A complex mechanism translating variation of a simple genetic architecture into alternative life histories.

Understanding the processes that link genotype to phenotype is a central challenge in biology. Despite progress in discovering genes associated with ecologically relevant traits, a poor understanding of the processes and functions via which molecules mediate evolutionary differences leaves us critically far from linking proximate and ultimate causes of evolution. This knowledge gap is particularly large in multifaceted phenotypes of ecological relevance such as life histories where multiple traits covary and influence fitness.

Seasonal and genetic effects on lipid profiles of juvenile Atlantic salmon.

Seasonality can influence many physiological traits requiring optimal energetic capacity for life-history stage transitions. In Atlantic salmon, high-energy status is essential for the initiation of maturation. Earlier studies have linked a genomic region encoding vgll3 to maturation age, potentially mediated via body condition.

Understanding and applying biological resilience, from genes to ecosystems.

The natural world is under unprecedented and accelerating pressure. Much work on understanding resilience to local and global environmental change has, so far, focussed on ecosystems. However, understanding a system's behaviour requires knowledge of its component parts and their interactions.

Sex-specific overdominance at the maturation vgll3 gene for reproductive fitness in wild Atlantic salmon.

Linking reproductive fitness with adaptive traits at the genomic level can shed light on the mechanisms that produce and maintain sex-specific selection. Here, we construct a multigenerational pedigree to investigate sex-specific selection on a maturation gene, vgll3, in a wild Atlantic salmon population. The vgll3 locus is responsible for ~40% of the variation in maturation (sea age at first reproduction).

Sex-specific associations of the maturation locus with exploratory behavior and boldness in Atlantic salmon juveniles.

Studies linking genetics, behavior and life history in any species are rare. In Atlantic salmon (), age at maturity is a key life-history trait and associates strongly with the locus, whereby the vgll3* allele is linked with younger age at maturity, and higher body condition than the allele. However, the relationship between this genetic variation and behaviors like boldness and exploration which may impact growth and reproductive strategies is poorly understood.

Selection among critically endangered landlocked salmon ( m. ) families in survival and growth traits across early life stages and in different environments.

Endangered wild fish populations are commonly supported by hatchery propagation. However, hatchery-reared fish experience very different selective pressures compared to their wild counterparts, potentially causing genotype-by-environment interactions (G × E) in essential fitness traits. We experimentally studied early selection in a critically endangered landlocked Atlantic salmon population, first from fertilization to the swim-up stage in a common hatchery setting, and thereafter until the age of 5 months in two contrasting rearing environments.

Temporal allele frequency changes in large-effect loci reveal potential fishing impacts on salmon life-history diversity.

Fishing has the potential to influence the life-history traits of exploited populations. However, our understanding of how fisheries can induce evolutionary genetic changes remains incomplete. The discovery of large-effect loci linked with ecologically important life-history traits, such as age at maturity in Atlantic salmon (), provides an opportunity to study the impacts of temporally varying fishing pressures on these traits.

Monitoring of species' genetic diversity in Europe varies greatly and overlooks potential climate change impacts.

Genetic monitoring of populations currently attracts interest in the context of the Convention on Biological Diversity but needs long-term planning and investments. However, genetic diversity has been largely neglected in biodiversity monitoring, and when addressed, it is treated separately, detached from other conservation issues, such as habitat alteration due to climate change. We report an accounting of efforts to monitor population genetic diversity in Europe (genetic monitoring effort, GME), the evaluation of which can help guide future capacity building and collaboration towards areas most in need of expanded monitoring.

Tissue-specific metabolic enzyme levels covary with whole-animal metabolic rates and life-history loci via epistatic effects.

Metabolic rates, including standard (SMR) and maximum (MMR) metabolic rate have often been linked with life-history strategies. Variation in context- and tissue-level metabolism underlying SMR and MMR may thus provide a physiological basis for life-history variation. This raises a hypothesis that tissue-specific metabolism covaries with whole-animal metabolic rates and is genetically linked to life history.

Genotype-specific variation in seasonal body condition at a large-effect maturation locus.

Organisms use resource allocation strategies to survive seasonal environmental changes and life-history stage transitions. Earlier studies found a transcription cofactor, v associating with maturation timing that inhibits adipogenesis in mice and affects body condition in juvenile salmon. Owing to a lack of temporal studies examining seasonality effects on phenotypes such as genotype, body condition, maturation and different life stages, we investigated the influence of different larval and juvenile temperatures, genotype and interactions with body condition and maturation rate.

Atlantic salmon () age at maturity is strongly affected by temperature, population and age-at-maturity genotype.

Age at maturity is a key life history trait involving a trade-off between survival risk and reproductive investment, and is an important factor for population structures. In ectotherms, a warming environment may have a dramatic influence on development and life history, but this influence may differ between populations. While an increasing number of studies have examined population-dependent reactions with temperature, few have investigated this in the context of maturation timing.

Sulphonamide inhibition studies of the β-carbonic anhydrase GsaCAβ present in the salmon platyhelminth parasite .

A β-class carbonic anhydrase (CA, EC 4.2.1.

