Additive genetic variance and effects of inbreeding, sex and age on heterophil to lymphocyte ratio in song sparrows

1. Physiological traits can influence individual fitness and evolutionary changes in stress-related physiological traits have been hypothesized to mediate the evolution of life-history traits and trade-offs. The hypothesis that such physiological variation could drive ongoing life-history evolution requires non-zero additive genetic variance in individual stress-related physiological traits. However, the magnitude of genetic and environmental components of phenotypic variation in stress-related physiological traits has not been estimated in fully developed vertebrates under natural environmental conditions. 2. We used 490 observations of heterophil to lymphocyte (H:L) ratio, one stress-related physiological trait, collected from 350 fully developed song sparrows (Melospiza melodia) across nine different sampling periods to estimate direct and interacting effects of individual and parental coefficients of inbreeding (f), sampling period, age and sex, and to estimate additive genetic vari...