Current Reproduction Research Articles

Carry-over effects on the annual cycle of a migratory seabird: an experimental study.

Summary Long‐lived migratory animals must balance the cost of current reproduction with their own condition ahead of a challenging migration and future reproduction. In these species, carry‐over effects, which occur when events in one season affect the outcome of the subsequent season, may be particularly exacerbated. However, how carry‐over effects influence future breeding outcomes and whether (and how) they also affect behaviour during migration and wintering is unclear.Here we investigate carry‐over effects induced by a controlled, bidirectional manipulation of the duration of reproductive effort on the migratory, wintering and subsequent breeding behaviour of a long‐lived migratory seabird, the Manx shearwater Puffinus puffinus. By cross‐fostering chicks of different age between nests, we successfully prolonged or shortened by ∼25% the chick‐rearing period of 42 breeding pairs. We tracked the adults with geolocators over the subsequent year and combined migration route data with at‐sea activity budgets obtained from high‐resolution saltwater‐immersion data. Migratory behaviour was also recorded during non‐experimental years (the year before and/or two years after manipulation) for a subset of birds, allowing comparison between experimental and non‐experimental years within treatment groups.All birds cared for chicks until normal fledging age, resulting in birds with a longer breeding period delaying their departure on migration; however, birds that finished breeding earlier did not start migrating earlier. Increased reproductive effort resulted in less time spent at the wintering grounds, a reduction in time spent resting daily and a delayed start of breeding with lighter eggs and chicks and lower breeding success the following breeding season. Conversely, reduced reproductive effort resulted in more time resting and less time foraging during the winter, but a similar breeding phenology and success compared with control birds the following year, suggesting that ‘positive’ carry‐over effects may also occur but perhaps have a less long‐lasting impact than those incurred from increased reproductive effort.Our results shed light on how carry‐over effects can develop and modify an adult animal's behaviour year‐round and reveal how a complex interaction between current and future reproductive fitness, individual condition and external constraints can influence life‐history decisions.

Influence of predator cues on terminal investment in courtship by maleSchizocosa ocreata(Hentz, 1844) wolf spiders (Araneae: Lycosidae)

Abstract Sexual signals play a critical role in mate attraction, but fitness benefits of signal production depend on a number of external and internal influences. Sexual signaling can be energetically expensive, and has potential to attract unwanted attention from predators. Male brushlegged wolf spiders, Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae), actively signal to females in the leaf litter habitat during their spring breeding season, but face a tradeoff between current and future reproduction as the season progresses. The terminal investment hypothesis predicts that with fewer available females, increasing risk of predation, and stronger influence of senescence as the season progresses, males should take greater risks to secure mating. We explored this idea by exposing males of increasing ages to female cues alone or female cues combined with predator cues. We found little or no direct evidence to support the terminal investment hypothesis in this species, in that males across all ages esse...

Back to perennials: Does selection enhance tradeoffs between yield and longevity?

Perennial plants allocate more resources belowground and have longer-lived leaves than their annual counterparts, which are the basis for the promotion of perennial crops towards a more sustainable agriculture. On the downside, perennial plants selected for high seed-yield might show tradeoffs between current reproduction and long-term reproduction or survival, raising the questions of whether this high yield can be sustained over time and whether such tradeoffs can be overcome through selection. We compared growth, reproduction and the storage of reserves, over 3 years in wild and high-yielding accessions of Physaria mendocina. We found evidence of a tradeoff between current and future reproduction, responsible for a decrease in yield with age, in selected accessions. Selected accession had 76% more accumulated seed-yield in relation to wild accessions, but they also concentrated seed-yield and had an enhanced harvest index in the first year. Wild accessions maintained seed production over time. Resources allocated to reproduction were limited for both root allocation and carbohydrate accumulation after the second year. Wild and selected accessions consumed half of their storage carbon during reproduction, but replenishment of storage organs was 60% lower in selected accession compared to wild ones. This response could be related to a lower recovery of the root system after senescence. Empirical information about the pattern of use of reserves and their relationships with the ontogenetic changes in leaf functioning and root architecture is crucial when defining new criteria of selection of perennial species, since they will influence longevity and yield stability.

