Lifetime fitness of short- and long-distance dispersing great reed warblers

Dispersal is of prime importance for many evolutionary processes and has been studied for decades. The reproductive consequences of dispersal have proven difficult to study, simply because it is difficult to keep track of dispersing individuals. In most previous studies evaluating the fitness effects of dispersal, immigrants at a study locality have been lumped into one category and compared to philopatric individuals. This is unfortunate, because there are reasons to believe that immigrants with long and short dispersal distances may differ substantially in reproductive success. In the present study, we used a combination of capture-recapturing and multilocus microsatellite genotyping to categorize great reed warblers at our Swedish study site as philopatric individuals or short- or long-distance dispersing immigrants. We then performed novel comparisons of lifetime reproductive success (LRS) and survival rates of these three dispersal categories. The birds belonged to cohorts 1987-1996, and data for their LRS were gathered between 1988 and 2003. The analyses showed that philopatric males attracted more females, produced more fledglings and recruits throughout their lives, and survived better than immigrants. Among the immigrant males, those categorized as long-distance dispersers had lowest LRS and survival probability. Models that included covariates of potential importance showed that the difference in LRS between dispersal categories was partly caused by corresponding variation in number of breeding years at our study site. These results indicate that short- and, in particular, long-distance dispersers were of poor phenotypic quality, but it may also be proposed that immigrants attracted few females because they were poorly adapted to the local social environment. In females, the number of local recruits corrected for the number of breeding years (as well as for number of fledglings) differed between dispersal categories in a pattern that suggests an intermediate optimal dispersal distance. Short-distance dispersers recruited more offspring per year (and per fledgling) than both philopatric individuals and long-distance dispersers. Data suggest that the low LRS of philopatric females was related to costs of inbreeding. The low LRS of long-distance dispersing females may have resulted from their offspring being especially prone to disperse outside the study area, but also other potential explanations exist, such as local maladaptation. Our study highlights the importance of separating immigrant birds on the basis of their genetic similarity to the local study population when analyzing variation in LRS and inferring realized gene flow.     

Sex-specific fitness correlates of dispersal in a house sparrow metapopulation

1.  Dispersal affects many important ecological and evolutionary processes. Still, little is known about the fitness of dispersing individuals.
2.  Here, we use data from a long-term study of a house sparrow Passer domesticus metapopulation to compare lifetime reproductive success (LRS) of resident and immigrant individuals, all with known origin.
3.  Lifetime production of recruits by immigrant males was much lower than for resident males, because of shorter life span and lower annual mating success. In contrast, lifetime production of recruits did not differ significantly between immigrant and resident females.
4.  Over their lifetime, dispersers contributed fewer recruits to the local population than residents. This shows that immigrant house sparrows have different, sex specific, demographic effects on the population dynamics than residents.     

A new approach to study dispersal: immigration of novel alleles reveals female-biased dispersal in great reed warblers

We use the assignment technique and a new approach, the 'novel allele technique', to detect sex-biased dispersal in great reed warblers Acrocephalus arundinaceus. The data set consisted of immigrants and philopatric birds in a semi-isolated population in Sweden scored at 21 microsatellite loci. Fourteen cohorts were represented of which the four earliest were used to define a reference population. Female immigrants had lower assignment probability than males (i.e. were less likely to have been sampled in the reference population), and carried the majority of 'novel alleles' (i.e. alleles observed in the population for the first time). The difference in number of novel alleles between sexes was caused by a strong over-representation of females among the few individuals that carried several novel alleles, and there was a tendency for a corresponding female bias among individuals with low assignment probabilities. Immigrant males had similar or lower reproductive success than females. These results lead us to conclude that important interregional gene flow in great reed warblers depends on relatively few dispersing females, and that the novel allele technique may be a useful complement to the assignment technique when evaluating dispersal patterns from temporally structured data.     

The sexy son hypothesis: data from the pied flycatcher Ficedula hypoleuca

The sexy son hypothesis has been proposed as a possible explanation for polygyny in territorial birds. Females mated with polygynous males are assumed to derive benefits in future generations through their ‘sexy’ sons, and hence they can afford to produce fewer offspring than simultaneously breeding monogamous females, the polygyny threshold thus being reduced. In the pied flycatcher, secondary females are not fully aided by males in feeding the nestlings, and they produce only 65% as many fledglings as do simultaneous monogamous and primary females. We have proposed male deception through polyterritoriality as the explanation for females ending up as secondary females, while some authors have advocated the sexy son hypothesis as an alternative. However, secondary females do not achieve benefits in future generations in this species. Repeatability of male mating status is far too low to grant any significant benefits through grandsons. In fact, offspring hatched in secondary female nests suffer from food shortage and therefore are of poor phenotypic quality with low fledging weight and short tarsus length. Therefore they are likely to enjoy lower reproductive success than offspring born in monogamous nests, as is illustrated by data on the relation between lifetime reproductive success and tarsus length. Altogether the applicability of the sexy son hypothesis is limited since it is based on the unrealistic assumption of relatively high heritability for a character with great influence on male fitness.     

