Three spined stickleback - Gasterosteus aculeatus



Summary of issues specific to the Baltic region

Despite the fact that Baltic Sea has been colonized relatively recently, the three-spined stickleback display strong adaptive differentiation both genetically and phenotypically within this area. While it may be early to say whether this stipulates any specific management actions in respect to this species, the fact that lot of differentiation has been uncovered from three-spined stickleback raises the issue if similar differentiation occurs in less well-studied species. One should note that in respect to available genetic resources, there is no match among the other Baltic Sea species studied so far. Therefore, also the likelihood of uncovering adaptive differentiation in the three-spined stickleback is higher than in other species.

Current management regulations

None. In may interesting to note that three-spined stickleback used to have economic importance during the first-half of the 1900-centrury when it was used for fish oil extraction? Only in Gulf of Finland, over 130 000 tons of three-spined sticklebacks were fished yearly.

Gaps between management and scientific evidence

Number and biomass wise the three-spined stickleback is one of the most abundant fish species in Baltic Sea after herring and sprat. It can be hence anticipated that the it is ecologically very important species in the Baltic Sea ecosystem


Species Number of genetic studies Baltic population structure Baltic population diversity Baltic effective population size Temporal data Genetic risks Management recommendations
Three spined stickleback 6-9 Weak structuring in neutral genes, strong structuring in physiologically important genes  High levels of genetic diversity  Not known – most likely high  Museum samples available.  Not known  None


Mapping Baltic Sea genetic biodiversity

These maps show mean differentiation of populations, and location of major genetic discontinuities in threespine stickleback (Gasterosteus aculeatus).


Fig 1. Barriers of gene flow

Three major barriers to genetic exchange was observed for the threespine stickleback.

Full lines are barriers supported by at least half of the scored gene loci. Dotted lines are barriers supported by less than half of the scored loci.

A major genetic barrier is located at the entrance of the Baltic Sea for threespine stickleback.


Fig 2. Genetic divergence

The degree of genetic divergence among populations was classified.

Red dots: populations more genetically divergent than the average divergence among populations.

Blue dots: populations less genetically divergent than the average.

Peripheral populations are generally more diverged (more genetically unique) than central populations.

These are preliminary results (January 2012). Full and additional results on Baltic Sea genetic biodiversity will be presented in a coming scientific report. 

Summary of key published genetic information

The BALTGENE project has collected genetic information from about 45 different Baltic Sea three-spined sticklebacks populations, much of which remains yet to be published. The genetic studies done so far have utilized mitochondrial DNA, microsatellite (over 150 loci) and SNP (ca. 109) information. The general picture emerging from these studies is that the three-spined sticklebacks are only weakly structured in neutral genetic markers over the whole Baltic Sea area, and that the levels of genetic variability are high in all populations. However, when it comes loci linked to genes of morphological or physiological importance, there is substantial small scale differentiation within the Baltic Sea. There is also quantitative genetic evidence to show that there is large degree of genetic differentiation in key genes coding ecologically important traits only within the relative restricted area of the Gulf of Finland.

Quantitative genetic studies have further revealed that there is lot of genetic variation and relatively high heritability of many phenotypic and ecologically important traits in the Helsinki population which has been subject to detailed quantitative genetic studies.

Key publications

Cano J.M, H. Mäkinen & J. Merilä (2008). Genetic evidence for male-biased dispersal in the three-spined stickleback (Gasterosteous aculeatus). Molecular Ecology 17: 3234-3242.

DeFaveri J., T. Shikano, N. I. Ab Ghani & J. Merilä. Contrasting population structures in two sympatric fishes in the Baltic Sea basin. Submitted manuscript.

Leder EH, Cano JM, Leinonen T, O’Hara RB, Nikinmaa M, Primmer CR, Merilä J. (2010) Female-biased expression on the X chromosome as a key step in sex chromosome evolution in Threespine sticklebacksMolecular Biology and Evolution 27: 1495-1503. PubMed

Mäkinen, H., J.M. Cano & J. Merilä (2006) Genetic relationships among marine and freshwater populations of the European three-spined sticklebacks (Gasterosteus aculeatus) revealed by microsatellites. Molecular Ecology 15: 1519-1534.

Mäkinen, H.S. & J. Merilä (2008) Mitochondrial DNA phylogeography of the three-spined stickleback (Gasterosteus aculeatus) in Europe – evidence for multiple glacial refugia. Molecular Phylogenetics and Evolution 46:167-182. 

More information about the three spined stickleback at IUCN - International Union for Conservation of Natural Resources


CONTRIBUTORS (January 2012)
Juha Merilä and Jaqueline DeFaveri, University of Helsinki, Finland
Linda Laikre and Lovisa Wennerström, Stockholm University, Sweden

Responsible editor: Juha Merilä, University of Helsinki, Finland
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