Sexual ornaments and immunocompetence in male ring-necked pheasants Phasianus colchicus
by Doll, Nicholas Damon, M.S., WESTERN ILLINOIS UNIVERSITY, 2010, 31 pages; 1480032

Abstract:

The Hamilton-Zuk hypothesis suggests male secondary sexual characteristics are honest signals of a male’s genetic disease resistance. Females may choose more ornamented males to gain indirect benefits such as increased fitness of their offspring. In this study, I compared the expression of phenotypic traits of male Ring-necked Pheasants (Phasianus colchicus) to the activity of their immune system based on two immune assays designed to test aspects of innate and acquired immunity. The purpose of this study was to determine if the phenotypic traits measured in this study accurately predicted a male pheasant’s ability to mount an immune response therefore indicating the male’s ability to provide disease resistance to the offspring. Innate immunity was determined from the results of a bacteria killing assay. I used whole blood samples from male pheasants plated on tryptic soy agar along with an Escherichia coli strain (ATCC #8739) and a nutrient media mix to test the blood’s ability to kill bacteria. I injected the patagium of the right wing of male pheasants with a solution of phytohemagglutinin (PHA) and measured the swelling produced to test the activity of the acquired immune system. I found the ultraviolet coloration of head feathers to be significantly correlated with innate immunity. This is the first study to suggest ultraviolet reflectance is an honest indicator of immunocompetence in male pheasants. Also, I found that male pheasant body condition was positively related to acquired immunity and wattle redness was positively correlated to body condition suggesting a direct role for body condition and an indirect role for wattle redness as honest indicators of immunocompetence. The two immunocompetence assays performed in this study were not significantly correlated with each other and each was correlated with different phenotypic traits. This suggests pheasant ornaments may signal multiple aspects of immune function, providing support for the multiple message hypothesis. These results may also indicate support for the redundant signal hypothesis because the use of several ornaments may be a better indicator of a males overall health than just one of these ornaments.

 
AdviserBrian D. Peer
SchoolWESTERN ILLINOIS UNIVERSITY
SourceMAI/ 49-01, p. , Sep 2010
Source TypeThesis
SubjectsEcology; Microbiology; Zoology
Publication Number1480032
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