Maternal effects on offspring size in a natural population of the viviparous tsetse fly

1. Theory predicts that mothers should adaptively adjust reproductive investment depending on current reserves and future reproductive opportunities. Females in better intrinsic state, or with more resources, should invest more in current reproduction than those with fewer resources. Across the lifespan, investment may increase as future reproductive opportunities decline, yet may also decline with reductions in intrinsic state.2. Across many species, larger mothers produce larger offspring, but there is no theoretical consensus on why this is so. This pattern may be driven by variation in maternal state such as nutrition, yet few studies measure both size and nutritional state or attempt to tease apart confounding effects of size and age.3. Viviparous tsetse flies (Glossina species) offer an excellent system to explore patterns of reproductive investment: females produce large, single offspring sequentially over the course of their relatively long life. Thus, per‐brood reproductive effort can be quantified by offspring size.4. While most tsetse reproduction research has been conducted on laboratory colonies, maternal investment was investigated in this study using a unique field method where mothers were collected as they deposited larvae, allowing simultaneous mother‐offspring measurements under natural conditions.5. It was found that larger mothers and those with a higher fat content produced larger offspring, and there was a trend for older mothers to produce slightly larger offspring.6. The present results highlight the importance of measuring maternal nutritional state, rather than size alone, when considering maternal investment in offspring. Implications for understanding vector population dynamics are also discussed.

Great tits trade off future competitive advantage for current reproduction

Quantifying the fitness costs of reproduction is essential to understand the evolution of reproductive behavior. Recent work shows that increased reproductive investment reduced parental survival in more competitive environments. Here we experimentally test the hypothesis that reproductive investment has a negative effect on the ability of parents to compete for resources in later life. In a nest-box population of Great tits (Parus major), we manipulated family size by reducing or enlarging broods with 2 or 3 nestlings, relative to a control group, in 2 years (N = 237 broods). Parental feeding effort was positively related to experimental family size but leveled off for the enlarged broods. In the next breeding season we manipulated the nest box quality in early spring by reducing the depth of 80% of the nest boxes (deeper boxes are safer and preferred). We analyzed parents' probability of obtaining a deep breeding box in relation to their previous year's family size manipulation. We found for both years that increased reproductive investment negatively affected the probability of parents to claim a high-quality nest box in the subsequent breeding season. We thus confirm that family size has a negative effect on the future competitive ability of parents. Such carry-over effects are important because they show that selection on individual optimal clutch size will depend on 1) resource abundance and the level of competition in the next breeding season and 2) the reproductive investment of the competitors in the current breeding season because it affects their future competitive ability as well.

When relative allocation depends on total resource acquisition: implication for the analysis of trade-offs.

A central tenet of evolutionary biology states that life-history traits are linked via trade-offs, as classically exemplified by the van Noordwijk and de Jong model. This model, however, assumes that the relative resource allocation to a biological function varies independently of the total resource acquisition. Based on current empirical evidence, we first explored the dependency between the total resource acquisition and the relative resource allocation to reproduction and showed that such dependency is the rule rather than the exception. We then derived the expression of the covariance between traits when the assumption of independence is relaxed and used simulations to quantify the importance of such dependency on the detection of trade-offs between current reproduction and future survival. We found that the dependency between the total energy acquisition and the relative allocation to reproduction can influence the probability to detect trade-offs between survival and reproduction. As a general rule, a negative dependency between the total energy acquisition and the relative allocation to reproduction should lead to a higher probability of detecting a trade-off in species with a fast pace of life, whereas a positive dependency should lead to a higher probability of detecting a trade-off in species with a slow pace of life. In addition to confirming the importance of resource variation to reveal trade-offs, our finding demonstrates that the covariance between resource allocation and resource acquisition is generally not null and also plays a fundamental role in the detection of trade-offs.

