Reproductive Trade-offs Research Articles

Intraspecific Variation in Parental Care May Reflect Variation in Parental Quality.

The existence of life-history trade-offs is a fundamental assumption of evolutionary biology and behavioural ecology, yet empirical studies have found mixed evidence for this. Such trade-offs are expected when individuals vary in how they allocate their limited resource budgets between different life-history functions (variation in resource allocation), but they may be masked when individuals vary in how many resources they have acquired that they can later allocate to life-history functions (variation in resource acquisition). We currently lack studies on the extent to which individual differences in behaviour reflect variation between individuals in resource acquisition and resource allocation. Here, we use parental care as a case study for exploring this question. We used the burying beetle Nicrophorus vespilloides, which exhibits facultative biparental care, comprising direct care (provisioning food or interacting with larvae) and indirect care (guarding or maintaining the carcass). We found some evidence for a positive relationship between these two components of care for both male and female parents. In addition, parents that spent more time providing care 24 h after hatching also tended to provide care for longer. Lastly, parents that provided more parental care did not experience a trade-off of reduced lifespan after the breeding attempt. On the contrary, we found a positive relationship between the duration of care provided and parents' post-breeding lifespan. Our finding of positive relationships between parental behaviours and between parental care and lifespan suggests that variation in care was mainly driven by differences in prior resource acquisition (i.e., parental quality) among individuals rather than differences in resource allocation. Our findings thus suggest that high intraspecific variation in parental quality can potentially mask reproductive investment trade-offs within populations.

High-quality dietary protein (essential amino acids matched to reproductive needs) partially breaks the lifespan and reproduction trade-off in lubber grasshoppers.

Finding interventions to break the trade-off between reproduction and lifespan can provide insight into physiological limitations of animals. Effects of dietary protein quality on the trade-off are currently unclear, but clarity could lead to better designed diets that match animal needs. Dietary amino acid blends matching yolk proteins support reproduction and extend lifespan in fruit flies. To test if this is conserved across species, we matched dietary amino acids to vitellogenin to test reproduction and lifespan in adult females of the lubber grasshopper. Specifically, we compared varying degrees of protein quality by manipulating dietary essential amino acids. We identified a high-quality protein diet (amino acids matched to vitellogenin, or reproductive needs) that increased reproduction and matched lifespan in comparison to diets that differed only in the ratios of essential amino acids (i.e., were isocaloric and isonitrogenous). All these diets had longer lifespan but lower reproductive output than fully fed controls. In a separate experiment, full reproduction was possible on the high-quality artificial diet when offered at a 78% higher protein quantity and with a larger lettuce supplement (~ 17% of ad libitum). Additionally, we observed that as dietary protein quality was decreased (i.e., diets were less matched to vitellogenin), reproduction was reduced, and lifespan was extended in the more extreme scenarios. Taken together, these results indicate that the balance of dietary essential amino acids plays an important role in the lifespan and reproduction trade-off, while more work needs to be conducted to find the optimal diet mix for this species.

Finding a balance: Reproductive trade-offs in parasitic isopods of the family Cymothoidae.

In this study conducted along the coast of Odisha, India, reproductive trade-offs in isopods of the family Cymothoidae were investigated, focusing on the relationship between the number vs. volume of eggs and the percentage of brood to body volume. Ovigerous females from species with substantial sample sizes (n > 30) were analyzed to understand their survival strategies. The findings highlight distinct strategies among different parasite types within Cymothoidae. Buccal parasites such as Cymothoa frontalis and Cymothoa indica, along with branchial parasites like Joryma sawayah and Agarna malayi, generally produced a higher number of smaller eggs, except for A. malayi, which produced fewer but larger eggs. In contrast, the external body surface-attaching parasite, Nerocila orbignyi, was observed to produce fewer eggs of larger size. Across all parasite types (intraspecific), there was a statistically significant negative correlation between egg number and egg volume (p < 0.05). Buccal parasites were observed to have the highest percentage of marsupium volume relative to body volume, indicating a strategy to maximize egg storage. Conversely, external body surface-attaching parasites had the lowest percentage, possibly reflecting adaptation to a different reproductive environment. Additional observations revealed anatomical adaptations in all the studied isopod species which include the shift of the alimentary canal to the dorsal side to accommodate the development of the marsupial sac for egg incubation. In summary, these findings illustrate how parasitic isopods of the family Cymothoidae manage trade-offs between reproductive potential and success, crucial for their species' continuity and survival strategies in coastal ecosystems.

