| Summary: | Papers number 1, 3, 4, 5 and 6 of the thesis are not available in Munin: 1. Figenschou, L., Folstad, I. & Liljedal, S.: «Lek fidelity of male Arctic charr», Canadian Journal of Zoology, 82(2004): 1278-1284 (National Research Council Canada - publisher's restrictions). Available at http://dx.doi.org/10.1139/z04-106 3. Rudolfsen, G., Figenschou, L., Folstad, I., Tveiten, H. & Figenschou, M.: «Rapid adjustments of sperm characteristic in relation to social status», Proceedings of the Royal Society of London, Series B-Biological Sciences, 273(2006): 325-332 (publisher's restrictions). Available at http://dx.doi.org/10.1098/rspb.2005.3305 4. Figenschou, L., Rudolfsen, G., & Folstad, I.: «Female Arctic charr do not show apparent benefits from exposing their eggs to sperm from dominant males», Journal of Fish Biology, 71(2007): 284–289 (Wiley - publisher's restrictions). Available at http://dx.doi.org/10.1111/j.1095-8649.2007.01477.x 5. Figenschou, L., Skau, P.A., Folstad, I., Rudolfsen, G., Hanssen, S.A., Kortet, R., Killie, J.E., Oskam, I. & Strand, H.: «Parasite intensities and male social status as modifiers of sperm production and sperm swimming speed in the Arctic charr (Salvelinus alpinus)» (manuscript) 6. Figenschou, L., Skau, P.A., Folstad, I., Rudolfsen, G., Hanssen, S.A., Kortet, R., Killie, J.E. & Strand, H.: «Immune activation leads to reproductive compensation in Arctic charr (Salvelinus alpinus)» (manuscript) This thesis illuminates several aspects of mate choice and sexual selection in a species with external fertilization and no parental care. At a general level we have contributed to the basic framework within evolutionary biology and ecology and at a more specific level, as the proximate mechanisms controlling the associations between immune response, parasite intensities and traits indicative of sperm quality are not straightforward, we examined the effect of increased immunological activity on sperm traits. Our results have established the significance of male social status, and in the two inter-disciplinary studies, showed that parasitized and infected males seem to invest more in sperm quality, less in ornamental development and adapt to sperm competition (i.e., subordinate mating tactic). Thus, as reproductive decisions in charr seem to be strongly influenced by parasites and antigens, host parasite co-evolution may have been a significant mechanism in the maintenance and evolution of both male sexual behaviour and ornamentation.
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