Reproductive investment is connected to innate immunity in a long-lived animal.

Life-history theory predicts that organisms optimize their resource allocation strategy to maximize lifetime reproductive success. Individuals can flexibly reallocate resources depending on their life-history stage, and environmental and physiological factors, which lead to variable life-history strategies even within species. Physiological trade-offs between immunity and reproduction are particularly relevant for long-lived species that need to balance current reproduction against future survival and reproduction, but their underlying mechanisms are poorly understood. A major unresolved issue is whether the first-line innate immune function is suppressed by reproductive investment. In this paper, we tested if reproductive investment is associated with the suppression of innate immunity, and how this potential trade-off is resolved depending on physiological state and residual reproductive value. We used long-lived capital-breeding female eiders (Somateria mollissima) as a model. We showed that the innate immune response, measured by plasma bacteria-killing capacity (BKC), was negatively associated with increasing reproductive investment, i.e., with increasing clutch size and advancing incubation stage. Females in a better physiological state, as indexed by low heterophil-to-lymphocyte (H/L) ratios, showed higher BKC during early incubation, but this capacity decreased as incubation progressed, whereas females in poorer state showed low BKC capacity throughout incubation. Although plasma BKC generally declined with increasing H/L ratios, this decrease was most pronounced in young females. Our results demonstrate that reproductive investment can suppress constitutive first-line immune defence in a long-lived bird, but the degree of immunosuppression depends on physiological state and age.

Impact of spatial variation of a crucial prey, the molecricket, on hoopoe territory occupancy and reproduction

Direct benefits accrued from securing a territory of sufficient quality are important determinants of individual fitness and population persistence. Food supply is one of the main factors of animal territory quality, with spatial and temporal variation in prey availability largely dictating reproductive output and thus population dynamics. In a Swiss hoopoe population, molecrickets Gryllotalpa gryllotalpa, the most profitable prey locally, can constitute most of the food biomass delivered to chicks by parents. We first investigated the impact of molecricket prey on hoopoes' fitness‐related traits by quantifying the spatial variation in the food allocation pattern of both male and female parents to chicks across the whole population range; and second, analysed the impact of this prey on current reproduction and, using a 11 yr dataset, on the temporal occupancy rate of each territory. We found considerable but spatially repeatable variation, over the years, of molecricket biomass in the diet provisioned to chicks. This spatial heterogeneity in chicks' diet composition was mirrored both in the history of territory occupancy (2002–2012) and in current reproductive success (2012). Territories with a greater biomass of molecrickets in chicks' diet produced more fledglings in better body condition. Yet, these effects on current reproduction were exclusively demonstrated for male parents, corroborating that paternal provisioning patterns play a predominant role in hoopoe reproductive success. This study demonstrates how a single, very profitable prey species might affect spatial variation in territory settlement and individual reproductive success in a regionally endangered bird species, with potential consequences for its population dynamics and persistence.

Male-biased hermaphrodites in a gynodioecious shrub, Daphne jezoensis.

Gynodioecy, a state where female and hermaphrodite plants coexist in populations, has been widely proposed an intermediate stage in the evolutionary pathway from hermaphroditism to dioecy. In the gynodioecy-dioecy pathway, hermaphrodites may gain most of their fitness through male function once females invade populations. To test this prediction, comprehensive studies on sex ratio variation across populations and reproductive characteristics of hermaphrodite and female phenotypes are necessary. This study examined the variation in sex ratio, sex expression, flower and fruit production and sexual dimorphism of morphological traits in a gynodioecious shrub, Daphne jezoensis, over multiple populations and years. Population sex ratio (hermaphrodite:female) was close to 1:1 or slightly hermaphrodite-biased. Sex type of individual plants was largely fixed, but 15% of plants changed their sex during a 6-year census. Hermaphrodite plants produced larger flowers and invested 2.5 times more resources in flower production than female plants, but they exhibited remarkably low fruit set (proportion of flowers setting fruits). Female plants produced six times more fruits than hermaphrodite plants. Low fruiting ability of hermaphrodite plants was retained even when hand-pollination was performed. Fruit production of female plants was restricted by pollen limitation under natural conditions, irrespective of high potential fecundity, and this minimised the difference in resources allocated to reproduction between the sexes. Negative effects of previous flower and fruit production on current reproduction were not apparent in both sexes. This study suggests that gynodioecy in this species is functionally close to a dioecious mating system: smaller flower production with larger fruiting ability in female plants, and larger flower production with little fruiting ability in hermaphrodite plants.

