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Avian MHC: variation and selection in the wild

Författare:
Publiceringsår: 2003
Språk: Engelska
Sidor: 146
Dokumenttyp: Doktorsavhandling
Förlag: Helena Westerdahl Ecology Building 223 62 Lund,
Ytterligare information: Article: I Westerdahl, H., Wittzell, H. and von Schantz, T. 1999. Polymorphism and transcription of Mhc class I genes in a passerine bird, the great reed warbler. – Immunogenetics 49: 158–170. Article: II Westerdahl, H., Wittzell, H. and von Schantz, T. 2000. Mhc diversity in two passerine birds: no evidence for a minimal essential Mhc.– Immunogenetics 52: 92–100. Article: III Westerdahl, H., Wittzell, H., von Schantz, T. and Bensch, S. 2003. MHC class I typing in a songbird with numerous loci and high polymorphism using motif-specific PCR and DGGE. – Submitted. Article: IV Richardson, D. S. and Westerdahl, H. 2003. MHC diversity in two Acrocephalus species: the outbred Great reed warbler and the inbred Seychelles warbler. – In press Molecular Ecology. Article: V Westerdahl, H., Hansson, B., Bensch, S. and Hasselquist, D. 2003. Between-year variation of MHC allele frequencies in great reed warblers: selection or drift? – Submitted. Article: VI Westerdahl, H. No evidence of an MHC based female mating preference in great reed warblers. – Manuscript. Article: VII Hansson, B., Westerdahl, H., Hasselquist, D., Åkesson, M. and Bensch, S. 2003. Linkage disequilibria generate heterozygosity-fitness correlations in Great reed warblers. – Submitted. Article: VIII Westerdahl, H., Waldenström, J., Hansson, B., Hasselquist, D., von Schantz, T. and Bench, S. Associations between avian malaria and MHC class I alleles. – Manuscript.

Sammanfattning

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.

Disputation

2003-10-10
10:15
Blå Hallen Ekologihuset Lund
  • Josephine M Pemberton (Prof)

Nyckelord

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

Övriga

  • Molecular Ecology and Evolution Lab
  • ISBN: 91-7105-192-9

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