HERITABILITY OF FITNESS COMPONENTS IN A WILD BIRD POPULATION

Consistently with the prediction that selection should deplete additive genetic variance ( V_A ) in fitness, traits closely associated to fitness have been shown to exhibit low heritabilities ( h ²= V_A /( V_A + V_R )). However, empirical data from the wild indicate that this is in fact due to increased residual variance ( V_R ), rather than due to decreased additive genetic variance, but the studies in this topic are still rare. We investigated relationships between trait heritabilities, additive genetic variances, and traits' contribution to lifetime reproductive success (≈fitness) in a red-billed gull ( Larus novaehollandiae ) population making use of animal model analyses as applied to 15 female and 13 male traits. We found that the traits closely associated with fitness tended to have lower heritabilities than traits less closely associated with fitness. However, in contrast with the results of earlier studies in the wild, the low heritability of the fitness-related traits was not only due to their high residual variance, but also due to their low additive genetic variance. Permanent environment effects—integrating environmental effects experienced in early life as well as nonadditive genetic effects—on many traits were large, but unrelated to traits' importance for fitness.