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Can balancing selection on MHC loci counteract genetic drift in small fragmented populations of black grouse?
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology. (Jacob Höglund)
Dept Wildlife Ecology and Management, University Freiburg.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology. Dept of Animal Biology, Plant Biology and Ecology, Faculty of Science, University of A Coruña.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
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2012 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 2, no 2, 341-353 p.Article in journal (Refereed) Published
Abstract [en]

The ability of natural populations to adapt to new environmental conditions is crucial for their survival and partly determined by the standing genetic variation in each population. Populations with higher genetic diversity are more likely to contain individuals that are better adapted to new circumstances than populations with lower genetic diversity. Here we use both neutral and MHC markers to test whether small and highly fragmented populations hold lower genetic diversity than large ones. We use black grouse as it is distributed across Europe and found in populations with varying degrees of isolation and size. We sampled eleven different populations; five continuous, three isolated and three small and isolated. We tested patterns of genetic variation in these populations using three different types of genetic markers: nine microsatellites and 21 SNPs (Single Nucleotide Polymorphisms) which both were found to be neutral, and two functional MHC (Major Histocompatibility Complex) genes that are presumably under selection. The small isolated populations displayed significantly lower neutral genetic diversity compared to continuous populations. A similar trend, but not as pronounced, was found for genotypes at MHC class II loci. Populations were less divergent at MHC genes compared to neutral markers. Measures of genetic diversity and population genetic structure were positively correlated among microsatellites and SNPs, but none of them were correlated to MHC when comparing all populations. Our results suggest that balancing selection at MHC loci does not counteract the power of genetic drift when populations get small and fragmented. 

Place, publisher, year, edition, pages
2012. Vol. 2, no 2, 341-353 p.
Keyword [en]
Fragmentation; genetic drift; MHC; population isolation; SNP
National Category
Ecology Evolutionary Biology Genetics
URN: urn:nbn:se:uu:diva-160034DOI: 10.1002/ece3.86ISI: 000312442500006PubMedID: 22423328OAI: diva2:447856
Swedish Research Council
Available from: 2011-10-13 Created: 2011-10-13 Last updated: 2016-08-11Bibliographically approved
In thesis
1. European Black Grouse: MHC Genetic Diversity and Population Structure
Open this publication in new window or tab >>European Black Grouse: MHC Genetic Diversity and Population Structure
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Black grouse Tetrao tetrix is a bird species composed of large, continuous as well as severely reduced and fragmented populations, making it an optimal species to investigate how genetic diversity is affected by habitat fragmentation. I have focused on genetic diversity in the Major Histocompatibility Complex (MHC) to measure the ability of the black grouse to respond to environmental changes.

I partly characterized MHC class II in black grouse and found striking similarities with chicken MHC class II. I demonstrated that black grouse possess a similar compact MHC as chicken with few MHC class II B (BLB) and Y (YLB) loci. I did not find evidence of balancing selection in YLB so I concentrated further studies on BLB.

I developed a PCR-based screening method for amplifying and separating expressed BLB alleles in European black grouse populations. Small fragmented populations had lost neutral genetic diversity (based on microsatellites and SNPs) compared to samples from the historical distribution and contemporary large populations. There was also a trend, albeit less pronounced, for reduced MHC diversity in these populations. Neutral markers in small isolated populations were affected by increased levels of genetic drift and were therefore genetically differentiated compared to other populations. MHC markers on the other hand, were not subjected to genetic drift to the same extent probably due a long historic process of balancing selection.

Inferences of heterozygosity and evolutionary patterns as well as detailed correlations to reproductive success and diseases cannot be performed until MHC can be amplified in a locus-specific manner. Therefore, I developed a single locus sequence-based typing method for independently amplifying MHC class II B loci (BLB1 and BLB2). I found that BLB1 and BLB2 were duplicated in a common ancestor to chickens and black grouse and that these loci are subjected to homogenizing concerted evolution due to inter-genetic exchange between loci after species divergence.  I could also verify that both BLB1 and BLB2 were transcribed in black grouse and under balancing selection.

This collection of work has significance for future conservation of black grouse as well as research and management of zoonotic diseases.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 59 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 869
Major Histocompatibility Complex, BLB, balancing selection, concerted evolution, bottleneck, fragmentation, 3'UTR
National Category
Evolutionary Biology Ecology Genetics
Research subject
Biology with specialization in Population Biology
urn:nbn:se:uu:diva-160042 (URN)978-91-554-8188-9 (ISBN)
Public defence
2011-11-25, Zootissalen, Evolutionary Biology Centre, Villavägen 9, Uppsala, 09:15 (English)
Available from: 2011-11-04 Created: 2011-10-13 Last updated: 2011-11-10Bibliographically approved

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