Biology subjects

Aykanat, T.

Publications and source records attributed to Aykanat, T..

At least 19 recordsLinked to original sources

bioRxiv2025

Interaction of two tightly linked loci in an adaptive genomic hotspot explains exploration behavior in juvenile Atlantic salmon in freshwater.

O_LIThe traits that are important for adaptation may exhibit genetic correlation due to pleiotropy or as a result of linkage. Understanding the genetic architecture of such correlations is important for predicting the selection response of populations. Exploration in fishes is a behavioral trait by which individuals may find habitats with better foraging and growth opportunities that subsequently improve their fitness. For example, in Atlantic salmon (Salmo salar), all individuals originate in spawning rivers where females lay eggs, but some juveniles migrate to small tributaries which are not spawning areas but provide favorable habitat patches for young salmon. The increased growth in these nursery streams may facilitate earlier sexual maturation, implying a potential correlation between exploration and maturation traits. C_LIO_LIIn this study, by sampling juveniles from two wild populations in the large Teno River catchment in northernmost Fennoscandia, we tested the genetic association between exploration behavior with nursery streams across four SNPs that span a 70-kb long genomic region with a major effect on age at maturity variation. Three of these SNPs are missense mutations in the vgll3 and akap11 genes, and one SNP tags a putative regulatory region with the strongest association with the age-at-maturity trait. C_LIO_LIWe show that the exploration behavior was linked to the genomic region in one of the two studied populations. However, the genetic association was substantial in the missense SNP located in the akap11 gene, which is farthest away from the vgll3 SNPs and previously ruled out as being linked to the age at maturity. We also detected a marginal interaction effect between SNPs in the vgll3 gene and akap11, indicating a potentially complex genetic architecture underlying the trait variation. C_LIO_LIOur results suggest that exploration and age at maturity are co-inherited within the same haplotype block, but we find no evidence for direct causality. These two traits may form a co-adapted trait complex that may be instrumental in local adaptation processes. C_LI

ecology↗

bioRxiv2025

Density-dependent expression of epitranscriptomic, stress, and appetite regulating genes in Atlantic salmon

Intraspecific competition due to e.g., density, has substantial influence on fitness dynamics and life histories, but the underlying physiological mechanisms are often complex, and the molecular basis unclear. Further, designing laboratory experiments to measure physiological responses that reflect natural conditions is challenging. Here, we reared Atlantic salmon juveniles in semi-wild conditions in two naturally occurring densities to investigate the molecular mechanism of density-related changes in the hypothalamus, a key brain region regulating stress and energy homeostasis. We measured density-dependent changes in the expression of 12 genes involved in appetite and stress regulation, and 16 genes involved in post-transcriptional regulation of gene expression via m6A RNA methylation. This gene set includes paralog pairs, to account for potential functional divergence associated with salmonid genome duplication. We also quantified genotype-environment interactions between density and two major life-history loci, vgll3 and six6. We found significant density-related differences in the expression of genes coding for corticotropin-releasing factors, appetite stimulators and inhibitors, and m6A RNA methylation actors. Moreover, a paralogue of an appetite inhibitor showed a density-dependent pattern that was the opposite of what was expected. Six6 locus was also associated with changes in the expression of epitranscriptomic markers, including two writers and one eraser. Our results highlight that individuals response to density in natural conditions is shaped by a complex interplay between stress, appetite and epitranscriptomic pathways in the hypothalamus. In addition, the functional divergence of paralogs indicates a potential role of genome duplication shaping such a response. We emphasize the value of integrating different physiological responses at the molecular level to better understand ecological processes affected by environmental change.

molecular biology↗

bioRxiv2024

Large effect life-history genomic regions are associated with functional morphological traits in Atlantic salmon

Understanding pleiotropic architectures of phenotypes is instrumental for identifying the functional basis of adaptive genetic variation in the wild. Life-history variation may have a morphological basis that mediates resource acquisition allocation pathways, but identifying the underlying genetic basis of such traits is challenging. Using Atlantic salmon juveniles reared in common garden conditions, we test if two life-history associated loci in Atlantic salmon, six6 and vgll3, are also associated with functional morphological traits. These loci had previously shown to exhibit strong signals of adaptation and are highly correlated with sea age at maturity. We show that genetic variation at the vgll3 locus is linked to variation in morphological traits that underlie swimming performance, along a trade-off axis between efficient cruising and maneuvering, while the genetic variation at the six6 locus was linked to variation in body-head proportions suggesting the potential functional importance of these traits for resource acquisition efficiency. However, the direction of changes in morphological traits associated with late-vs. early-maturing alleles was not always consistent with the expected direction of an effect to maturation timing. Our results reveal a complex morphological landscape associated with the genetic variation in these loci, possibly as a result of pleiotropy or linkage across these genomic regions.

