Abstract
All organisms need to fight pathogens to avoid infectious diseases. In vertebrates, two classes of polymorphic genes from the major histocompatibility complex (MHC) are crucial for triggering immune responses against specific intracel-lular (MHC class I; MHCI) and extracellular (MHC class II; MHCII) pathogens. Whenever possible, females should choose mates that render an optimal MHC constitution in the offspring. Such genetic effects of mate choice can be elu-cidated by studying species where females engage in extra-pair mating. This thesis explores MHC-based extra-pair mate choice in two songbirds, using new sequencing technology. The hypervariable songbird MHC has been difficult to geno-type, but new methodology offers great improvements. For the bluethroat (Luscinia svecica), evidence for non-random, self-referential female choice of extra-pair males based on an intermediate optimum in MHCII diversity was found. For the willow warbler (Phylloscopus trochilus), females with few MHCI variants were more likely to engage in extra-pair mating. This thesis sheds light on the variation in MHC-based mate choice, and demonstrate an adaptive benefit of fe-male extra-pair mating in songbirds.
List of papers
Paper I: Rekdal SL, Anmarkrud JA, Johnsen A and Lifjeld JT (2018). Genotyping strategy matters when analyzing hypervariable major histocompatibility complex ‐ Experience from a passerine bird. Ecology and evolution 8(3): 1680-1692. doi: 10.1002/ece3.3757. The article is included in the thesis. Also available at: https://doi.org/10.1002/ece3.3757 |
Paper II: Rekdal SL, Anmarkrud JA, Lifjeld JT and Johnsen A (2019). Extra-pair mating in a passerine bird with highly duplicated major histocompatibility complex class II: Preference for the golden mean. Molecular Ecology 28(23): 5133-5144. doi: 10.1111/mec.15273. The article is included in the thesis. Also available at: https://doi.org/10.1111/mec.15273 |
Paper III: Rekdal SL, Anmarkrud JA, Lifjeld JT and Johnsen A. Elevated PHA-response at an intermediate number of major histocompatibility complex class II alleles in bluethroat nestlings. Manuscript prepared for submission to Biology Letters. To be published. The paper is not available in DUO awaiting publishing. |
Paper IV: Rekdal SL, Anmarkrud JA, Kleven O, Lifjeld JT and Johnsen A. Is extra-pair mating associated with the hypervariable major histocompatibility complex class I in willow warblers? Manuscript. To be published. The paper is not available in DUO awaiting publishing. |