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Laboratory:
Division of Population Genetics, Stockholm University, Sweden.
Contact person (name and e-mail):
Persons working on brown trout population genetics:
Nils Ryman (Prof.), Linda Laikre (PhD), Per Erik Jorde (PhD), Stefan Palm (Grad. student)
General research topics of the laboratory:
Conservation and management, genetic population structure, phylogeography, quantitative genetics.
General description of research on brown trout population genetics:
Research at the Division of Population Genetics focuses on problems related to the intraspecific genetic structure of natural populations, their evolutionary and reproductive relationships, and the factors determining the amount and distribution of genetic variation among them. Particular attention is directed towards conservation genetics and to the genetic effects of man's impact on natural populations. The research includes both empirical and theoretical approaches, and current research methodology include: laboratory analysis of DNA, computer simulation, and the development of theoretical and statistical methods. The Division is the only free-standing higher education department in Sweden specialising in population genetics.

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List of projects (brown trout) for the past 3 years:

 

Study #1
Researcher: N. Ryman, P.E. Jorde, L. Laikre, S. Palm
Source of project funding: Swedish Natural Science Research Council (NFR)
Topic: Conservation and management, genetic population structure.
Objective: Long-term genetic/ecologic study of natural brown trout populations in a protected area in northern Sweden. The aim is to illuminate how natural populations function genetically. Several issues have been addressed using the data collected so far, and the results will be of practical significance for fish conservation in general. For instance, theory developed at the Division for estimating effective population size when generations are overlapping has been applied to empirical data accumulated within the project.
Design: The same natural and introduced populations are sampled annually. Tissue samples (muscle, liver, eye) and data on age, sex, length, weight and is collected for every individual.
Methodology: Allozymes, mtDNA RFLP, theory development, statistical analyses.
Trout population: Hatchery stocks, resident and potadromous populations.
Origin of samples: Sweden, Baltic Sea Basin.
Status: Ongoing, long term study.

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Study #2
Researcher: N. Ryman, L. Laikre, S. Palm
Source of project funding: Foundation for Strategic Environmental Research (MISTRA).
Topic: Conservation and management, genetic monitoring, stock enhancement, supportive breeding.
Objective: The release of hatchery fish into the wild (stocking) is practised extensively within the field of fishery management. Stocking may result in a series of genetic interactions between the hatchery-bred fish and natural populations. The genetic integrity of wild populations is threatened not only when releasing fish with an exotic genetic background - loss of genetic variation may occur also when the released fish originate from, or belong to, the recipient population (so-called supportive breeding). Nevertheless, the genetic effects of breeding-release activities on the genetic composition of natural populations are poorly understood. The aim of the project is to produce information that makes it possible to reduce or eliminate the harmful effects on biodiversity on the gene level that are potentially inherent to stocking activities.
Design: Theory development and computer simulations. Anadromous brown trout populations from the Baltic Sea will be used as a model system.
Methodology: Allozymes, theory development, computer simulations.
Trout population: Anadromous populations.
Origin of samples: Sweden (Gotland Island), Baltic Sea Basin.
Status: Started in 1997.

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Study #3
Researcher: N. Ryman, S. Palm
Source of project funding: Swedish Natural Science Research Council (NFR).
Topic: Conservation and management, stocking efficiency, genetic monitoring, stock enhancement, quantitative genetics.
Objective: Studies of molecular genetic markers have added relatively little to the understanding of the genetic basis for variation in phenotypic traits. Here the existence of genetically determined phenotypic differences between populations of brown trout that are divergent at electrophoretically detectable protein loci is investigated.
Design: Genetically tagged individuals from two stocks exhibiting behavioral and ecological differences have been introduced into a drainage system previously void of brown trout. In the common environment the presence of phenotypic differences among different groups of offspring is expected to reflect genetically determined dissimilarities between the original stocks.
Methodology: Allozymes.
Trout population: Hatchery stocks, resident populations.
Origin of samples: Sweden, Baltic Sea Basin.
Status: Ongoing, long term study.