ecology↗

bioRxiv2024

Diet drives performance trade-offs along the ontogeny in the Atlantic salmon

Understanding the mechanistic basis of life history divergence is fundamental for predictive ecology. Variation in resource use impacts life history divergence and provides a framework for studying life history trade-offs. Contrary to the theory, empirical evidence does not support that resource allocation alone mediates life history divergence in the wild, which subsequently suggests a pivotal role for resource acquisition, but this has not been empirically demonstrated in free-living populations. Here, we sampled wild Atlantic salmon (Salmo salar) from different age groups during their marine feeding stage and hypothesized that prey taxa (crustaceans versus fish) have an age-dependent effect on the condition factor. We found that salmon in their first year at sea had a higher condition factor when foraging on larger numbers of crustaceans and a lower condition factor when foraging on larger numbers of fish, and vice versa in older sea age groups. Provided that condition factor is a predictor of age-at-maturity, our results show that resource acquisition may be an important process shaping life history variation in Atlantic salmon via modulating age-dependent performance trade-offs. Our results also emphasize the importance of bottom-up trophic cascades for maturation age and help to better predict the maturation dynamics of wild populations in the marine environment.

ecology↗

bioRxiv2024

Ontogenetic variation in the marine foraging of Atlantic salmon functionally links genomic diversity with a major life history polymorphism

The ecological role of heritable phenotypic variation in free-living populations remains largely unknown. Knowledge of the genetic basis of functional ecological processes can link genomic and phenotypic diversity, providing insight into polymorphism evolution and how populations respond to environmental changes. By quantifying the marine diet of Atlantic salmon, we assessed how foraging behavior changes along the ontogeny, and in relation to genetic variation in two loci with major effects on age at maturity (six6 and vgll3). We used a two-component, zero-inflated negative binomial model to simultaneously quantify foraging frequency and foraging outcome, separately for fish and crustaceans diets. We found that older salmon forage for both prey types more actively (as evidenced by increased foraging frequency), but with a decreased efficiency (as evidenced by fewer prey in the diet), suggesting an age-dependent shift in foraging dynamics. The vgll3 locus was linked to age-dependent changes in foraging behavior: younger salmon with vgll3LL (the genotype associated with late maturation) tended to forage crustaceans more often than those with vgll3EE (the genotype associated with early maturation), whereas the pattern was reversed in older salmon. Vgll3 LL genotype was also linked to a marginal increase in fish acquisition, especially in younger salmon, while six6 was not a factor explaining the diet variation. Our results suggest a functional role for marine feeding behavior linking genomic diversity at vgll3 with age at maturity among salmon, with potential age-dependent trade-offs maintaining the genetic variation. A shared genetic basis between dietary ecology and age at maturity likely subjects Atlantic salmon populations to evolution induced by bottom-up changes in marine productivity.

ecology↗

bioRxiv2024

Early survival in Atlantic salmon is associated with parental genotype at loci linked to timing of maturation late in life

Large effects loci often contain genes with critical developmental functions with potentially broad effects across life-stages. However, the life-stage-specific fitness consequences are rarely explored. In Atlantic salmon, variation in two large-effect loci, six6 and vgll3, is linked to age at maturity, and several physiological and behavioural traits in early life. By genotyping the progeny of wild Atlantic salmon that were planted into natural streams with nutrient manipulations, we tested if genetic variation in these loci is associated with survival in early life. We found that higher early life survival was linked to the genotype associated with late maturation in the vgll3, but with early maturation in the six6 locus. These effects were significant in high-nutrient, but not in in low-nutrient streams. The differences in early survival were not explained by additive genetic effects in the offspring generation, but by maternal genotypes in the six6 locus, and by both parents genotypes in the vgll3 locus. Our results suggest that indirect genetic effects by large-effect loci can be significant determinants of offspring fitness. This study demonstrates an intriguing case of how large-effect loci can exhibit complex fitness associations across life stages in the wild and indicates that predicting evolutionary dynamics is difficult.

evolutionary biology↗

bioRxiv2022

Adipose tissue mitochondrial respiration in Atlantic salmon: implications for sex-dependent life-history variation

