Iteroparity and its contribution to life-history variation in Atlantic salmon

Evolution of iteroparity is shaped by the trade-off between current and future reproduction.We studied variation in iteroparity among 205 050 individual Atlantic salmon caught in 179 rivers spanning 14◦ of latitude. The proportion of repeat spawners (iteroparous individuals) averaged 3.8% and ranged from 0% to 26% across rivers. Females were more often repeat spawners than males and had lower cost of reproduction in terms of lost body mass between spawning events. Proportion of repeat spawners for a given sea age at maturity, and the ratio of alternate to consecutive repeat spawners, increased with increasing population mean sea age at maturity. By combining smolt age, sea age at maturity, and age at additional spawning events, we identified 141 unique life-history types, and repeat spawners contributed 75% of that variation. Our results show that repeat spawners are important for life-history variation and suggest that the association between mean sea age and the frequency of repeat spawning is adaptive rather than a pleiotropic side effect arising from selection on sea age. age at maturity, life-history evolution, local adaptation, repeat spawning, trade-offpublishedVersio

Intersexual conflict over seed size is stronger in more outcrossed populations of a mixed-mating plant

In polyandrous species, fathers benefit from attracting greater maternal investment toward their offspring at the expense of the offspring of other males, while mothers should usually allocate resources equally among offspring. This conflict can lead to an evolutionary arms race between the sexes, manifested through antagonistic genes whose expression in offspring depends upon the parent of origin. The arms race may involve an increase in the strength of maternally versus paternally derived alleles engaged in a “tug of war” over maternal provisioning or repeated “recognition-avoidance” coevolution where growth-enhancing paternally derived alleles evolve to escape recognition by maternal genes targeted to suppress their effect. Here, we develop predictions to distinguish between these two mechanisms when considering crosses among populations that have reached different equilibria in this intersexual arms race. We test these predictions using crosses within and among populations of Dalechampia scandens (Euphorbiaceae) that presumably have experienced different intensities of intersexual conflict, as inferred from their historical differences in mating system. In crosses where the paternal population was more outcrossed than the maternal population, hybrid seeds were larger than those normally produced in the maternal population, whereas when the maternal population was more outcrossed, hybrid seeds were smaller than normal. These results confirm the importance of mating systems in determining the intensity of intersexual conflict over maternal investment and provide strong support for a tug-of-war mechanism operating in this conflict. They also yield clear predictions for the fitness consequences of gene flow among populations with different mating histories.acceptedVersion© 2018. This is the authors' accepted and refereed manuscript to the article. The final authenticated version is available online at: https://doi.org/10.1073/pnas.181097911

Inter-sexual parental conflict over seed provisioning in a mixed-mating vine

1. Sexual reproduction creates an arena for inter-sexual parental conflict. When multiple paternity occurs, paternal plants are selected to exploit maternal plants for resources invested in their seeds, at the expense of seeds sired by other pollen donors, while maternal plants are selected to allocate resources equally among seeds. This may result in a coevolutionary arms race between the sexes over maternal investment. This arms race may be mediated by uniparentally expressed genes with opposite effects on seed growth (kinship genomic imprinting) or by selfish paternal alleles evolving to escape recognition by maternal growth-suppressing genes (interlocus contest evolution). Crossing populations with different mating systems can reveal inter-sexual conflict, either because populations have reached different equilibria in the arms race and/or due to the fixation of different alleles involved in the conflict. 2. To test for the effect of mating system on hybrid seed size, I performed within and between-population crosses among four populations of the mixed-mating vine Dalechampia scandens (Euphorbiaceae), that differ in outcrossing rates. 3. When the paternal population was more outcrossed than the maternal population, hybrid seeds became larger than the seed size within the maternal population, and vice versa in the reciprocal cross. 4. The results support kinship genomic imprinting, that genes with antagonistic effects on seed growth have coevolved within populations, but that antagonistic forces acting on seed size are stronger in more outcrossed populations where inter-sexual parental conflict is expected to be more intense

Intersexual conflict over seed size is stronger in more outcrossed populations of a mixed-mating plant

Intersexual conflict over maternal resource allocation to offspring can lead to the evolution of imprinted genes with parentof- origin–specific expression. However, the precise mechanism involved in the evolution of such imprinted genes is less well understood, and few clear predictions have been presented.We resolve this issue, and, using different populations of a mixedmating plant, we demonstrate that more outcrossed paternal populations produce larger seeds when crossed with less outcrossed maternal populations, and vice versa. This provides clear support for a “tug-of-war” mechanism operating between maternally and paternally imprinted genes. Such a mechanism can have important consequences for local adaptation in offspring size in the presence of gene flow between populations with different mating systems.acceptedVersio

Is there more to within- plant variation in seed size than developmental noise?