The role of immigration and local adaptation on fine‐scale genotypic and phenotypic population divergence in a less mobile passerine

Dispersal and local patterns of adaptation play a major role on the ecological and evolutionary trajectory of natural populations. In this study, we employ a combination of genetic (25 microsatellite markers) and field‐based information (seven study years) to analyse the impact of immigration and local patterns of adaptation in two nearby (< 7 km) blue tit (Cyanistes caeruleus) populations. We used genetic assignment analyses to identify immigrant individuals and found that dispersal rate is female‐biased (72%). Data on lifetime reproductive success indicated that immigrant females produced fewer local recruits than their philopatric counterparts whereas immigrant males recruited more offspring than those that remained in their natal location. In spite of the considerably higher immigration rates of females, our results indicate that, in absolute terms, their demographic and genetic impact in the receiving populations is lower than that in immigrant males. Immigrants often brought novel alleles into the studied populations and a high proportion of them were transmitted to their recruits, indicating that the genetic impact of immigrants is not ephemeral. Although only a few kilometres apart, the two study populations were genetically differentiated and showed strong divergence in different phenotypic and life‐history traits. An almost absent inter‐population dispersal, together with the fact that both populations receive immigrants from different source populations, is probably the main cause of the observed pattern of genetic differentiation. However, phenotypic differentiation (P_ST) for all the studied traits greatly exceeded neutral genetic differentiation (F_ST), indicating that divergent natural selection is the prevailing factor determining the evolutionary trajectory of these populations. Our study highlights the importance of integrating individual‐ and population‐based approaches to obtain a comprehensive view about the role of dispersal and natural selection on structuring the genotypic and phenotypic characteristics of natural populations.     

扩散或不扩散：雄性太行山猕猴繁殖成功比较研究

典型的猕猴（Macaca multta）社群为多雄多雌型,雌性留群并形成母系单元,雄性多在亚成年或成年期离开出生群,而群内成年雄性多为外部迁入个体。雄性的迁出被认为可降低近亲繁殖或提升繁殖成功。然而,诸多野外数据显示,少数本群出生雄性个体会居留于出生群一年或数年。尽管驱动雄性离群的因素较复杂（如社会关系、近亲回避、繁殖成功）,但繁殖成功的差异可能是驱动雄性离群的主导因素。为探讨居留于出生群是否影响雄性的繁殖成功,于2010年3月至2014年1月,在太行山猕猴国家级自然保护区王屋山地区,以一群野生太行山猕猴为研究对象,采用非损伤取样法并结合分子生物学方法,分析了群内出生和迁入成年雄性个体的繁殖成功（以子代数量评估）。研究发现：(1)群内51只子代个体中有36只个体可以匹配到其遗传学父亲;(2)4个迁入雄性繁衍了34个子代,仅1只群内出生雄性ZM繁衍了2只子代,但群内出生的雄性BB未匹配到子代。本研究提示,迁入雄性较本群出生雄性的繁殖成功较高,即迁移有助于繁殖成功的提升。     

Early determinants of lifetime reproductive success differ between the sexes in red deer.

In polygynous, sexually dimorphic species, sexual selection should be stronger in males than in females. Although this prediction extends to the effects of early development on fitness, few studies have documented early determinants of lifetime reproductive success in a natural mammal population. In this paper, we describe factors affecting the reproductive success of male and female red deer (Cervus elaphus) on the island of Rum, Scotland. Birthweight was a significant determinant of total lifetime reproductive success in males, with heavier-born males being more successful than lighter ones. In contrast, birthweight did not affect female reproductive success. High population density and cold spring temperatures in the year of birth decreased several components of fitness in females, but did not affect the breeding success of males. The results confirm the prediction that selection on a sexually dimorphic trait should be greater in males than in females, and explain the differential maternal expenditure between sons and daughters observed in red deer. Differences between the sexes in the effects of environmental and phenotypic variation on fitness may generate differences in the amount of heritable genetic variation underlying traits such as birthweight.     