Decades of field data reveal that turtles senesce in the wild

Lifespan and aging rates vary considerably across taxa; thus, understanding the factors that lead to this variation is a primary goal in biology and has ramifications for understanding constraints and flexibility in human aging. Theory predicts that senescence-declining reproduction and increasing mortality with advancing age-evolves when selection against harmful mutations is weaker at old ages relative to young ages or when selection favors pleiotropic alleles with beneficial effects early in life despite late-life costs. However, in many long-lived ectotherms, selection is expected to remain strong at old ages because reproductive output typically increases with age, which may lead to the evolution of slow or even negligible senescence. We show that, contrary to current thinking, both reproduction and survival decline with adult age in the painted turtle, Chrysemys picta, based on data spanning >20 y from a wild population. Older females, despite relatively high reproductive output, produced eggs with reduced hatching success. Additionally, age-specific mark-recapture analyses revealed increasing mortality with advancing adult age. These findings of reproductive and mortality senescence challenge the contention that chelonians do not age and more generally provide evidence of reduced fitness at old ages in nonmammalian species that exhibit long chronological lifespans.

Sex differences in the behavior of wild Alouatta caraya infants.

Several primates show sex-based differences in activity patterns and social interactions during infancy. These differences have been associated with adult social and reproductive functions of males and females and are related to male-male competition. Our goal was to describe behavioral patterns of wild Alouatta caraya male and female infants, a species with sexual dimorphism in body size and behavioral strategies during adulthood. We also examined the relationship between life history variables, infant sex and age, activity patterns, and social interactions in order to determine whether males and females follow different trajectories during early growth. Over a 27-month study, we observed 21 male infants and 14 female infants across two similar sites in northern Argentina. Data were analyzed using generalized linear mixed model (GLMM) tests. We found no differences in suckling time or weaning age between males and females (9.7 vs. 9.4months), but male infants spent more time feeding on solid food and resting than female infants. Males also invested more time in contact with their mothers than did female infants, and mothers rejected and broke contact with males more frequently than with females. Other behavioral categories did not differ between the sexes. Our results suggest that higher nutritional demands of males compared with females may affect some behaviors. However, mothers of sons did not experience immediate trade-offs between current and future reproduction. Other behaviors, similarly expressed by the two sexes, suggest a similar developmental trajectory between male and female A. caraya infants, meaning that most differences emerge following the infant period.

The life-history basis of behavioural innovations.

The evolutionary origin of innovativeness remains puzzling because innovating means responding to novel or unusual problems and hence is unlikely to be selected by itself. A plausible alternative is considering innovativeness as a co-opted product of traits that have evolved for other functions yet together predispose individuals to solve problems by adopting novel behaviours. However, this raises the question of why these adaptations should evolve together in an animal. Here, we develop the argument that the adaptations enabling animals to innovate evolve together because they are jointly part of a life-history strategy for coping with environmental changes. In support of this claim, we present comparative evidence showing that in birds, (i) innovative propensity is linked to life histories that prioritize future over current reproduction, (ii) the link is in part explained by differences in brain size, and (iii) innovative propensity and life-history traits may evolve together in generalist species that frequently expose themselves to novel or unusual conditions. Combined with previous evidence, these findings suggest that innovativeness is not a specialized adaptation but more likely part of a broader general adaptive system to cope with changes in the environment.