Within-plant variation in seed size may merely reflect developmental instability, or it may be adaptive in facilitating diversifying bet-hedging, that is, production of phenotypically diverse offspring when future environments are unpredictable. To test the latter hypothesis, we analyzed patterns of variation in seed size in 11 populations of the perennial vine Dalechampia scandens grown in a common greenhouse environment. We tested whether population differences in the mean and variation of seed size covaried with environmental predictability at two different timescales. We also tested whether within-plant variation in seed size was correlated with independent measures of floral developmental instability and increased under stressful conditions. Populations differed genetically in the amount of seed-size variation occurring among plants, among infructescences within plants, and among seeds within infructescences. Within-individual variation was not detectably correlated with measures of developmental instability and did not increase under stress, but it increased weakly with short-term environmental unpredictability of precipitation at the source-population site. These results support the hypothesis that greater variation in seed size is adaptive when environmental predictability is low

Data and R scripts for: Variation in phenotypic plasticity across age-at-maturity genotypes in wild Atlantic salmon

<p>Data and R-scripts underlying the statistical analyses of the study. </p&gt

Intersexual conflict over seed size is stronger in more outcrossed populations of a mixed-mating plant

In polyandrous species, fathers benefit from attracting greater maternal investment toward their offspring at the expense of the offspring of other males, while mothers should usually allocate resources equally among offspring. This conflict can lead to an evolutionary arms race between the sexes, manifested through antagonistic genes whose expression in offspring depends upon the parent of origin. The arms race may involve an increase in the strength of maternally versus paternally derived alleles engaged in a “tug of war” over maternal provisioning or repeated “recognition-avoidance” coevolution where growth-enhancing paternally derived alleles evolve to escape recognition by maternal genes targeted to suppress their effect. Here, we develop predictions to distinguish between these two mechanisms when considering crosses among populations that have reached different equilibria in this intersexual arms race. We test these predictions using crosses within and among populations of Dalechampia scandens (Euphorbiaceae) that presumably have experienced different intensities of intersexual conflict, as inferred from their historical differences in mating system. In crosses where the paternal population was more outcrossed than the maternal population, hybrid seeds were larger than those normally produced in the maternal population, whereas when the maternal population was more outcrossed, hybrid seeds were smaller than normal. These results confirm the importance of mating systems in determining the intensity of intersexual conflict over maternal investment and provide strong support for a tug-of-war mechanism operating in this conflict. They also yield clear predictions for the fitness consequences of gene flow among populations with different mating histories