Physiological effects on demography: a long-term experimental study of testosterone's effects on fitness

Understanding physiological and behavioral mechanisms underlying the diversity of observed life-history strategies is challenging because of difficulties in obtaining long-term measures of fitness and in relating fitness to these mechanisms. We evaluated effects of experimentally elevated testosterone on male fitness in a population of dark-eyed juncos studied over nine breeding seasons using a demographic modeling approach. Elevated levels of testosterone decreased survival rates but increased success of producing extra-pair offspring. Higher overall fitness for testosterone-treated males was unexpected and led us to consider indirect effects of testosterone on offspring and females. Nest success was similar for testosterone-treated and control males, but testosterone-treated males produced smaller offspring, and smaller offspring had lower postfledging survival. Older, more experienced females preferred to mate with older males and realized higher reproductive success when they did so. Treatment of young males increased their ability to attract older females yet resulted in poor reproductive performance. The higher fitness of testosterone-treated males in the absence of a comparable natural phenotype suggests that the natural phenotype may be constrained. If this phenotype were to arise, the negative social effects on offspring and mates suggest that these effects might prevent high-testosterone phenotypes from spreading in the population.     

The new kid on the block: immigrant males win big whereas females pay fitness cost after dispersal

Dispersal is nearly universal; yet, which sex tends to disperse more and their success thereafter depends on the fitness consequences of dispersal. We asked if lifetime fitness differed between residents and immigrants (successful between‐population dispersers) and their offspring using 29 years of monitoring from North American red squirrels (Tamiasciurus hudsonicus) in Canada. Compared to residents, immigrant females had 23% lower lifetime breeding success (LBS), while immigrant males had 29% higher LBS. Male immigration and female residency were favoured. Offspring born to immigrants had 15–43% lower LBS than offspring born to residents. We conclude that immigration benefitted males, but not females, which appeared to be making the best of a bad lot. Our results are in line with male‐biased dispersal being driven by local mate competition and local resource enhancement, while the intergenerational cost to immigration is a new complication in explaining the drivers of sex‐biased dispersal.     

The effects of dominance rank and group size on female lifetime reproductive success in wild long-tailed macaques,Macaca fascicularis

Demographic changes were recorded throughout a 12-year period for three social groups ofMacaca fascicularis in a natural population at Ketambe (Sumatra, Indonesia). We examined the prediction that females' lifetime reproductive success depended on dominance rank and group size. Average birth rate was 0.53 (184 infants born during 349 female years). For mature females (aged 8–20 yr) birth rate reflected physical condition, being higher in years with high food availability and lower in the year following the production of a surviving infant. High-ranking females were significantly more likely than low-ranking ones to give birth again when they did have a surviving offspring born the year before (0.50 vs 0.26), especially in years with relatively low food availability (0.37 vs 0.10). Controlled comparisons of groups at different sizes indicate a decline in birth rate with rroup size only once a group has exceeded a certain size. The dominance effect on birth rate tended to be strongest in large groups. Survival of infants was rank-dependent, but the survival of juveniles was not. There was a trend for offspring survival to be lower in large groups than in mid-sized or small groups. However, rank and group size interacted, in that rank effects on offspring survival were strongest in large groups. High-ranking females were less likely to die themselves during their top-reproductive years, and thus on average had longer reproductive careers. We estimated female lifetime reproductive success based on calculated age-specific birth rates and survival rates. The effects of rank and group size (contest and scramble) on birth rate, offspring survival, age of first reproduction for daughters, and length of reproductive career, while not each consistently statistically significant, added up to substantial effects on estimated lifetime reproductive success. The group size effects explain why large groups tend to split permanently. Since females are philopatric in this species, and daughters achieve dominance rank positions similar to their mother, a close correlation is suggested between the lifetime reproductive success of mothers and daughters. For sons, too, maternal dominance affected their reproductive success: high-born males were more likely to become top-dominant (in another group). These data support the idea that natural selection has favored the evolution of a nepotistic rank system in this species, even if the annual benefits of dominance are small.     

