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Phenotypic correlations among relatives and variability in reproductive performance in populations of the vole Micortus townsendii Anderson, Judith L.


The purpose of this study was to investigate the potential of a population of voles (Microtus townsendii) to respond genetically to natural selection upon ecologically important traits. Reproductive performance of individual voles was observed in small outdoor enclosures, and their offspring were monitored after release into natural populations. Among the possible factors influencing success of litters, maternal behavior proved to be an important determinant of litter size at recruitment. A measure of the contribution by individual parents to the next generation's gene pool revealed a serious reduction in effective numbers between July and September for this population. Heritability analysis was performed on the following traits: juvenile growth rate, maximum body size, tendency to breed in winter, age at puberty, tendency to leave a population, activity, and agonistic behavior. None of these traits manifested a strong genetic influence. However, correlations between offspring and mothers were significant for maximum size, activity, and agonistic behavior, and there was evidence that common environment effects tend to make siblings resemble one another in juvenile growth rate, age at puberty, and dispersal tendency.

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