Adipose tissue is essential for energy homeostasis, with mitochondria having a central role in its function. Mitochondria-mediated white adipose tissue dysfunction has been linked to several metabolic disorders in humans but surprisingly little is known about natural variation in mitochondrial function in wild animal populations, and its evolutionary significance. Early sexual maturation (low age-at-maturity) in Atlantic salmon (Salmo salar) is promoted by higher adiposity and has a strong genetic association with the vgll3 locus. This makes Atlantic salmon a convenient wild model to study the potential role of mitochondria-mediated adipose tissue processes in relation to the timing of maturation. Yet, mitochondrial respiration has not been measured in the adipose tissue in fish, and the lack of data is restricting the development of informed hypotheses. Here, using 13 Atlantic salmon individuals reared in common-garden conditions, we first verified the feasibility of measuring mitochondrial respiration in the adipose tissue. As expected, the respiration level was generally low, but nonetheless we successfully quantified its biological variation in the adipose tissue. Next, we analysed the potential association of mitochondrial respiration with mitochondrial DNA (mtDNA) content, adipocyte size, sex, and the vgll3 genotype. Despite low samples sizes, mitochondrial respiration, leak respiration, and coupling capacity (P/E ratio) were marginally significantly decreased in immature females carrying with the vgll3 early maturation compared to the alternative genotype. Based on these results, we suggested two new hypotheses on how the coupling capacity of oxidative phosphorylation could be linked with the timing of maturation via adiposity and pave the way to study the mechanistic relationships between life-history variation and mitochondrial bioenergetics in wild populations.

physiology↗

bioRxiv2022

Genetic stock identification reveals greater use of an oceanic feeding ground around the Faroe Islands by multi-sea winter Atlantic salmon.

There is a general paucity of knowledge regards spatial variation in marine resource use for many taxa, even those of high socio-economic importance such as Atlantic salmon. While it is known that the oceans around the Faroe Islands support a salmon feeding ground, the relative use of this feeding ground by different age classes across different stocks remains largely unexplored. Using a combination of genetic stock assignment and run-reconstruction models, we observed a consistent pattern whereby the proportion of multi-sea winter (MSW) salmon for a given reporting group was substantially greater around the Faroes than the MSW proportion for that reporting groups among the prefisheries abundance. Surprisingly, MSW fish from Ireland and UK were as likely to occur around the Faroes as were MSW fish from more north-eastern regions such as the Teno river and the Barents and White Seas. MSW fish from Southern Norway were the most likely to be caught at the Faroes. While 1SW salmon from Ireland and UK as well as from Southern Norway occurred at similar rates around the Faroes, 1SW fish from more north-eastern reporting groups were nearly entirely absent from the same feeding ground. In combination with previous studies that examine the marine distribution of Atlantic salmon, our results strongly indicate that the oceans around the Faroes play host to a predominantly MSW salmon feeding ground and that use of this resource varies both within the age classes of a given stock as well as between different stocks. Furthermore, these results suggest that MSW fish from certain stocks might preferentially undertake migrations to the Faroes. Variation in spatial resource use may help to buffer salmon stocks against localised negative changes in marine conditions.

ecology↗

bioRxiv2021

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

Atlantic salmon (Salmo salar) is a species with diverse life-history strategies, to which the timing of maturation contributes considerably. Recently, the genome region including the gene vgll3 has gained attention as a locus with a large effect on salmon maturation timing, and recent studies on the vgll3 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 vgll3 genotype to phenotype are still unknown. Standard metabolic rate is a potentially important trait for resource acquisition and assimilation and we hypothesized that this trait, being a proxy for the maintenance energy expenditure of an individual, could be an important link in the pathway from vgll3 genotype to maturation-timing phenotype. As a first step to studying links between vgll3 and the metabolic phenotype of Atlantic salmon, we measured the standard metabolic rate of 150 first year Atlantic salmon juveniles of both sexes, originating from 14 different families with either late maturing or early maturing vgll3 genotypes. No significant difference in mass-adjusted standard metabolic rate was detected between individuals with different vgll3 genotypes, indicating that juvenile salmon of different vgll3 genotypes have similar maintenance energy requirements in the experimental conditions used and that the effects of vgll3 on body condition and maturation are not strongly related to maintenance energy expenditure in either sex at this life stage. Summary statementWe show that vgll3, a gene known to have significant effects on Atlantic salmon (Salmo salar) life-history strategy, does not associate with standard metabolic rate in salmon juveniles.

