Insulin-like growth factor 1 and life-history evolution of passerine birds

1. Natural selection has generated a diversity of ways in which vertebrates allocate their resources between fundamental life-history traits. The availability of possible evolutionary trajectories of these traits is limited by various genetic, physiological, and phylogenetic constraints. This causes trade-offs due to shared resource pools for, or genetic linkage of, competing traits. The majority of these trade-offs are mediated by hormones and create the variability of phenotypes that can be observed in nature.
2. Insulin-like growth factor 1 (IGF-1) is an evolutionarily conserved peptide, which has been shown to be essential in the regulation of body size, the pattern of reproductive investment and lifespan across a broad taxonomic range of model species in laboratory and domesticated conditions. However, studies addressing corresponding evolutionary hypotheses on a broader scale and in free-living vertebrates are very rare.
3. In this phylogenetic comparative study on free-living p...