The effect of temperature and dietary energy content on female maturation and egg nutritional content in Atlantic salmon.

The environment experienced by a female influences reproductive traits in many species of fish. Environmental factors such as temperature and diet are not only important mediators of female maturation and reproduction but also of egg traits and offspring fitness through maternal provisioning. In this study, we use 3-year-old tank-reared Atlantic salmon from two Finnish populations to investigate the effect of temperature and diet on maturation and egg traits.

Dissecting the loci underlying maturation timing in Atlantic salmon using haplotype and multi-SNP based association methods.

Characterizing the role of different mutational effect sizes in the evolution of fitness-related traits has been a major goal in evolutionary biology for a century. Such characterization in a diversity of systems, both model and non-model, will help to understand the genetic processes underlying fitness variation. However, well-characterized genetic architectures of such traits in wild populations remain uncommon.

A pituitary gene network linking vgll3 to regulators of sexual maturation in male Atlantic salmon.

Age at maturity is a key life history trait and a significant contributor to life history strategy variation. The maturation process is influenced by genetic and environmental factors, but specific causes of variation in maturation timing remain elusive. In many species, the increase in the regulatory gonadotropin-releasing hormone 1 (GnRH1) marks the onset of puberty.

Host Developmental Stage Effects on Parasite Resistance and Tolerance.

AbstractHosts can defend themselves against parasites either by preventing or limiting infections (resistance) or by limiting parasite-induced damage (tolerance). However, it remains underexplored how these defense types vary over host development with shifting patterns of resource allocation priorities. Here, we studied the role played by developmental stage in resistance and tolerance in Atlantic salmon ().

Life-history genotype explains variation in migration activity in Atlantic salmon ().

One of the most well-known life-history continuums is the fast-slow axis, where 'fast' individuals mature earlier than 'slow' individuals. 'Fast' individuals are predicted to be more active than 'slow' individuals because high activity is required to maintain a fast life-history strategy. Recent meta-analyses revealed mixed evidence for such integration.

Cloning, purification, kinetic and anion inhibition studies of a recombinant β-carbonic anhydrase from the Atlantic salmon parasite platyhelminth .

A β-class carbonic anhydrase (CA, EC 4.2.1.

Strong regulatory effects of vgll3 genotype on reproductive axis gene expression in juvenile male Atlantic salmon.

Age at maturity is a major contributor to the diversity of life history strategies in organisms. The process of maturation is influenced by both genetics and the environment, and includes changes in levels of sex hormones and behavior, but the specific factors leading to variation in maturation timing are poorly understood. gnrh1 regulates the transcription of gonadotropin genes at pubertal onset in many species, but this gene is lacking in certain teleost species including Atlantic salmon (Salmo salar), which raises the possibility of the involvement of other important regulatory factors during this process.

Linking vgll3 genotype and aggressive behaviour in juvenile Atlantic salmon (Salmo salar).

We tested the possibility that vgll3, a gene linked with maturation age in Atlantic salmon (Salmo salar), may be associated with behaviour by measuring aggressiveness and feeding activity in 380 juveniles with different vgll3 genotypes. Contrary to our prediction, individuals with the genotype associated with later maturation (vgll3*LL) were significantly more aggressive than individuals with the genotype associated with earlier maturation (vgll3*EE). Individuals with higher aggression were also significantly lighter in colour and had higher feeding activity.

Standard metabolic rate does not associate with age-at-maturity genotype in juvenile Atlantic salmon.

Atlantic salmon () is a species with diverse life-history strategies, to which the timing of maturation contributes considerably. Recently, the genome region including the gene  has gained attention as a locus with a large effect on Atlantic salmon maturation timing, and recent studies on the  locus in salmon have indicated that its effect might be mediated through body condition and accumulation of adipose tissue. However, the cellular and physiological pathways leading from  genotype to phenotype are still unknown.

Genetic coupling of life-history and aerobic performance in Atlantic salmon.

A better understanding of the genetic and phenotypic architecture underlying life-history variation is a longstanding aim in biology. Theories suggest energy metabolism determines life-history variation by modulating resource acquisition and allocation trade-offs, but the genetic underpinnings of the relationship and its dependence on ecological conditions have rarely been demonstrated. The strong genetic determination of age-at-maturity by two unlinked genomic regions ( and ) makes Atlantic salmon () an ideal model to address these questions.

Major population splits coincide with episodes of rapid climate change in a forest-dependent bird.

Climate change influences population demography by altering patterns of gene flow and reproductive isolation. Direct mutation rates offer the possibility for accurate dating on the within-species level but are currently only available for a handful of vertebrate species. Here, we use the first directly estimated mutation rate in birds to study the evolutionary history of pied flycatchers ().

Refining the genomic location of single nucleotide polymorphism variation affecting Atlantic salmon maturation timing at a key large-effect locus.

Efforts to understand the genetic underpinnings of phenotypic variation are becoming more and more frequent in molecular ecology. Such efforts often lead to the identification of candidate regions showing signals of association and/or selection. These regions may contain multiple genes and therefore validation of which genes are actually responsible for the signal is required.