Document Type



Master of Science



Date of Defense


Graduate Advisor

Patricia G. Parker, Ph.D.


James Hunt, Ph.D.


Robert Marquis, Ph.D.

Zuleyma Tang-Martinez, Ph.D.


Inbreeding depression should select for the ability of females to avoid inbreeding or minimize its effects. We tested for a relationship between genetic similarity of social pairs and the occurrence of extra-pair fertilization (EPF) in the Mexican jay (Aphelocoma ultramarina), a bird species with known inbreeding depression and a high EPF rate (Brown and Brown 1998, Li and Brown 2000). Multi-locus minisatellite and microsatellite DNA fingerprinting were used to detect extra-pair young and measure genetic similarity between social parents. We found that 15 of 38 (39%) nests had at least one EPF and 21 of 115 (18%) young were the result of EPF. The mean DNA fingerprinting band-sharing score between social mates who had at least one EPF was significantly higher than the mean band-sharing score between mates who did not (0.35 vs. 0.26). The mean band-sharing score for non-EPF dyads (0.26) was similar to the background band sharing among non-relatives (0.23). The mean band sharing score for mates that had an EPF was significantly higher than that of non-relatives (background) and was significantly lower than that of half-siblings (0.51). Our results showed a significant positive relationship between genetic similarity of social mates and incidence of EPF at P<0.01.

OCLC Number