Forslag til definisjon av laksebestander

Karlsson, S., Diserud, O. H., Fiske, P., Forseth, T., Hagen, I. J., Hindar, K., Raunsgard, A., Skaala, Ø., Skoglund, H. & Sægrov, H. 2023. Forslag til definisjon av laksebestander. NINA Rapport 2266. Norsk institutt for naturforskning. Med utgangspunkt i Naturmangfoldloven og Lakse- og innlandsfiskeloven har forvaltningen som mål å ivareta artenes genetiske mangfold og opprettholde levedyktige bestander med naturgitt produktivitet. Den viktigste måleparameteren for hvorvidt dette forvaltningsmålet er nådd for laks er «Kvalitetsnorm for ville bestander av laks (Salmo salar)» som i hovedsak måler hvorvidt bestander har oppnådd gytebestandsmålet og har et høstbart overskudd, samt i hvilken grad bestandenes genetiske integritet er bevart. Forvaltningen skiller mellom vassdrag med laksebestander og vassdrag med forekomst av laks. Inndelingen i laksebestander og lakseforekomster har en direkte praktisk betydning, der de som blir klassifisert som bestand skal ha fiskereguleringer, skal vurderes i henhold til kvalitetsnormen, er gjenstand for utfisking av rømt oppdrettslaks, og kan bli prioritert for habitatforbedrende tiltak. Grensen for hva som er en laksebestand, og hva som er en forekomst, er i dag usikker og i liten grad definert utfra bevaringsbiologiske kriterier. I dette prosjektet har en ekspertgruppe på oppdrag fra Miljødirektoratet benyttet kunnskap og data for å foreslå en grense for å skille mellom en bestand og en forekomst og hvordan elvespesifikke egenskaper i form av vannføring, areal og produktivitet kan benyttes til klassifiseringen. Ekspertgruppen har lagt til grunn teoretiske forventninger omkring tap av genetisk variasjon og stokastiske populasjonsmodeller og foreslår en nedre grense for en laksebestand på 50 anadrome gytefisk. Data på forekomst og tetthet av laks i forhold til vannføring og areal har så blitt benyttet for å anslå hvilke vassdrag som potensielt kan ha en lakseproduksjon på et nivå tilsvarende grensen på antall gytefisk. Ekspertgruppen har utarbeidet et beslutningstre der det først skilles mellom vassdrag med en årsmiddelvannføring mindre eller større enn 0,6 m3/s, der vassdrag med en vannføring > 0,6 m3/s blir kategorisert som en potensiell laksebestand. Vassdrag med lavere vannføring kan kategoriseres som en potensiell laksebestand dersom det finnes en innsjø på lakseførende strekning og vannføringen er > 0,3 m3/s. Vassdrag som ikke møter disse kriteriene blir kategorisert som sjøørretvassdrag. For en videre kategorisering foreslår ekspertgruppen å knytte grensene til et gytebestandsmål. Kategorisering tar da utgangspunkt i at det er like mange hunner som hanner (25) og at gjennomsnittsstørrelsen på hunnfisken er 1,5 kg. Under disse forutsetningene blir definisjonsgrensen på 50 gytefisk for en laksebestand oversatt til et gytebestandsmål på 38 kg hunnlaks. Ut fra kombinasjoner av lakseførende areal og produktivitet (eggtetthetsklasse) har vi beregnet hvilke vassdrag som oppfyller dette gytebestandsmålet. En nedre grense på anadromt areal for en laksebestand blir da satt til 9 000 m2 dersom produktiviteten er svært høy (5-7 egg/m2), 13 000 m2 ved høy produktivitet (3-5 egg/m2), 27 000 m2 ved moderat produktivitet (1,5-3 egg/m2), og 54 000 m2 ved lav produktivitet (< 1,5 egg/m2). I henhold til oppdraget har ekspertgruppen forsøkt å oppnå en definisjon som er bevaringsbiologisk forankret, samtidig som den er pragmatisk og praktisk

Ecological regime shift in the Northeast Atlantic Ocean revealed from the unprecedented reduction in marine growth of Atlantic salmon

Ecological regime shifts are abrupt changes in the structure and function of ecosystems that persist over time, but evidence of contemporary regime shifts are rare. Historical scale data from 52,384 individual wild Atlantic salmon caught in 180 rivers from 1989 to 2017 reveal that growth of Atlantic salmon across the Northeast Atlantic Ocean abruptly decreased following the year 2004. At the same time, the proportion of early maturing Atlantic salmon decreased. These changes occurred after a marked decrease in the extent of Arctic water in the Norwegian Sea, a subsequent warming of spring water temperature before Atlantic salmon entering the sea, and an approximately 50% reduction of zooplankton across large geographic areas of the Northeast Atlantic Ocean. A sudden decrease in growth was also observed among Atlantic mackerel in the Norwegian Sea. Our results point toward an ecosystem-scale regime shift in the Northeast Atlantic Ocean

Ecological regime shift in the Northeast Atlantic Ocean revealed from the unprecedented reduction in marine growth of Atlantic salmon

Ecological regime shifts are abrupt changes in the structure and function of ecosystems that persist over time, but evidence of contemporary regime shifts are rare. Historical scale data from 52,384 individual wild Atlantic salmon caught in 180 rivers from 1989 to 2017 reveal that growth of Atlantic salmon across the Northeast Atlantic Ocean abruptly decreased following the year 2004. At the same time, the proportion of early maturing Atlantic salmon decreased. These changes occurred after a marked decrease in the extent of Arctic water in the Norwegian Sea, a subsequent warming of spring water temperature before Atlantic salmon entering the sea, and an approximately 50% reduction of zooplankton across large geographic areas of the Northeast Atlantic Ocean. A sudden decrease in growth was also observed among Atlantic mackerel in the Norwegian Sea. Our results point toward an ecosystem-scale regime shift in the Northeast Atlantic Ocean.publishedVersio