Abstract
Testosterone is an important hormone that has been shown to have sex-specific links to fitness in numerous species. Although testosterone concentrations vary substantially between individuals in a population, little is known about its heritable genetic basis or between-sex genetic correlations that determine its evolutionary potential. We found circulating neonatal testosterone levels to be both heritable (0.160 ± 0.064 s.e.) and correlated between the sexes (0.942 ± 0.648 s.e.) in wild red deer calves (Cervus elaphus). This may have important evolutionary implications if, as in adults, the sexes have divergent optima for circulating testosterone levels.
Highlights
Hormone concentrations vary between individuals in a population [1]; the causes of this variation remain poorly understood despite many hormones being important in mediating fitness-related traits [2,3,4]
Evidence suggests that testosterone levels are heritable in humans and captive populations of several taxa, but levels of genetic variance for testosterone concentration have rarely been investigated in the wild, where heritability estimates might be lower because individuals are subjected to greater environmental variation [8]
Most studies focus on adult concentrations despite substantial age-related variation in heritability estimates in humans
Summary
Hormone concentrations vary between individuals in a population [1]; the causes of this variation remain poorly understood despite many hormones being important in mediating fitness-related traits [2,3,4]. Most studies of interindividual testosterone variation have focused on adults, early-life concentrations may be important for juvenile fitness [6,7]. Most studies focus on adult concentrations despite substantial age-related variation in heritability estimates in humans (electronic supplementary material, table S1). Such studies tend to estimate heritability using traditional methods that rely on paired-relative relationships such as parent– offspring; these risk inflating heritability estimates due to shared environmental/maternal effects [9]. ‘Animal models’ allow the use of relatedness information across complex pedigrees, which both reduces the potential for bias and allows more efficient use of the data typical of natural populations (see [9,10] and references therein)
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