| Summary: | Understanding the underlying causes of variation in life history traits, both genetic and environmental, is an instrumental foundation to understanding and predicting how species and populations change in response to environmental and anthropogenic influences. In this thesis, I have studied the functions and consequences of the gene vgll3, which in Atlantic salmon (Salmo salar) has a strong association with age at maturity. Through experimental studies, and under different environmental contexts, I have explored the function of vgll3 in Atlantic salmon by measuring gene expression, metabolic traits, and maturation rates. Gene expression in gonads was dependent on age, sex, and season. Here, our results suggested that expression of vgll3 may have an inhibiting effect on early stages of gonadal maturation in both males and females, but that the gene may play different roles at later stages of maturation dependent on sex. Maximum metabolic rate was higher for young individuals with the late-maturation vgll3 genotype, but there was no association between genotype and standard metabolic rate. This suggested that the effect of vgll3 on the maturation process is likely not mediated by effects on maintenance metabolism, but that the effect may have a connection with differences in aerobic scope. Further, this indicated a potential for linked selection on aerobic scope and age at maturity. The relative effect of vgll3 genotype on rates of maturation was not affected by rearing temperature or population of origin, but inherent differences in rates of maturation between these factors resulted in different absolute effects of vgll3 genotype. Additionally, we found that the effect of temperature on maturation rate was different between the study's two populations of origin. In summary, we have discovered multiple aspects of how this life history gene affects sexual maturation and how its function can vary between various contexts. In addition to developing our understanding of the mechanistic background for the influence of ...
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