genetics↗

bioRxiv2021

Genetic coupling of life-history and aerobic performance in juvenile 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 (vgll3 and six6) makes Atlantic salmon (Salmo salar) an ideal model to address these questions. Using more than 250 juveniles in common garden conditions, we quantified the covariation between metabolic phenotypes -standard and maximum metabolic rates (SMR and MMR), and aerobic scope (AS) - and the life-history genomic regions and tested if food availability modulates the relationships. We found that the early maturation genotype in vgll3 was associated with higher MMR and consequently AS. Additionally, MMR exhibited physiological epistasis; it was decreased when late maturation genotypes co-occurred in both genomic regions. Contrary to our expectation, the life-history genotypes had no effects on SMR. Further, food availability had no effect on the genetic covariation, suggesting a lack of genotype-by-environment interactions. Our results provide insights on the key organismal processes that link energy use at the juvenile-stage to age-at-maturity, indicating potential mechanisms by which metabolism and life-history can coevolve.

evolutionary biology↗

bioRxiv2021

Refining the genomic location of SNP 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. In Atlantic salmon (Salmo salar), a large-effect locus for maturation timing, an ecologically important trait, occurs in a genomic region including two genes, vgll3 and akap11, but data for clearly determining which of the genes (or both) contribute to the association have been lacking. Here, we take advantage of natural recombination events detected between the two candidate genes in a salmon broodstock to reduce linkage disequilibrium at the locus, and thus enabling delineation of the influence of variation at these two genes on maturation timing. By rearing 5895 males to maturation age, of which 81% had recombinant vgll3/akap11 allelic combinations, we found that vgll3 SNP variation was strongly associated with maturation timing, whereas there was little or no association between akap11 SNP variation and maturation timing. These findings provide strong evidence supporting vgll3 as the primary candidate gene in the chromosome 25 locus for influencing maturation timing. This will help guide future research for understanding the genetic processes controlling maturation timing. This also exemplifies the utility of natural recombinants to more precisely map causal variation underlying ecologically important phenotypic diversity.

genetics↗

bioRxiv2021

Evolution in salmon life-history induced by direct and indirect effects of fishing

Understanding the drivers of evolution is a fundamental aim in biology. However, identifying the evolutionary impacts of human activities, both direct and indirect, is challenging because of lack of temporal data and limited knowledge of the genetic basis of most traits1. Atlantic salmon is a species exposed to intense anthropogenic pressures during its anadromous life cycle2. Previous research has shown that salmon age at maturity has evolved towards earlier maturation over the last 40 years, with an 18% decrease3 in the allele associated with late maturation at the large-effect vgll3 locus4; but the drivers of this change remain unknown. Here, we link genetic and phenotypic changes in a large Atlantic salmon population with salmon prey species biomass in the Barents Sea, temperature, and fishing effort in order to identify drivers of age at maturity evolution. We show that age at maturity evolution is associated with two different types of fisheries induced evolution acting in opposing directions: an indirect effect linked with commercial harvest of a salmon prey species (capelin) at sea (selection against late maturation), and a direct effect due to temporal changes in net fishing pressure in the river (surprisingly, selection against early maturation). Although the potential for direct and indirect evolutionary effects of fishing have been acknowledged, empirical evidence for induced changes at the genetic level has been lacking5. As capelin are primarily harvested to produce fish meal and oil for aquaculture6, we hereby identify an indirect path by which Atlantic salmon aquaculture may negatively affect wild populations.

evolutionary biology↗

bioRxiv2020

Heterogeneous genetic basis of age at maturity in salmonid fishes

Understanding the genetic basis of repeated evolution of the same phenotype across taxa is a fundamental aim in evolutionary biology and has applications to conservation and management. However, the extent to which interspecific life-history trait polymorphisms share evolutionary pathways remains under-explored. We address this gap by studying the genetic basis of a key life-history trait, age at maturity, in four species of Pacific salmon (genus Oncorhynchus) that exhibit intra- and interspecific variation in this trait - Chinook Salmon, Coho Salmon, Sockeye Salmon, and Steelhead Trout. We tested for associations in all four species between age at maturity and two genome regions, six6 and vgll3, that are strongly associated with the same trait in Atlantic Salmon (Salmo salar). We also conducted a genome-wide association analysis in Steelhead to assess whether additional regions were associated with this trait. We found the genetic basis of age at maturity to be heterogeneous across salmonid species. Significant associations between six6 and age at maturity were observed in two of the four species, Sockeye and Steelhead, with the association in Steelhead being particularly strong in both sexes (p = 4.46x10-9 after adjusting for genomic inflation). However, no significant associations were detected between age at maturity and the vgll3 genome region in any of the species, despite its strong association with the same trait in Atlantic Salmon. We discuss possible explanations for the heterogeneous nature of the genetic architecture of this key life-history trait, as well as the implications of our findings for conservation and management.