Heterosis and outbreeding depression in descendants of natural immigrants to an inbred population of song sparrows (Melospiza melodia)

We studied heterosis and outbreeding depression among immigrants and their descendants in a population of song sparrows on Mandarte Island, Canada. Using data spanning 19 generations, we compared survival, seasonal reproductive success, and lifetime reproductive success of immigrants, natives (birds with resident-hatched parents and grandparents), and their offspring (F1s, birds with an immigrant and a native parent, and F2s, birds with an immigrant grandparent and resident-hatched grandparent in each of their maternal and paternal lines). Lifetime reproductive success of immigrants was no worse than that of natives, but other measures of performance differed in several ways. Immigrant females laid later and showed a tendency to lay fewer clutches, but had relatively high success raising offspring per egg produced. The few immigrant males survived well but were less likely to breed than native males of the same age that were alive in the same year. Female F1s laid earlier than expected based on the average for immigrant and native females, and adult male F1s were more likely to breed than expected based on the average for immigrant and native males. The performance differences between immigrant and native females and between F1s and the average of immigrants and natives are consistent with the hypothesis that immigrants were disadvantaged by a lack of site experience and that immigrant offspring benefited from heterosis. However, we could not exclude the possibility that immigrants had a different strategy for optimizing reproductive success or that they experienced ecological compensation for life-history parameters. For example, the offspring of immigrants may have survived well because immigrants laid later and produced fewer clutches, thereby raising offspring during a period of milder climatic conditions. Although sample sizes were small, we found large performance differences between F1s and F2s, which suggested that either heterosis was associated with epistasis in F1s, that F2s experienced outbreeding depression, or that both phenomena occurred. These findings indicate that the performance of dispersers may be affected more by fine-scale genetic differentiation than previously assumed in this and comparable systems.     

Lifetime fitness and age‐related female ornament signalling: evidence for survival and fecundity selection in the pied flycatcher

Ornaments displayed by females have often been denied evolutionary interest due to their frequently reduced expression relative to males, habitually attributed to a genetic correlation between the sexes. We estimated annual and lifetime reproductive success of female pied flycatchers (Ficedula hypoleuca) and applied capture–mark–recapture models to analyse annual survival rates in relation to the patterns of expression (absence/presence) of an ornament displayed by all males and a fraction of females. Overall, the likelihood of expressing the ornament increased nonlinearly with female age and was due to within‐individual variation, not to the selective appearance or disappearance of ornament‐related expression of phenotypes in the population. Accordingly, expressing the forehead patch in a given year did not influence survival probability. However, those females expressing the ornament at early ages (1–2 years old) enjoyed survival advantages throughout lifetime. Although ornamented females had higher lifetime fecundity and fledging success, their yearly reproductive performance, in terms of fledging productivity, decreased as they aged so that, late in life, ornamented females reared fewer offspring than nonexpressing females of the same age. In addition, both strategies (expressing vs. not expressing the trait) returned similar fitness payoffs in terms of recruited offspring. Our results support the hypothesis that fecundity and survival selection are involved in the displaying of this ‘male’ ornament by females.     

Lifetime reproductive success of female mountain gorillas

Studies of lifetime reproductive success (LRS) are important for understanding population dynamics and life history strategies, yet relatively little information is available for long-lived species. This study provides a preliminary assessment of LRS among female mountain gorillas in the Virunga volcanoes region. Adult females produced an average of 3.6 ± 2.1 surviving offspring during their lifetime, which indicates a growing population that contrasts with most other great apes. The standardized variance in LRS (variance/mean(2) = 0.34) was lower than many other mammals and birds. When we excluded the most apparent source of environmental variability (poaching), the average LRS increased to 4.3 ± 1.8 and the standardized variance dropped in half. Adult lifespan was a greater source of variance in LRS than fertility or offspring survival. Females with higher LRS had significantly longer adult lifespans and higher dominance ranks. Results for LRS were similar to another standard fitness measurement, the individually estimated finite rate of increase (λ(ind) ), but λ(ind) showed diminishing benefits for greater longevity.     

Breeding dispersal strategies following reproductive failure explain low apparent survival of immigrant Temminck's stints

In some animal populations, immigrants have lower survival than philopatric individuals. Costs of dispersal or low phenotypic quality of dispersers may explain the pattern. However, apparent adult survival estimates, which describe real survival combined with site fidelity cannot be separated from permanent emigration. Thus, heterogeneity in breeding dispersal propensities of immigrants and philopatrics can bias fitness correlates of dispersal. Differences in breeding dispersal propensities may be caused by different strategies in response to environmental cues inducing dispersal, such as reproductive success. In such cases, the reported differences between immigrants and philopatric individuals may not reflect true variation in survival. We studied whether dispersal status specific apparent adult survival is associated with reproductive success in a Temminck's stint Calidris temminckii population. We analysed two long term capture–recapture datasets characterised by low and high nest predation levels. Philopatric individuals had higher apparent adult survival than immigrants in both datasets and the difference was highlighted during the high nest predation period. By contrasting return rates between successful and unsuccessful breeders as a proxy for dispersal, we found that unsuccessful immigrants breeding for the first time dispersed more likely than successful immigrants, but such a pattern was not found among philopatric individuals. Our results support the hypothesis that immigrant and philopatric individuals have different breeding dispersal strategies following reproductive failure and that their apparent adult survival differences are at least partly explained by different breeding dispersal propensities. Our results also suggest that the recent decline of the study population reflects a multiple response to increased nest predation through decreased local recruitment and increased emigration.     

