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Avian MHC: variation and selection in the wild

Author

Summary, in English

In vertebrates the Major Histocompatibility Complex (MHC) plays a central role in the specific immune defence against various pathogens. Compared with other coding genes the MHC genes exhibit an extremely high level of polymorphism that is maintained by balancing selection. The importance in the immune defence and the polymorphism make these genes interesting to study from an ecological and evolutionary perspective in populations subject to natural selection. In my thesis I have studied MHC in a population of wild songbirds, great reed warblers Acrocephalus arundinaceus. Firstly, I characterized parts of the MHC class I and II genes and I focused especially on transcribed genes since these are likely to be under selection. Then I developed a PCR-based screening method for investigating the MHC class I polymorphism in our study population. In the great reed warbler genome there was a large number of MHC class I and II genes and there was also evidence of balancing selection in these genes. There was a surprisingly high level of variation in the MHC genes in the great reed warblers within the study population considering the limited variation that have been detected using neutral markers. Secondly, I searched for evidence of selection on the MHC genes and for associations between life-history data and MHC genes. I found evidence that there is selection on the MHC class I alleles in great reed warblers. Avian malaria could be one such selective force since great reed warblers that had a large number of MHC alleles (heterozygous individuals) survived an infection with avian malaria (GRW2) more often than individuals with fewer MHC alleles. Hence, a large number of MHC alleles seem critical for survival. However, we did not find that MHC-compatibility is involved in female mate choice in the great reed warblers, as has been found in humans and mice, despite the fact that more MHC heterozygous great reed warbler siblings do survive more often. Finally, associations between certain MHC alleles, or a large number of MHC alleles, and resistance to specific diseases have so far been found in a handful of species. Most of these associations involve humans or are experiments that have been done under controlled conditions. To me it is compelling that the selection pressure from pathogens on MHC genes can be visualised also under natural conditions in wild populations, as e.g. the great reed warblers.

Publishing year

2003

Language

English

Document type

Dissertation

Publisher

Helena Westerdahl Ecology Building 223 62 Lund,

Topic

  • Biological Sciences

Keywords

  • polymorphism
  • balancing selection
  • cDNA
  • avian malaria
  • great reed warbler
  • Djurekologi
  • bird
  • Animal ecology
  • immune defence
  • MHC class II
  • Major Histocompatibility Complex
  • MHC class I

Status

Published

Project

  • Avian MHC genes

Research group

  • Molecular Ecology and Evolution Lab

Supervisor

  • [unknown] [unknown]

ISBN/ISSN/Other

  • ISBN: 91-7105-192-9

Defence date

10 October 2003

Defence time

10:15

Defence place

Blå Hallen Ekologihuset Lund

Opponent

  • Josephine M Pemberton (Prof)