Increased Reproductive Output and Telomere Shortening Following Calcium Supplementation in a Wild Songbird.

Life history theory predicts increased parental investment comes with fitness costs, often expressed as negative effects on survival and future reproduction. To better understand the costs of reproduction and life history trade-offs, we evaluated calcium supplementation at a high-elevation site in Colorado as a novel approach to experimentally alter reproductive investment in nesting female Tachycineta bicolor (tree swallow). Calcium is a nutrient critical to avian reproduction as the intake of natural calcium is essential for egg production, embryo development, and nestling growth. Altering calcium availability exclusively during the breeding season allowed examination of individual biological responses to experimental modification of reproduction, as well as the reproductive costs associated with egg production and laying an entire clutch. As a functional endpoint and proxy for fitness and longevity, telomere length was measured at the beginning and end of each breeding season. Telomeres-protective "caps" at the ends of chromosomes-have been shown to shorten with aging and a variety of stressors, including higher reproductive output. Results demonstrate that tree swallow mothers supplemented with calcium during the breeding season experience higher reproductive output and produce offspring with longer telomeres, which came at the cost of relatively shorter telomeres during the reproductive season. These findings provide additional support for reproductive trade-offs, and also challenge previous calcium supplementation studies that suggest excess calcium reduces the cost of reproduction.

Cumulative and interannual effects of reproduction in eastern grey kangaroos.

Reproduction can reduce energy allocation to other life-history traits such as survival and growth. Resource constraints give rise to (co)variation in life-history traits and to heterogeneity in energy acquisition and allocation. At each reproductive opportunity, females face a choice between allocation to current reproduction or to maintenance. Many studies compare reproductive trade-offs between two consecutive years, but few account for the cumulative effects of reproduction over multiple years, a crucial factor in understanding life-history evolution in long-lived iteroparous species. We compared short- (interannual) and long-term (cumulative) reproductive trade-offs with a 14-year capture-mark-recapture study of eastern grey kangaroos, where females can have substantial skeletal growth for several years after maturation. We used a multivariate approach to compare how interannual and multi-annual cumulative reproduction affected growth (n = 378 measurements), mass change (n = 376 measurements) and subsequent reproduction (n = 388 measurements), and to quantify (co)variation between these traits among individuals (n = 107) and years (n = 14). Interannually, young females that reproduced experienced decreased skeletal growth compared to young females that did not reproduce. Reproductive females of all ages experienced reduced mass gain and weaning probability in the following year. The cumulative effects of multiple reproductions included decreased skeletal growth, mass gain and weaning probability in the following year. These effects increased with age and reproductive rate. We found positive trait correlations between mass change, leg growth and subsequent reproduction among individuals and years, though weaker at the cumulative than interannual level. Females experience dynamic interannual and cumulative trade-offs. Our analyses of cumulative costs of reproduction revealed long-term trade-offs as well as cumulative costs that were not apparent when estimating interannual costs. Trait correlations suggested heterogeneity in growth and reproduction among females. Years of increased growth were followed by years of increased reproduction, and years of poor growth were followed by years of poor reproduction. Our exploration of both interannual and cumulative costs of reproduction underscores the need to account for long-term reproductive histories to better understand reproductive trade-offs in long-lived iteroparous species.