evolutionary biology↗

bioRxiv2019

Large single-locus effects for maturation timing are mediated via condition variation in Atlantic salmon

Maturation timing is a pivotal life-history trait balancing probabilities between mortality and reproduction. Environmental vs. genetic contributions to traits associated with maturation initiation, such as growth and body condition, remain uncertain because of difficulties in determining causality. In Atlantic salmon, maturation timing associates with a large-effect locus around vgll3, but how this locus affects maturation remains unknown. We combined controlled breeding with common-garden experimentation at two temperatures and show that vgll3 effects on maturation of males express primarily via body condition, which we demonstrate in the males non-maturing female relatives, thus avoiding reverse causality. Between homozygous vgll3 genotypes, maturation probability differed several folds and female condition differed 2% in both temperature environments. Vgll3 effects explained 25 and 16% of maturation probability heritability and 15 and 6% of female condition heritability, in the warm and cold environment, respectively. Non-significant vgll3 effects on female length were antagonistic to those on condition but of equal proportional size. When controlling for vgll3 effects, genetic correlations changed antagonistically between both maturation and condition vs. growth, suggesting vgll3 as a resource-allocation locus. The results support large vgll3 maturation effects being mediated via environmentally stable body condition effects, enabling rapid co-evolution between the life-history traits.

evolutionary biology↗

bioRxiv2019

Transcription profiles of age-at-maturity-associated genes suggest cell fate commitment regulation as a key factor in the Atlantic salmon maturation process

Despite recent taxonomic diversification in studies linking genotype with phenotype, follow-up studies aimed at understanding the molecular processes of such genotype-phenotype associations remain rare. The age at which an individual reaches sexual maturity is an important fitness trait in many wild species. However, the molecular mechanisms regulating maturation timing processes remain obscure. A recent genome-wide association study in Atlantic salmon (Salmo salar) identified large-effect age-at-maturity-associated chromosomal regions including genes vgll3, akap11 and six6, which have roles in adipogenesis, spermatogenesis and the hypothalamic-pituitary-gonadal (HPG) axis, respectively. Here, we determine expression patterns of these genes during salmon development and their potential molecular partners and pathways. Using Nanostring transcription profiling technology, we show development- and tissue-specific mRNA expression patterns for vgll3, akap11 and six6. Correlated expression levels of vgll3 and akap11, which have adjacent chromosomal location, suggests they may have shared regulation. Further, vgll3 correlating with arhgap6 and yap1, and akap11 with lats1 and yap1 suggests that Vgll3 and Akap11 take part in actin cytoskeleton regulation. Tissue-specific expression results indicate that vgll3 and akap11 paralogs have sex-dependent expression patterns in gonads. Moreover, six6 correlating with slc38a6 and rtn1, and Hippo signaling genes suggests that Six6 could have a broader role in the HPG neuroendrocrine and cell fate commitment regulation, respectively. We conclude that Vgll3, Akap11 and Six6 may influence Atlantic salmon maturation timing via affecting on adipogenesis and gametogenesis by regulating cell fate commitment and the HPG axis. These results may help to unravel general molecular mechanisms behind maturation.

genetics↗

bioRxiv2019

Regulatory divergence in vgll3 underlies variation in age at maturity in male Atlantic salmon