Ruido visual: La saturación de imágenes en la contemporaneidad

La actualidad está marcada por la superproducción y consumo de imágenes que constituyen uno de los pilares de lo que se ha denominado cultura visual. La velocidad con la que actualmente se re-producen las imágenes, satura nuestra capacidad de discernir e interpretar, generando situaciones que desbordan nuestro poder de asimilación, y anula los tiempos para el análisis que precisa una mirada crítica. Ante esta espectacular densificación de la iconosfera, planteamos el concepto deruido visualcomo metáfora de esta circunstancia de sobreexposición al entramado audiovisual a la que nos vemos sometidos continuamente. La aceleración de los acontecimientos y las transformaciones tecnológicas, así como sus consecuencias, son el punto de partida de algunas propuestas que desde el ámbito de la práctica artística, visibilizan ciertas problemáticas a las que se enfrenta una sociedad marcada por el uso excesivo (abuso) de imágenes y la reiteración de contenidos.

Reproductive costs in terrestrial male vertebrates: insights from bird studies

Reproduction requires resources that cannot be allocated to other functions resulting in direct reproductive costs (i.e. trade-offs between current reproduction and subsequent survival/reproduction). In wild vertebrates, direct reproductive costs have been widely described in females, but their occurrence in males remains to be explored. To fill this gap, we gathered 53 studies on 48 species testing direct reproductive costs in male vertebrates. We found a trade-off between current reproduction and subsequent performances in 29% of the species and in every clade. As 73% of the studied species are birds, we focused on that clade to investigate whether such trade-offs are associated with (i) levels of paternal care, (ii) polygyny or (iii) pace of life. More precisely for this third question, it is expected that fast species (i.e. short lifespan, early maturity, high fecundity) pay a cost in terms of survival, whereas slow species (with opposite characteristics) do so in terms of fecundity. Our findings tend to support this hypothesis. Finally, we pointed out the potential confounding effects that should be accounted for when investigating reproductive costs in males and strongly encourage the investigation of such costs in more clades to understand to what extent our results are relevant for other vertebrates.

Male treefrogs in low condition resume signaling faster following simulated predator attack

Current models indicate that an organism’s sensitivity to risk may be heavily influenced by the trade-off between current and future reproduction. Individuals that have fewer future reproductive opportunities are expected to show more risky behavior as they have less to lose if captured by a predator (the asset protection principle). In this study, we examined the effects of age and physical condition on risk taking behavior during sexual signaling in the gray treefrog (Hyla versicolor) to test the prediction that older and poor condition males will take greater risks than their younger or higher-condition counterparts. In accordance with these predictions, we found that males in low physical condition resumed signaling activity more rapidly following a simulated predator attack than their higher-condition counterparts, although this effect was only apparent in one of two study years. Further, males that resumed calling early did not offset their risk of detection by predators via reduced calling effort. Contrary to our predictions, we did not find age to be a significant predictor of risk taking in male signaling behavior. We conclude with a discussion of possible explanations for the discrepancy observed between years and highlight the potential reproductive consequences of variation in risk taking behavior.

Opposite differential risks for autism and schizophrenia based on maternal age, paternal age, and parental age differences

