Examining the genetic and phenotypic correlation between survival and fecundity in a wild bird
There is intraspecific variation in reproduction and survival, which has been hypothesised to be the result of trade-offs in investment. However, we lack compelling evidence that trade- offs drive variation within species, perhaps because genetic trade-offs are masked by environmental variation. We used a long-term dataset of breeding records for a closed population of house sparrows (Passer domesticus) and its associated pedigree to separate the genetic and environmental covariance between fecundity and survival. We measured age-specific changes in reproductive outputs and estimated the heritability of both offspring production and survival in multivariate animal models. Our results show no evidence for survival costs to reproductive output. Nor did we find evidence that individuals fecundity and survival are correlated either the genetic or permanent environment level. Our findings show no evidence that variation in fecundity is driven by the offspring-production/survival trade-off. Instead, our results show that individuals are only somewhat consistent in their reproductive output, and suggest this is a possible mechanism why selection cannot act on individual quality.