Differences in Patterns of Reproductive Allocation between the Sexes in Nicrophorus orbicollis

Organisms are selected to maximize lifetime reproductive success by balancing the costs of current reproduction with costs to future survival and fecundity. Males and females typically face different reproductive costs, which makes comparisons of their reproductive strategies difficult. Burying beetles provide a unique system that allows us to compare the costs of reproduction between the sexes because males and females are capable of raising offspring together or alone and carcass preparation and offspring care represent the majority of reproductive costs for both sexes. Because both sexes perform the same functions of carcass preparation and offspring care, we predict that they would experience similar costs and have similar life history patterns. In this study we assess the cost of reproduction in male Nicrophorus orbicollis and compare to patterns observed in females. We compare the reproductive strategies of single males and females that provided pre- and post-hatching parental care. There is a cost to reproduction for both males and females, but the sexes respond to these costs differently. Females match brood size with carcass size, and thus maximize the lifetime number of offspring on a given size carcass. Males cull proportionately more offspring on all carcass sizes, and thus have a lower lifetime number of offspring compared to females. Females exhibit an adaptive reproductive strategy based on resource availability, but male reproductive strategies are not adaptive in relation to resource availability.     

Relative fitness of alternative male reproductive tactics in a mammal varies between years

1. In many species, males can use different behavioural tactics to achieve fertilization, so-called alternative reproductive tactics (ARTs). Few field studies have measured fitness consequences of ARTs under varying environmental conditions. 2. Here, we describe fitness consequences of three phenotypically plastic ARTs in the African striped mouse (Rhabdomys pumilio) and show that relative fitness of ARTs differs between years. Each year represents a different generation. 3. For the generation living under high population density, tactics differed in relative fitness in accordance with the theory of conditional strategies, with highly successful territorial breeding males having 10 times higher success than solitary roaming males and 102 times higher success than adult natally philopatric males. 4. For the generation living under intermediate population density, the territorial breeding and roaming tactics yielded similar fitness, which would be in agreement with the theory of mixed strategies. No philopatric males occurred. 5. For the generation living under low population density, roaming was the only tactic used and some roamers had very high fitness. 6. The main prediction of status-dependent selection for conditional strategies is a correlation between fitness and status, often measured as body mass, but we did not find this correlation within tactics when more than one tactic was expressed in the population. 7. Female distribution seems to have an effect on which reproductive tactics male chose: female defence polygyny when females are clumped (interference competition), but a searching tactic when females are dispersed (scramble competition). In contrast to predictions arising from theory on scramble competition, male body mass was important in determining fitness only in the year when females were dispersed, but not in other years. 8. Our results indicate that the differentiation between conditional and mixed strategies is not an absolute one. In many other species, environmental conditions might fluctuate temporally and spatially so that the normally suboptimal tactic yields similar fitness to the (usually) dominant tactic or that only a single tactic prevails. 9. We suggest the term single strategy, independent of current fitness consequences, for systems where tactics are not genetically determined, in contrast to genetically determined alternative strategies.     

Female competition in chimpanzees

Female chimpanzees exhibit exceptionally slow rates of reproduction and raise their offspring without direct paternal care. Therefore, their reproductive success depends critically on long-term access to high-quality food resources over a long lifespan. Chimpanzee communities contain multiple adult males, multiple adult females and their offspring. Because males are philopatric and jointly defend the community range while most females transfer to new communities before breeding, adult females are typically surrounded by unrelated competitors. Communities are fission–fusion societies in which individuals spend time alone or in fluid subgroups, whose size depends mostly on the abundance and distribution of food. To varying extents in different populations, females avoid direct competition by foraging alone or in small groups in distinct, but overlapping core areas within the community range to which they show high fidelity. Although rates of aggression are low, females compete for space and access to food. High rank correlates with high reproductive success, and high-ranking females win direct contests for food and gain preferential access to resource-rich sites. Females are aggressive to immigrant females and even kill the newborn infants of community members. The intensity of such aggression correlates with population density. These patterns are compared to those in other species, including humans.     