Effects of maternal and paternal age on offspring autism and schizophrenia risks have been studied for over three decades, but inconsistent risks have often been found, precluding well-informed speculation on why these age-related risks might exist. To help clarify this situation we analysed a massive single population sample from Denmark including the full spectrum of autistic and schizophrenic disorders (eliminating between-study confounding), used up to 30 follow-up years, controlled for over 20 potentially confounding factors and interpret the ultimate causation of the observed risk patterns using generally accepted principles of parent-offspring conflict and life-history theory. We evaluated the effects of paternal age, maternal age and parental age difference on offspring mental disorders and found consistently similar risk patterns for related disorders and markedly different patterns between autistic and schizophrenic disorders. Older fathers and mothers both conferred increased risk for autistic but not schizophrenic disorders, but autism risk was reduced in younger parents and offspring of younger mothers had increased risk for many schizophrenic disorders. Risk for most disorders also increased when parents were more dissimilarly aged. Monotonically increasing autism risk is consistent with mutation accumulation as fathers' age, but this explanation is invalid for schizophrenic disorders, which were not related to paternal age and were negatively correlated with maternal age. We propose that the observed maternally induced risk patterns ultimately reflect a shifting ancestral life-history trade-off between current and future reproduction, mediated by an initially high but subsequently decreasing tendency to constrain foetal provisioning as women proceed from first to final pregnancy.

Heterogeneity in reproductive success explained by individual differences in bite rate and mass change

Allocation of resources to current reproduction may reduce future reproduction, growth, and survival, but individual heterogeneity in resource acquisition may obscure this fitness cost. In capital breeders, heterogeneity in reproductive success is often related to body mass or condition, underlining the importance of stored reserves for reproduction. Heterogeneity in the rate of resource acquisition could also affect reproduction. Resource acquisition depends on food intake, but the effects of individual foraging rate on mass gain and reproductive success in wild herbivorous mammals are unknown. We measured how individual bite rate affected mass change and reproductive success of 55 female eastern gray kangaroos (Macropus giganteus) over 2 years. Females with faster bite rate had greater subsequent mass gain, leading to greater offspring survival. In one of 2 years, bite rate directly increased juvenile survival to 8 months. Bite rate appeared to have a direct effect on survival to weaning for young born to females with above-average mass gain, particularly for females in better body condition. Independent of bite rate, individual mass change explained most of the variation in offspring survival. We found a weak positive effect of body condition on reproductive success, suggesting that condition affected reproductive success through its effect on mass change and bite rate. Kangaroos appeared to combine income and capital breeding strategies to deal with internal and external constraints on resource allocation. Our study underlines the importance of accounting for different sources of individual heterogeneity that may affect trade-offs among life-history traits, with important consequences for population dynamics and the evolution of reproductive strategies.

Social tourism in Russia

Social tourism is one of the most important types of tourism in the system of tourism industry, and a serious impulse is needed for its development and getting attention of the state and business to it. Currently the means of federal and regional budgets decrease by sanatorium treatment of citizens entitled to benefits from year to year. Development of social tourism is absolutely necessary, economically justified and profitable. At current reproduction of human resources is important for social and economic development of territories.

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.

Mating rock shrimp hedge their bets: old males take greater risk, but only after careful assessment of the investment scenario

Mature organisms often have to trade reproductive opportunities against the need to survive, especially in species with exaggerated, sexually selected traits. Life history theory predicts that old males with low residual reproductive value (RRV) would accept greater risk for current reproduction than their younger counterparts. Accordingly, we tested the prediction that, under predation risk, old males of the rock shrimp Rhynchocinetes typus pair with females faster and for a longer time than young males do. We exposed young and old dominant males (in the final ontogenetic stage, called “robustus”) to a female in the absence and presence of a predator. As predicted, older robustus males modified their mating behavior when exposed to a predator. However, in contrast to the prediction, they delayed female seizure under predation risk, possibly to carefully assess the actual threat before initiating female guarding. Once they had established the mate-guarding position, old robustus males did not interrupt it until the end of female spawning and, in the presence of predators, even guarded the female significantly longer than in predator-free treatments. In contrast, younger robustus males did not delay female seizure but abandoned the female repeatedly when a predator was present, suggesting that they perceived and responded to the predation risk. Our results suggest that older robustus males have the experience to assess threats before engaging in risky behaviors that bolster their reproductive success. Although consistent with the theory that low RRV individuals should accept greater reproductive risk, we suggest that old individuals do not recklessly engage in risky behaviors but rather cautiously evaluate the threats before investing in a potentially terminal reproductive event.