Inbreeding and outbreeding depression in the white-footed mouse, Peromyscus leucopus, and the role of kin recognition and dispersal in minimizing these costs

Brian Keane, Purdue University

Abstract

There is an ample body of literature suggesting that the degree of genetic similarity between mates should affect their reproductive success. The reproductive success of matings between individuals that are very similar genetically may be low due to the problems associated with inbreeding while that for mates that are very dissimilar genetically may be low due to outbreeding depression. In this study I have attempted to measure the cost of inbreeding and outbreeding in a natural population of the white-footed mouse, Peromyscus leucopus. The importance of kin recognition and dispersal as mechanisms for minimizing these costs was also examined. The degree of genetic similarity between mates had a significant effect on reproductive success. By breeding pairs of mice over a wide range of degrees of genetic similarity in a laboratory colony, a significant inbreeding depression in litter size at weaning and mean offspring weight at weaning was demonstrated as well as a significant outbreeding depression in mean offspring weight at weaning. In this population, matings between individuals of an intermediate degree of relatedness (first cousins) resulted in the highest reproductive success. Kin recognition appears to be an important mechanism for reducing the costs of extreme inbreeding and outbreeding in P. leucopus. In an arena, estrous females presented with odors from males of several different degrees of relatedness showed a significant preference for first cousins. When presented with actual males, estrous females again showed a significant preference for first cousins. Nonestrous females showed no such preferences. Dispersal was very localized in this population; this makes extreme outbreeding unlikely but suggests the potential for inbreeding. Matings between individuals whose origins were separated by different geographic distances (adjacent home ranges - different populations) showed no evidence of inbreeding depression and possibly a slight outbreeding depression. Such a result suggests that the short distance male biased dispersal in association with the high adult turnover rate, small litter sizes, and high juvenile mortality is sufficient to make it unlikely that opposite-sex close kin occupy overlapping home ranges as adults.

Degree

Ph.D.

Advisors

Waser, Purdue University.

Subject Area

Biology

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