Abstracts (first author)


Uncovering adaptative differentiation it the wild

Author(s): Merilä J


Differentiating in between adaptive and non adaptive causes of population differentiation in phenotypic traits of ecological interest remains often a challenge for empirical studies of natural populations. I will review a series of yet unpublished empirical studies which have utilized newly developed quantitative genetic approach to differentiate in between natural selection and genetic drift as a cause of population differentiation. Apart from of aiming to illustrate the general utility of this approach, I hope introduce couple of illuminating empirical case-studies where footprints of adaptive differentiation can be recovered in spite of strong influence of genetic drift and gene flow, respectively.


Abstracts (coauthor)


Uncovering the genetic architecture of local adaptations is a central topic in contemporary evolutionary biology. Parallel phenotypic and physiological differentiation in independent populations provides strong evidence for evolution by natural selection. Pond populations of Fennoscandian ninespine sticklebacks, subject to strong genetic drift show parallel phenotypic divergence from their marine conspecifics in several traits (e.g. growth, behavior, body shape) apparently as a result of adaptation to reduced predation-risk. We are investigating genetic mechanisms underlying this parallel phenotypic evolution with the aid of genomic approaches utilizing F2-intercrosses between pond populations and a marine population. One of the main aims is to clarify whether the same (parallel evolution) or different (convergent evolution) genes and genomic regions are responsible for the repeated evolution of pond phenotypes. Targeting this, a high density linkage map based on SNP-markers has been constructed to identify genomic regions responsible for the phenotypic divergence among pond and marine populations. This also opens opportunities for comparative genomic studies among nine- and threespine sticklebacks. In future, linkage and QTL mapping for multiple crosses will give the first insights into genomic regions responsible for parallel phenotypic evolution in ninespine sticklebacks.


Genetic architecture of ecologically important traits, such as behavior and body size, are as yet relatively little studied in wild animals. Using F2-intercross (n = 283 offspring) between behaviorally and growth strategically divergent nine-spined stickleback (Pungitius pungitius) populations, we explored the genetic underpinnings of growth and behavioral traits describing different aspects of activity and boldness with the aid of quantitative trait locus (QTL) analyses based on 226 microsatellite markers. The behaviors were analyzed separately (viz. feeding activity, risk-taking, exploration) and also in combination to map “behavioral types”. Significant (experiment wide) QTLs were detected for both trait groups. In addition, suggestive (chromosome wide) QTLs were also detected. The results also showed that loci affecting size and growth traits were located in some cases in the same chromosomal region as loci affecting behavior of the nine-spined stickleback. The results found in these studies lay the foundations for fine mapping these traits and provide a starting point for identification genes responsible for the size and behavior differences between marine and pond nine-spined sticklebacks.


Recent years have seen a shift in the way we view population structuring in organisms living in marine environments. Once thought of as panmictic and genetically homogenous, marine populations are now realized to have the potential to be subdivided on a finer geographic scale than previously appreciated. Descriptions of variation at genes whose functional roles are associated with specific selection regimes can offer insight towards the scale and degree of adaptive divergence among marine populations, but until recently this approach has traditionally been limited to very few loci. In our research, we use a genome-wide set of 140 microsatellite markers that are within (or close to) genes that have exhibited transcriptional responses to specific environmental conditions, in order to explore the patterns of adaptive population divergence and heterogeneous genomic differentiation among marine threespine sticklebacks (Gasterosteus aculeatus) in Northern European seas. Using 20 of these markers and a much denser sampling scheme, we then further explored adaptive divergence within the environmentally heterogeneous Baltic Sea in relation to the steep salinity and thermal gradients. The results of our candidate genome-scans provide support for the emerging view that, in spite of the high degree of physical connectivity in marine environments, there is a great deal of adaptive divergence among marine populations that is not apparent when neutral loci are analyzed.


Ongoing climate change will expose populations to altered thermal regimens, which are likely to include more frequent and higher temperature maxima. Whether and how a resident population can withstand or adapt to these new conditions will depend on the genetic architecture underlying responses to temperature changes. This includes both coding genes and the regulatory regions that govern expression of these genes. Recent advances enabling the quantification of transcription levels for a large number of genes and the genotyping of many thousands of genetic markers throughout the genome, together with novel statistical methods, are facilitating the identification of such regulatory regions via expression quantitative trait locus (eQTL) analysis.

The threespine stickleback (Gasterosteus aculeatus) is an important model organism in evolutionary biology. The species occurs as resident populations in a wide range of habitats with different thermal profiles. We used sticklebacks derived from the Baltic coast of Finland to identify and localize eQTLs underlying changes in gene expression in response to thermal stress. Experimental subjects comprised 600 individuals in 30 sib–halfsib families, half of which were subject to a thermal challenge immediately prior to tissue collection. Liver mRNA expression was subsequently quantified using Agilent custom microarrays. Over 2000 genes were found to be differentially expressed between control and treatment groups. Genotyping of the families by sequencing on the Illumina platform, in combination with the existing G. aculeatus genome, was used to generate a linkage map that included over 10,000 SNPs. This enabled us to characterize and explore the regulatory networks underlying these changes in gene expression.


Chairman: Octávio S. Paulo
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XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon


Computational Biology & Population Genomics Group