common, but in spite of this common ancestry, our results show a potential to almost double genetic variation from 11.2 to 21.1 founder alleles. Similarly, the number of founder genome equivalents in the wild population can increase from the present 1.8 to 3.2, but this requires that almost 50 % of the wild gene pool consists of genes from the zoo population. Average kinship in the joint zoo and wild population is 0.15, which is above the management target of 0.1. Genetic contribution from the zoo has the potential to improve, but not solve, the genetically precarious situation of the wild population.
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| 8. |
- Jansson, Mija, et al.
(författare)
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Pedigree data indicate rapid inbreeding and loss of genetic diversity within populations of native, traditional dog breeds of conservation concern
- 2018
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 13:9
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Tidskriftsartikel (refereegranskat)abstract
- Increasing concern is directed towards genetic diversity of domestic animal populations because strong selective breeding can rapidly deplete genetic diversity of socio-economically valuable animals. International conservation policy identifies minimizing genetic erosion of domesticated animals as a key biodiversity target. We used breeding records to assess potential indications of inbreeding and loss of founder allelic diversity in 12 native Swedish dog breeds, traditional to the country, ten of which have been identified by authorities as of conservation concern. The pedigrees dated back to the mid-1900, comprising 5-11 generations and 350-66,500 individuals per pedigree. We assessed rates of inbreeding and potential indications of loss of genetic variation by measuring inbreeding coefficients and remaining number of founder alleles at five points in time during 1980-2012. We found average inbreeding coefficients among breeds to double-from an average of 0.03 in 1980 to 0.07 in 2012 -in spite of the majority of breeds being numerically large with pedigrees comprising thousands of individuals indicating that such rapid increase of inbreeding should have been possible to avoid. We also found indications of extensive loss of intra-breed variation; on average 70 percent of founder alleles are lost during 1980-2012. Explicit conservation goals for these breeds were not reflected in pedigree based conservation genetic measures; breeding needs to focus more on retaining genetic variation, and supplementary genomic analyses of these breeds are highly warranted in order to find out the extent to which the trends indicated here are reflected over the genomes of these breeds.
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| 9. |
- Jorde, Per Erik, et al.
(författare)
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Are we underestimating the occurrence of sympatric populations?
- 2018
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 27:20, s. 4011-4025
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Tidskriftsartikel (refereegranskat)abstract
- Sympatric populations are conspecific populations that coexist spatially. They are of interest in evolutionary biology by representing the potential first steps of sympatric speciation and are important to identify and monitor in conservation management. Reviewing the literature pertaining to sympatric populations, we find that most cases of sympatry appear coupled to phenotypic divergence, implying ease of detection. In comparison, phenotypically cryptic, sympatric populations seem rarely documented. We explore the statistical power for detecting population mixtures from genetic marker data, using commonly applied tests for heterozygote deficiency (i.e., Wahlund effect) and the structure software, through computer simulations. We find that both tests are efficient at detecting population mixture only when genetic differentiation is high, sample size and number of genetic markers are reasonable and the sympatric populations happen to occur in similar proportions in the sample. We present an approximate expression based on these experimental factors for the lower limit of F-ST, beyond which power for structure collapses and only the heterozygote-deficiency tests retain some, although low, power. The findings suggest that cases of cryptic sympatry may have passed unnoticed in population genetic screenings using number of loci typical of the pre-genomics era. Hence, cryptic sympatric populations may be more common than hitherto thought, and we urge more attention being diverted to their detection and characterization.
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| 10. |
- Kurland, Sara, et al.
(författare)
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Exploring a Pool-seq-only approach for gaining population genomic insights in nonmodel species
- 2019
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 9, s. 11448-11463
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Tidskriftsartikel (refereegranskat)abstract
- Developing genomic insights is challenging in nonmodel species for which resources are often scarce and prohibitively costly. Here, we explore the potential of a recently established approach using Pool-seq data to generate a de novo genome assembly for mining exons, upon which Pool-seq data are used to estimate population divergence and diversity. We do this for two pairs of sympatric populations of brown trout (Salmo trutta): one naturally sympatric set of populations and another pair of populations introduced to a common environment. We validate our approach by comparing the results to those from markers previously used to describe the populations (allozymes and individual-based single nucleotide polymorphisms [SNPs]) and from mapping the Pool-seq data to a reference genome of the closely related Atlantic salmon (Salmo salar). We find that genomic differentiation (F-ST) between the two introduced populations exceeds that of the naturally sympatric populations (F-ST = 0.13 and 0.03 between the introduced and the naturally sympatric populations, respectively), in concordance with estimates from the previously used SNPs. The same level of population divergence is found for the two genome assemblies, but estimates of average nucleotide diversity differ (pi over bar approximate to 0.002 and pi over bar approximate to 0.001 when mapping to S. trutta and S. salar, respectively), although the relationships between population values are largely consistent. This discrepancy might be attributed to biases when mapping to a haploid condensed assembly made of highly fragmented read data compared to using a high-quality reference assembly from a divergent species. We conclude that the Pool-seq-only approach can be suitable for detecting and quantifying genome-wide population differentiation, and for comparing genomic diversity in populations of nonmodel species where reference genomes are lacking.
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