The quantitative genetics of fitness in a wild seabird

Additive genetic variance in fitness is a prerequisite for adaptive
evolution, as a trait must be genetically correlated with fitness to
evolve. Despite its relevance, additive genetic variance in fitness has
not often been estimated in nature. Here, we investigate additive genetic
variance in lifetime and annual fitness components in common terns (Sterna
hirundo). Using 28 years of data comprising ca. 6000 pedigreed
individuals, we find that additive genetic variances in the Zero-inflated
and Poisson components of lifetime fitness were effectively zero, but
estimated with high uncertainty. Similarly, additive genetic variances in
adult annual reproductive success and survival did not differ from zero,
but were again associated with high uncertainty. Simulations suggested
that we would be able to detect additive genetic variances as low as 0.05
for the Zero-inflated component of fitness, but not for the Poisson
component, for which adequate statistical power would require c. two more
decades (four tern generations) of data collection. As such, our study
suggests heritable variance in common tern fitness to be rather low if not
zero, shows how studying the quantitative genetics of fitness in natural
populations remains challenging, and highlights the importance of
maintaining long-term individual-based studies of natural populations.