Common viral infections inhibit egg laying in honey bee queens and are linked to premature supersedure

With their long lives and extreme reproductive output, social insect queens have escaped the classic trade-off between fecundity and lifespan, but evidence for a trade-off between fecundity and immunity has been inconclusive. This is in part because pathogenic effects are seldom decoupled from effects of immune induction. We conducted parallel, blind virus infection experiments in the laboratory and in the field to interrogate the idea of a reproductive immunity trade-off in honey bee (Apis mellifera) queens and to better understand how these ubiquitous stressors affect honey bee queen health. We found that queens injected with infectious virus had smaller ovaries and were less likely to recommence egg-laying than controls, while queens injected with UV-inactivated virus displayed an intermediate phenotype. In the field, heavily infected queens had smaller ovaries and infection was a meaningful predictor of whether supersedure cells were observed in the colony. Immune responses in queens receiving live virus were similar to queens receiving inactivated virus, and several of the same immune proteins were negatively associated with ovary mass in the field. This work supports the hypothesized relationship between virus infection and symptoms associated with queen failure and suggests that a reproductive-immunity trade-off is partially, but not wholly responsible for these effects.

Cumulative costs of reproduction in a long-lived ungulate

Abstract Cumulative costs of reproduction are predicted by life-history theories of aging, but empirical support for cumulative costs of reproduction in ungulates is limited. Examinations of the relationship between previous reproductive effort and future reproductive output are often limited to successive years. We analyzed pregnancy status, lactation duration, and age class of Elk (Cervus canadensis) in Utah, United States, from 2019 to 2022 to better understand the relationship between previous reproductive effort and future reproductive output, particularly in nonsuccessive years. Pregnancy status 1 year prior, pregnancy status 2 years prior, and age had no effect on the likelihood of pregnancy in Elk. However, lactation duration 1 year prior and lactation duration 2 years prior had a negative effect on the likelihood of pregnancy. The best-fitting model to explain the relationship between pregnancy status and previous lactation was the positive interaction between lactation duration 1 year prior and lactation duration 2 years prior. The results of our study suggest long-lasting (i.e., multiple-year), cumulative costs of reproduction can influence reproductive output in female Elk, but differences in individual quality may have an even greater influence. High-quality individuals may be able to override the costs of reproduction and minimize reproductive trade-offs.

A role of epigenetic mechanisms in regulating female reproductive responses to temperature in a pest beetle.

Many species are threatened by climate change and must rapidly respond to survive in changing environments. Epigenetic modifications, such as DNA methylation, can facilitate plastic responses by regulating gene expression in response to environmental cues. Understanding epigenetic responses is therefore essential for predicting species' ability to rapidly adapt in the context of global environmental change. Here, we investigated the functional significance of different methylation-associated cellular processes on temperature-dependent life history in seed beetles, Callosobruchus maculatus Fabricius 1775 (Coleoptera: Bruchidae). We assessed changes under thermal stress in (1) DNA methyltransferase (Dnmt1 and Dnmt2) expression levels, (2) genome-wide methylation and (3) reproductive performance, with (2) and (3) following treatment with 3-aminobenzamide (3AB) and zebularine (Zeb) over two generations. These drugs are well-documented to alter DNA methylation across the tree of life. We found that Dnmt1 and Dnmt2 were expressed throughout the body in males and females, but were highly expressed in females compared with males and exhibited temperature dependence. However, whole-genome methylation did not significantly vary with temperature, and only marginally or inconclusively with drug treatment. Both 3AB and Zeb led to profound temperature-dependent shifts in female reproductive life history trade-off allocation, often increasing fitness compared with control beetles. Mismatch between magnitude of treatment effects on DNA methylation versus life history effects suggest potential of 3AB and Zeb to alter reproductive trade-offs via changes in DNA repair and recycling processes, rather than or in addition to (subtle) changes in DNA methylation. Together, our results suggest that epigenetic mechanisms relating to Dnmt expression, DNA repair and recycling pathways, and possibly DNA methylation, are strongly implicated in modulating insect life history trade-offs in response to temperature change.

A test of trade-offs in dispersal and reproduction within and between a sister species pair of specialist insect herbivores.