Immigration and gene flow in a northern willow tit (Parus montanus) population

To study quantitatively the relationship between immigration rate and gene flow we used 9-year data from a willow tit Parus montanus population in a continuous forest habitat. We compared components of lifetime reproductive success, and parental survival rate between immigrant and resident (‘status’) birds by taking individual age into consideration also. Of the fitness components, survival was independent of status and sex, averaging 0.60 annually. Of the male and female breeders, on average 63.1% and 75.6%, respectively, originated from unknown natal areas, implying extensive immigration. Pair formation was nonassortative with respect to the origin of partners. The effect of status on reproductive success was significant only for females: immigrants produced larger clutches and hatched more young in all age classes studied. However, the difference between the groups diminished until fledging and the offspring produced by the immigrant females showed lower local survival rate (4.6% of the young) than did those by the residents (5.9%). Therefore, the contribution of immigrant females to the local gene pool was lower than expected on the basis of immigration rate. However, we propose that the result implies differential propensities to long-distance dispersal rather than overall survival prospects, since we detected no quality differences suggesting reduced survival chances among descendants of immigrant females. Therefore, gene flow into the population was slightly lower than immigration rate. It is possible that immigrant females are more prone to invest in progeny that effectively disperse further to search for new vacancies. The conditions prevailing during nestling growth may be crucial in determining whether an individual will later become a resident or leave the natal area, but the genetic component of this trait should also be considered. We suggest that widespread propagules is a better strategy than philopatry for a short-lived species to minimize the risk of losing all descendants in temporally and spatially varying conditions.     

Age-specific mating strategies and reproductive senescence

While males gain obvious direct advantages from multiple mating, the reproductive capacity of females is more constrained. The reason why polyandry evolved in females is therefore open to many conjectures. One hypothesis postulates that females gain indirect benefits by increasing the probability of siring young from high quality males. To explore this hypothesis, we used the natural variation of the reproductive value that males and females undergo through age. The age-related variation of phenotypic performance might then induce variations in mating strategies in males and females. Using the common lizard (Lacerta vivipara) as our model system, we showed that reproductive immaturity and senescence created variability in both male and female reproductive success (including survival of offspring). Consistent with theory, males at their best-performing phenotype adopted a polygynous strategy. These males were of an intermediate age and they produced offspring of higher viability than younger and older males. In contrast, females at their best performing phenotype, also of an intermediate age, were less polyandrous than other less-performing females. Middle-aged females tended to mate with males of an intermediate age and produced litters with higher viability independently from their reproductive strategy. Males of an intermediate age enhanced their fitness by additional matings with young or old females. Young and old females increased their fitness by being more polyandrous. Polyandry therefore appears as means to seek for good males. A positive correlation between males and their partners' fitness disagree with the idea that polyandry is the result of a sexual conflict in this species.     

Time spent in distinct life history stages has sex‐specific effects on reproductive fitness in wild Atlantic salmon

In species with complex life cycles, life history theory predicts that fitness is affected by conditions encountered in previous life history stages. Here, we use a 4‐year pedigree to investigate if time spent in two distinct life history stages has sex‐specific reproductive fitness consequences in anadromous Atlantic salmon (Salmo salar). We determined the amount of years spent in fresh water as juveniles (freshwater age, FW, measured in years), and years spent in the marine environment as adults (sea age, SW, measured in sea winters) on 264 sexually mature adults collected on a river spawning ground. We then estimated reproductive fitness as the number of offspring (reproductive success) and the number of mates (mating success) using genetic parentage analysis (>5,000 offspring). Sea age is significantly and positively correlated with reproductive and mating success of both sexes whereby older and larger individuals gained the highest reproductive fitness benefits (females: 62.2% increase in offspring/SW and 34.8% increase in mate number/SW; males: 201.9% offspring/SW and 60.3% mates/SW). Younger freshwater age was significantly related to older sea age and thus increased reproductive fitness, but only among females (females: ?33.9% offspring/FW and ?32.4% mates/FW). This result implies that females can obtain higher reproductive fitness by transitioning to the marine environment earlier. In contrast, male mating and reproductive success was unaffected by freshwater age and more males returned at a younger age than females despite the reproductive fitness advantage of later sea age maturation. Our results show that the timing of transitions between juvenile and adult phases has a sex‐specific consequence on female reproductive fitness, demonstrating a life history trade‐off between maturation and reproduction in wild Atlantic salmon.