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Study #4
Researcher: N. Ryman, S. Palm
Source of project funding: Swedish Natural Science Research Council (NFR).
Topic: Conservation and management, introgression, genetic monitoring, genetic population structure, estimation of effective population size, natural hybridisation, temporal variation, quantitative genetics.
Objective: Release of genetically modified organisms poses a potential threat to wild populations. Important information on the spread of genes can be obtained through the study of gene introgression via organisms which are not genetically altered. By not using "real" transgenic organisms risks are avoided and costs minimized.
Design: Two genetically different stocks of brown trout have been translocated into a natural lake system (cf. study #3). The introgression of genes from these stocks to naturally occurring brown trout populations is studied.
Methodology: Allozymes.
Trout population: Hatchery stocks, resident and potadromous populations.
Origin of samples: Sweden, Baltic Sea Basin.
Status: Ongoing, long term study.

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Study #5
Researcher: L. Laikre
Source of project funding: County administrative board of Värmland (Länsstyrelsen, Värmland).
Topic: Conservation and management, genetic monitoring, genetic population structure, genetic diversity, temporal variation.
Objective: To address the problems of monitoring biological diversity at the gene level using natural brown trout populations in the Province of Värmland.
Design: Genetic analysis of selected brown trout populations.
Methodology: Allozymes.
Trout population: Resident and potadromous populations.
Origin of samples: Sweden, North Sea Basin.
Status: Started 1997.

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Study #6
Researcher: L. Laikre
Source of project funding: Erik Philip-Sörensens Stiftelse.
Topic: Conservation and management, estimation of effective population size, genetic population structure, temporal variation.
Objective: Information regarding the temporal dynamics of alleles at genetic marker loci in natural populations is exceedingly sparse. Typically, population genetic investigations include sampling at one particular occasion only. This fairly limited knowledge of the extent of temporal variation of DNA markers influences the interpretation of observed spatial patterns; it is largely unclear if they are stable over time. In this project temporal shifts of mtDNA haplotypes in natural brown trout populations in the Province of Jämtland is studied. The amount of genetic drift over several consecutive cohorts (year classes) is quantified and provides the basis for estimating female effective size in these populations. The extent of mtDNA haplotype frequency change is compared with the corresponding allele frequency changes at nuclear (allozyme) loci for the same populations and cohorts.
Design: Tissue sample collections from natural brown trout populations over several years. Genetic analyses of the samples followed by data analyses involving application of theory developed within other projects at the Division of Population Genetics.
Methodology: Allozymes, mtDNA RFLP.
Trout population: Resident and potadromous populations.
Origin of samples: Sweden, Baltic Sea Basin.
Status: Started in 1998.

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Publications (brown trout genetics)

Journal papers:

  • Allendorf, F.W., Mitchell, N., Ryman, N. & Ståhl, G. (1977). Isozyme loci in brown trout (Salmo trutta L.): Detection and interpretation from population data. Hereditas, 86,179-190.
  • Allendorf, F.W., Ryman, N., Stennek, A. & Ståhl, G. (1976). Genetic variation in Scandinavian brown trout (Salmo trutta L.): Evidence of distinct sympatric populations. Hereditas, 83,73-82.
  • Allendorf, F.W., Ståhl, G. & Ryman, N. (1984). Silencing of duplicate genes: A null allele polymorphism for lactate dehydrogenase in brown trout (Salmo trutta). Mol. Biol. Evol., 1,238-248.
  • Chakraborty, R., Haag, M., Ryman, N. & Ståhl, G. (1982). Hierarchical gene diversity analysis and its application to brown trout population data. Hereditas, 97, 17-21.
  • Garcia-Marin, J.L., Jorde, P.E., Ryman, N., Utter, F. & Pla, C. (1991). Management implications of genetic differentiation between native and hatchery populations of brown trout (Salmo trutta) in Spain. Aquaculture, 95, 235-249.
  • Hindar, K., Jonsson, B., Ryman, N. & Ståhl, G. (1991). Genetic relationships among landlocked, resident, and anadromous brown trout, Salmo trutta L. Heredity, 66, 83-91.
  • Jorde, P.E. & Ryman, N. (1990). Allele frequency estimation at loci with incomplete co-dominant expression. Heredity, 65, 429-433.
  • Jorde, P.E. & Ryman, N. (1996). Demographic genetics of brown trout (Salmo trutta) and estimation of effective population size from temporal change of allele frequencies. Genetics, 143,1369-1381.
  • Jorde, P.E., Gitt, A. & Ryman, N. (1991). New biochemical genetic markers in the brown trout (Salmo trutta L.). J. Fish Biol., 39, 451-454.
  • Laikre, L., Jorde, P.E. & Ryman, N. (1998). Temporal change of mitochondrial DNA haplotype frequencies and female effective size in a brown trout (Salmo trutta) population. Evolution, 52, in press.
  • Laikre, L., Prodöhl, P.A., Jorde, P.E. & Ryman, N. (1995). Genetic variability at minisatellite and allozyme loci in brown trout (Salmo trutta) - A comparison. Hereditas, 123, 191-195.
  • Ryman, N. (1981). Conservation of genetic resources: experiences from the brown trout (Salmo trutta). In: Fish gene pools. Ecological Bulletins 34 (Ryman N, ed.), pp. 61--74. Editorial Service, FRN, Stockholm.
  • Ryman, N. (1983). Patterns of distribution of biochemical genetic variation in salmonids: differences between species. Aquaculture, 33, 1-21.
  • Ryman, N. & Ståhl, G. (1980). Genetic changes in hatchery stocks of brown trout (Salmo trutta). Can. J. Fish. Aquat. Sci., 37, 82-87.
  • Ryman, N. & Ståhl, G. (1981). Genetic perspectives of the identification and conservation of Scandinavian stocks of fish. Can. J. Fish. Aquat. Sci., 38, 1562-1575.
  • Ryman, N., Allendorf, F.W. & Ståhl, G. (1979). Reproductive isolation with little genetic divergence in sympatric populations of brown trout (Salmo trutta). Genetics, 92, 247-262.
  • Ryman, N., Ståhl, G. & Öhman, R. (1977). Öring, ärftlighet, fiskevård. Svenskt Fiske, 7-8/1977, 8-10.
  • Ståhl, G. & Gyllensten, U. (1980). Tillsammans men åtskilda: Om genetisk variation i naturen. Forskning och Framsteg, 5, 1-6.
  • Ståhl, G. & Ryman, N. (1982). Simple Mendelian inheritance at a locus coding for alpha-glycerophosphate dehydrogenase in brown trout (Salmo trutta). Hereditas, 96,313-315.

Technical Reports:

  • Jorde, P.E. (1994). Allozymes in Scandinavian brown trout (Salmo trutta, L.). Report, Division of Population Genetics, Stockholm University.
  • Laikre, L. (1995). Genresurser hos naturliga fiskbestånd, resultat från långtidsstudier i Jämtland. (Genetic resources in natural fish-stocks, results from long term studies in Jämtland (In Swedish)). Forskningsinformation, enheten för populationsgenetik, Stockholms universitet.
  • Ryman, N. Öhman, R. Ståhl, G. Nilsson, A. Lagercrantz & Herlitz, A. (1986). Genetisk variation hos laxartad fisk - en snabbt försvinnande naturresurs: Information om genetisk forskning i Jämtland. (Genetic variation in salmonid fishes - a rapidly declining natural resource: Information on the scientific work in the lakes Bävervattnen area in Jämtland, central Sweden (In Swedish)). Resta Grafiska AB, Stockholm.
  • Ståhl, G. & Ryman, N. (1979). Populationsgenetisk analys av öringen i Lulejaureområdet. Genetiska institutionen, Stockholms universitet, Rapport 1.
  • Ståhl, G. & Ryman, N. (1987). Lax och öring i Vänernområdet. En populationsgenetisk analys. (Salmon and trout in the Lake Vänern area. A population genetic analysis. (In Swedish)). Statens naturvårdsverk Rapport 3357, 48 pp.

Theses (eg, PhD and MSc theses):

  • Jorde, P.E. (1995). Temporal allele frequency change in populations with overlapping generations: Estimation of effective size of natural populations as exemplified using brown trout (Salmo trutta). Ph.D. thesis, Division of Population Genetics, Stockholm University.
  • Ståhl, G. (1980). Genetic variation in two closely related salmonids, brown trout (Salmo trutta) and Atlantic salmon (S. salar): a comparison of variability patterns and some management considerations. Ph.D. thesis, Department of Genetics, University of Stockholm.

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