Understanding the drivers of trade-offs among traits is vital for comprehending the evolution and maintenance of trait variation. Theoretical frameworks propose that evolutionary mechanisms governing trade-offs frequently exhibit a scale-dependent nature. However, empirical tests of whether trade-offs exhibited across various biological scales (i.e. individuals, populations, species, genera, etc.) remains scarce. In this study, we explore trade-off between dispersal and reproductive effort among sympatric sister species of wasps in the genus Belonocnema (Hymenoptera: Cynipini: Cynipidae) that form galls on live oaks: B. fossoria, which specializes on Quercus geminata, and B. treatae, which specializes on Q. virginiana. Specifically, our results suggest that B. fossoria has evolved reduced flight capability and smaller wings, but a larger abdomen and greater total reproductive effort than B. treatae, which has larger wings and is a stronger flier, but has a smaller abdomen and reduced total reproductive effort. These traits and the relationships among them remain unchanged when B. fossoria and B. treatae are transplanted and reared onto the alternative host plant, suggesting that trait divergence is genetically based as opposed to being a plastic response to the different rearing environments. However, when looking within species, we found no evidence of intraspecific trade-offs between wing length and reproductive traits within either B. fossoria or B. treatae. Overall, our results indicate that observed trade-offs in life history traits between the two gall former species are likely a result of independent adaptations in response to different environments as opposed to the amplified expression of within species intrinsic tradeoffs.

The Human Capital–Reproductive Capital Trade-Off in Marriage Market Matching

Previous articleNext article No AccessThe Human Capital - Reproductive Capital Tradeoff in Marriage Market MatchingCorinne LowCorinne Low Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmailPrint SectionsMoreDetailsFiguresReferencesCited by Journal of Political Economy Just Accepted Article DOIhttps://doi.org/10.1086/726238 HistoryAccepted May 23, 2023 © 2023 The University of Chicago. All Rights reserved.PDF download Crossref reports no articles citing this article.

Low haemoglobin in arduous seasons is associated with reduced chance of ovulation among women living in the Bolivian altiplano.

Female reproductive function flexibly responds to ecological variation in energy availability, but the roles of other ecologically limited resources, such as iron, remain poorly understood. This analysis investigates whether haemoglobin associates with investment in reproductive function in a rural natural fertility population living in the Bolivian altiplano. We conducted a cross-sectional secondary analysis of prospectively collected biomarker and sociodemographic data, comprising 152 menstrual cycles from 96 non-contracepting women living at 3800 m altitude. Multivariable multilevel models were used to investigate (i) whether haemoglobin concentration is associated with ecological variation in subsistence strategy and seasonal conditions, and (ii) whether haemoglobin concentration is associated with the occurrence of ovulation and/or the concentration of luteal progesterone, two biomarkers of current investment in reproduction. Haemoglobin concentrations were lower in arduous seasons among those women more dependent on traditional agropastoral subsistence strategies (β = -0.42, 95% CI: -0.80 to -0.04, P = 0.032). During more arduous seasons, a 1 standard deviation increase in haemoglobin was associated with an over 3-fold increase in the odds of ovulation after adjusting for body fat, breastfeeding status, and age (adjusted odds ratio = 3.27, 95% CI: 1.10 to 9.27, P = 0.033). When conditions are relatively harsh and may be expected to improve, low haemoglobin levels are associated with lower current investment in reproduction and reduced fecundity. These results support the role of iron, independent of energy stores, as a limiting resource in modulating reproductive trade-offs.

Trade-offs in growth and reproduction of rhizomatous clonal plant Phragmites communis in response to aeolian processes

Abstract Trade-offs in growth and reproduction are essential parts of the adaptive strategies of clonal plants. How rhizomatous psammophytes respond to aeolian processes (sand burial and wind erosion) by means of trade-offs is supposed to be especially important for their colonization on the active sand dune. Despite partial documentation of the responses of rhizomatous species to aeolian processes, how these clonal species respond to aeolian processes by means of potential trade-offs in growth and reproduction still remains unclear. In this study, we employed field investigation and biomass modeling to evaluate the trade-offs between vegetative and reproductive growth as well as between the number and size of ramets of Phragmites communis in response to sand burial and wind erosion. Sand burial enhanced the accumulation of seed biomass and reproductive effort. Wind erosion reduced reproductive effort but had no significant influence on seed biomass. Sand burial increased the biomass of ramets, while wind erosion increased ramet population density and accelerated ramet maturation. Our results demonstrate that rhizomatous psammophytes adjust their growth strategies in response to aeolian processes, i.e. reproductive growth and ramet size increase in response to sand burial, while vegetative growth and ramet numbers increase in response to wind erosion.