A major goal in biology is to understand how evolution shapes variation in individual life histories. Genome-wide association studies have been successful in uncovering genome regions linked with traits underlying life history variation in a range of species. However, lack of functional studies of the discovered genotype-phenotype associations severely restrains our understanding how alternative life history traits evolved and are mediated at the molecular level. Here, we report a cis-regulatory mechanism whereby expression of alternative isoforms of the transcription co-factor vestigial-like 3 (vgll3) associate with variation in a key life history trait, age at maturity, in Atlantic salmon (Salmo salar). Using a common-garden experiment, we first show that vgll3 genotype associates with puberty timing in one-year-old salmon males. By way of temporal sampling of vgll3 expression in ten tissues across the first year of salmon development, we identify a pubertal transition in vgll3 expression where maturation coincided with a 66% reduction in testicular vgll3 expression. The late maturation allele was not only associated with a tendency to delay puberty, but also with expression of a rare transcript isoform of vgll3 pre-puberty. By comparing absolute vgll3 mRNA copies in heterozygotes we show that the expression difference between the early and late maturity alleles is largely cis-regulatory. We propose a model whereby expression of a rare isoform from the late allele shifts the liability of its carriers towards delaying puberty. These results reveal how regulatory differences can be a central mechanism for the evolution of life history traits. Author summaryAlternative life history strategies are an important source of diversity within populations and promote the maintenance of adaptive capacity and population resilience. However, in many cases the molecular basis of different life history strategies remains elusive. Age at maturity is a key adaptive life history trait in Atlantic salmon and has a relatively simple genetic basis. Using salmon age at maturity as a model, we report a mechanism whereby different transcript isoforms of the key age at maturity gene, vestigial-like 3 (vgll3), associate with variation in the timing of male puberty. Our results show how gene regulatory differences in conjunction with variation in gene transcript structure can encode for complex alternative life histories.

evolutionary biology↗

bioRxiv2019

Life history genomic regions explain differences in Atlantic salmon marine diet specialization

O_LIAnimals employ various foraging strategies along their ontogeny to acquire energy, and with varying degree of efficiencies, to support growth, maturation and subsequent reproduction events. Individuals that can efficiently acquire energy early are more likely to mature at an earlier age, as a result of faster energy gain which can fuel maturation and reproduction. C_LIO_LIWe aimed to test the hypothesis that heritable resource acquisition variation that co-varies with efficiency along the ontogeny would influence maturation timing of individuals. C_LIO_LITo test this hypothesis, we utilized Atlantic salmon as a model which exhibit a simple, hence trackable, genetic control of maturation age. We then monitored the variation in diet acquisition (quantified as the stomach fullness and composition) of individuals with different ages, and linked it genomic regions (haploblocks) that were previously identified to be associated with age-at-maturity. C_LIO_LIConsistent with the hypothesis, we demonstrated that one of the life history genomic regions tested (six6) was indeed associated with age-dependent differences in stomach fullness. Prey composition was marginally linked to both genomic regions (six6 and vgll3). We further showed Atlantic salmon switched to the so-called "feast and famine" strategy along the ontogeny, where older age groups exhibited heavier stomach content, but that came at the expense of running on empty more often. C_LIO_LIThese results suggest genetic variation underlying resource utilization variation may explain the genetic basis of age structure in Atlantic salmon. Given that ontogenetic diet has a genetic component and the strong spatial diversity associated with these genomic regions, we predict populations with diverse maturation age will have diverse evolutionary responses to future changes in marine food-web structures. C_LI

ecology↗

bioRxiv2018

Genetic correlation between sea age at maturity and iteroparity in Atlantic salmon.

Genetic correlations in life history traits may result in unpredictable evolutionary trajectories if not accounted for in life-history models. Iteroparity (the reproductive strategy of reproducing more than once) in Atlantic salmon (Salmo salar) is a fitness trait with substantial variation within and among populations. In the Teno River in northern Europe, iteroparous individuals constitute an important component of many populations and have experienced a sharp increase in abundance in the last 20 years, partly overlapping with a general decrease in age structure. The physiological basis of iteroparity bears similarities to that of age at first maturity, another life history trait with substantial fitness effects in salmon. Sea age at maturity in Atlantic salmon is controlled by a major locus around the vgll3 gene, and we used this opportunity demonstrate that the two traits are genetically correlated around this genome region. The odds ratio of survival until second reproduction was up to 2.4 (1.8-3.5 90% CI) times higher for fish with the early-maturing vgll3 genotype (EE) compared to fish with the late-maturing genotype (LL). The association had a dominance architecture, although the dominant allele was reversed in the late-maturing group compared to younger groups that stayed only one year at sea before maturation. Post hoc analysis indicated that iteroparous fish with the EE genotype had accelerated growth prior to first reproduction compared to first-time spawners, across all age groups, while this effect was not detected in fish with the LL genotype. These results broaden the functional link around the vgll3 genome region and help us understand constraints in the evolution of life history variation in salmon. Our results further highlight the need to account for genetic correlations between fitness traits when predicting demographic changes in changing environments.

evolutionary biology↗