Ellen D . Ketterson

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When selection on males and females differs, the sexes may diverge in phenotype. Hormones serve as a proximate regulator of sex differences by mediating sex-biased trait expression. To integrate these perspectives, we consider how suites of traits mediated by the same hormone in both sexes might respond to selection. In male birds, plasma testosterone (T)(More)
-This article, which focuses on hormones and the diverse effects they have on behavior and physiology, raises evolutionary questions that hormonal studies appear especially well suited to address. These include the endocrine basis for life-history trade-offs, the role of hormones in adaptive alterations in social organization and mating systems, and whether(More)
Monogamous male birds typically allocate less e¡ort to courtship and more to parental behaviour than males of polygynous species. The seasonal pattern of testosterone (T) secretion varies accordingly. Monogamous males exhibit a spring peak in plasmaT followed by lower levels during the parental phase, while males of polygynous species continue to court(More)
Understanding physiological and behavioral mechanisms underlying the diversity of observed life-history strategies is challenging because of difficulties in obtaining long-term measures of fitness and in relating fitness to these mechanisms. We evaluated effects of experimentally elevated testosterone on male fitness in a population of dark-eyed juncos(More)
The past 30 years of immunological research have revealed much about the proximate mechanisms of maternal antibody transmission and utilization, but have not adequately addressed how these issues are related to evolutionary and ecological theory. Much remains to be learned about individual differences within a species in maternal antibody transmission as(More)
Hormones coordinate the co-expression of behavioral, physiological, and morphological traits, giving rise to correlations among traits and organisms whose parts work well together. This article considers the implications of these hormonal correlations with respect to the evolution of hormone-mediated traits. Such traits can evolve owing to changes in(More)
Monogamous and polygynous male songbirds generally differ in their breeding season profiles of circulating testosterone. Testosterone level spikes early in the breeding season of monogamists and then declines, but it remains high in polygynists. Male dark-eyed juncos (Junco hyemalis) are socially monogamous and exhibit the usual pattern, but experimental(More)
When a trait's effect on fitness depends on its interaction with other traits, the resultant selection is correlational and may lead to the integration of functionally related traits. In relation to sexual selection, when an ornamental trait interacts with phenotypic quality to determine mating success, correlational sexual selection should generate genetic(More)