Physiological and behavioral basis of diamondback moth Plutella xylostella migration and its association with heat stress.

Migration is a strategy that shifts insects to more favorable habitats in response to deteriorating local environmental conditions. The ecological factors that govern insect migration are poorly understood for many species. Plutella xylostella causes great losses in Brassica vegetable and oilseed crops, and undergoes mass migration. However, the physiological and behavioral basis for distinguishing migratory individuals and the factors driving its migration remain unclear. Daily light trap catches conducted from April to July in a field population of P. xylostella in central China revealed a sharp decline in abundance from late-May. Analysis of ovarian development levels showed that the proportion of sexually immature females gradually increased, while the mating rate decreased, indicating that generations occurring in May mainly resulted from local breeding and that emigration began in late-May. Physiological and behavioral analyses revealed that emigrant populations had a higher take-off proportion, stronger flight capacity and greater energy reserves of triglyceride compared to residents. Furthermore, a gradual increase in temperature from 24 °C to >30 °C during larval development resulted in a significant delay in oogenesis and increased take-off propensity of adults compared with the control treatment reared at a constant temperature of 24 °C. Our results provide the physiological and behavioral factors that underpin mass migration in P. xylostella, and demonstrate that exposure to increased temperature increases their migration propensity at the cost of reproductive output. This study sheds light on understanding the factors that influence population dynamics, migratory propensity and reproductive tradeoffs in migratory insects. © 2023 Society of Chemical Industry.

Trait-dependent associations between early- and late-life reproduction in a wild mammal.

Early- versus late-life trade-offs are a central prediction of life-history theory that are expected to shape the evolution of ageing. While ageing is widely observed in wild vertebrates, evidence that early-late trade-offs influence ageing rates remains limited. Vertebrate reproduction is a complex, multi-stage process, yet few studies have examined how different aspects of early-life reproductive allocation shape late-life performance and ageing. Here, we use longitudinal data from a 36-year study of wild Soay sheep to show that early-life reproduction predicts late-life reproductive performance in a trait-dependent manner. Females that started breeding earlier showed more rapid declines in annual breeding probability with age, consistent with a trade-off. However, age-related declines in offspring first-year survival and birth weight were not associated with early-life reproduction. Selective disappearance was evident in all three late-life reproductive measures, with longer-lived females having higher average performance. Our results provide mixed support for early-late reproductive trade-offs and show that the way early-life reproduction shapes late-life performance and ageing can differ among reproductive traits.

Tradeoffs explain scaling, sex differences, and seasonal oscillations in the remarkable weapons of snapping shrimp (Alpheus spp.).

Evolutionary theory suggests that individuals should express costly traits at a magnitude that optimizes the trait bearer's cost-benefit difference. Trait expression varies across a species because costs and benefits vary among individuals. For example, if large individuals pay lower costs than small individuals, then larger individuals should reach optimal cost-benefit differences at greater trait magnitudes. Using the cavitation-shooting weapons found in the big claws of male and female snapping shrimp, we test whether size- and sex-dependent expenditures explain scaling and sex differences in weapon size. We found that males and females from three snapping shrimp species (Alpheus heterochaelis, Alpheus angulosus, and Alpheus estuariensis) show patterns consistent with tradeoffs between weapon and abdomen size. For male A. heterochaelis, the species for which we had the greatest statistical power, smaller individuals showed steeper tradeoffs. Our extensive dataset in A. heterochaelis also included data about pairing, breeding season, and egg clutch size. Therefore, we could test for reproductive tradeoffs and benefits in this species. Female A. heterochaelis exhibited tradeoffs between weapon size and egg count, average egg volume, and total egg mass volume. For average egg volume, smaller females exhibited steeper tradeoffs. Furthermore, in males but not females, large weapons were positively correlated with the probability of being paired and the relative size of their pair mates. In conclusion, we identified size-dependent tradeoffs that could underlie reliable scaling of costly traits. Furthermore, weapons are especially beneficial to males and burdensome to females, which could explain why males have larger weapons than females.

