This Friday, 28.2 at 12, Paul Bangura will defend his PhD thesis “Links between large-effect life-history loci and behavior in juvenile Atlantic salmon”. The electronic version of the thesis can be viewed at https://helda.helsinki.fi/items/d6ab37b9-1ce5-41bc-add9-9b711c419bb5
Understanding the links between genetic variation, behavior and life-history traits, such as age at maturation is an important research theme in biology. Behaviors such as aggression, boldness, and exploration are critical for survival and resource acquisition, and can significantly impact maturation timing and overall fitness. Recent advances in genomics have identified large-effect loci, such as vgll3 and six6, which are associated with age-at-maturity in Atlantic salmon (Salmo salar), but prior to my thesis research, their potential influence on key behavioral traits was unknown. In this thesis, I investigated the association between vgll3 and six6 genotypes and behavior in juvenile Atlantic salmon, focusing on traits that are connected with survival and fitness. For both loci, E and L refer to the alleles associated with early and late maturation, respectively. Examining whether these loci influence aggression, boldness, and exploration, enabled investigating the genetic mechanisms underlying behaviorally mediated life-history strategies. Juvenile Atlantic salmon from controlled hatchery cohorts with known vgll3 and six6 genotypes were observed in experiments to assess how genetic variation at these large-effect loci affects behavioral expression, potentially indirectly linking these behaviors to fitness outcomes and maturation timing. First, I analyzed aggression among juveniles with differing vgll3 genotypes and found that vgll3*LL individuals displayed significantly higher aggression than vgll3*EE individuals. Aggression is a crucial behavior in the context of competition for resources, and elevated aggression may confer advantages in growth and dominance, ultimately influencing maturation, age, and fitness. However, contrary to our predictions, increased aggression and proactive behaviors were observed in vgll3*LL rather than vgll3*EE fish. This may lead to delayed maturation in vgll3*LL individuals due to higher energy use. Second, boldness and exploration were assessed through novel environment and object tests, revealing that, and also contrary to our initial predictions, vgll3*LL juveniles exhibited greater boldness and exploratory behavior than their vgll3*EE counterparts. These proactive behaviors likely come at an energetic cost, further supporting the notion that delayed maturation in vgll3*LL individuals may be a consequence of increased energy expenditure early in life. While six6 did not show a strong direct link with these behaviors, significant behavioral differences between the sexes and with respect to food availability underscore the multifaceted role of both genetic and ecological factors in shaping fitness-related traits. Overall, this thesis identified several associations between behavior and large-effect life-history loci further highlighting the pleiotropic effects of these loci on diverse phenotypic traits. The findings of this thesis underscore the value of integrating behavioral and genetics research by demonstrating how genomic approaches can reveal the underpinnings of behavioral diversity, thereby offering a clearer understanding of the ecological and evolutionary factors contributing to life-history diversity in Atlantic salmon.
The public examination will take place in the Ilves lecture room at Lammi Biological Station, Pääjärventie 320, Lammi, Finland.
Associate Professor Marie-Jeanne Perrot-Minnot, Université de Bourgogne, France, will serve as the opponent.
Welcome!