| Summary: | ii, 75 leaves : illustrations (some colour), map 29 cm Includes abstract. Includes bibliographical references (leaves 62-68). Although mating systems are generally considered fixed properties of species, ecological factors can play an important role in the degree to which sexual selection acts on mating related traits in a population. Differences in the distribution of individuals can result in variation in sexually-selected traits. I explored the influence of ecological factors on population distribution and sexually-selected traits within and among four genetically isolated populations of brook trout in Cape Race, Newfoundland. Generally, females aggregate in areas with abiotic conditions that are optimal for offspring survival. Relationships between population density, sex ratio, and phenotypic variation suggest that social environment plays a large role in the distribution of brook trout within streams, as well as variation in the direction and magnitude of sexual size and colour dimorphism. Although these general trends were observed, variation among streams suggests that different factors are influencing the degree to which sexual selection operates on Cape Race.
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