Details
- Autor(en) / Beteiligte
- Titel
- Male ornaments, extra-pair mating, and immunocompetence in the common yellowthroat
- Ort / Verlag
- ProQuest Dissertations & Theses
- Erscheinungsjahr
- 2006
- Link zum Volltext
- Quelle
- ProQuest Dissertations & Theses A&I
- Beschreibungen/Notizen
- Sexual selection theory predicts that, within a species, males with larger secondary sexual traits are of higher genetic quality than less ornamented individuals. Females may benefit indirectly by mating with more ornamented males as they may receive higher quality genes for their offspring. Females constrained in their social mate choice to a less ornamented male may pursue extra-pair matings with males bearing larger ornaments in order to improve the genotypes of their offspring. Recent theoretical and experimental work suggests that the genetic benefits to the female may be in the form of genes for enhanced immune system function. I measured the T-cell mediated immune response of nestlings from mixed paternity broods to examine the hypothesis that females engage in extra-pair mating to gain genes for better immune system function for their offspring. Secondly, I quantified both cell-mediated and humoral immunity and health status of adult males to investigate whether male ornaments (male mask and bib size, and bib color) function as signals of genes for enhanced immune system function. In this second study I also investigated what role testosterone may play in mediating the relationship between male ornaments and immunity, as androgens like testosterone have been shown to simultaneously inhibit the immune system while being necessary for the development of secondary sexual traits in some species. Extra-pair paternity had a positive effect upon nestling T-cell mediated immune response, both between maternal half-sibling and paternal half-sibling comparisons. However, this effect was influenced by variation in temperature, with no difference between within-pair and extra-pair young in the warmer of two years. Male mask size was related positively to our measure of humoral immunity but not to our measurements of cell-mediated immunity or health. Neither bib size nor color was related to our immune and health parameters. Lastly, naturally occurring levels of testosterone had no observable effect upon male ornaments or health and immunity, and thus may not mediate the relationship between male mask size and humoral immunity.