Nitrogen addition promotes terrestrial plants to allocate more biomass to aboveground organs: A global meta-analysis.

A significant increase in reactive nitrogen (Nr) added to terrestrial ecosystems through agricultural fertilization or atmospheric deposition is considered to be one of the most widespread drivers of global change. Modifying biomass allocation is one primary strategy for maximizing plant growth rate, survival, and adaptability to various biotic and abiotic stresses. However, there is much uncertainty as to whether and how plant biomass allocation strategies change in response to increased nitrogen inputs in terrestrial ecosystems. Here, we synthesized 3,516 paired observations of plant biomass and their components related to nitrogen additions across terrestrial ecosystems worldwide. Our meta-analysis reveals that N addition (ranging from 1.08 to 113.81 g m-2 yr-1 ) increased terrestrial plant biomass by 55.62% on average. Nitrogen addition has increased plant stem mass fraction, shoot mass fraction, and leaf mass fraction by 13.8%, 12.9%, and 13.4%, respectively, but with an associated decrease in plant reproductive mass (including flower and fruit biomass) fraction by 3.4%. We further documented a reduction in plant root-shoot ratio and root mass fraction by 27% (21.8-32.1%) and 14.7% (11.6-17.8%), respectively, in response to N addition. Meta-regression results showed that N addition effects on plant biomass were positively correlated with mean annual temperature, soil available phosphorus, soil total potassium, specific leaf area, and leaf area per plant. Nevertheless, they were negatively correlated with soil total nitrogen, leaf carbon/nitrogen ratio, leaf carbon and nitrogen content per leaf area, as well as the amount and duration of nitrogen addition. In summary, our meta-analysis suggests that N addition may alter terrestrial plant biomass allocation strategies, leading to more biomass being allocated to aboveground organs than belowground organs and growth vs reproductive trade-offs. At the global scale, leaf functional traits may dictate how plant species change their biomass allocation pattern in response to nitrogen addition.

Coming of age: Annual onset of coral reproduction is determined by age rather than size

Constraints on organisms possessing a unitary body plan appear almost absent from colonial organisms. Like unitary organisms, however, coral colonies seemingly delay reproduction until reaching a critical size. Elucidating ontogenetic processes, such as puberty and aging are complicated by corals' modular design, where partial mortality and fragmentation lead to distortions in colony size-age relationships. We explored these enigmatic relations and their influence on reproduction by fragmenting sexually mature colonies of five coral species into sizes below the known size at first reproduction, nurturing them for prolonged periods, and examining their reproductive capacity and trade-offs between growth rates and reproductive investment. Most fragments were reproductive regardless of their size, and growth rates hardly affected reproduction. Our findings suggest that once the ontogenetic milestone of puberty is reached, corals retain reproductive capacity irrespective of colony size, highlighting the key role that aging may have in colonial animals, which are commonly considered non-aging.

Anthropogenic impacts on threatened species erode functional diversity in chelonians and crocodilians

The Anthropocene is tightly associated with a drastic loss of species worldwide and the disappearance of their key ecosystem functions. The orders Testudines (turtles and tortoises) and Crocodilia (crocodiles, alligators, and gharials) contain numerous threatened, long-lived species for which the functional diversity and potential erosion by anthropogenic impacts remains unknown. Here, we examine 259 (69%) of the existing 375 species of Testudines and Crocodilia, quantifying their life history strategies (i.e., trade-offs in survival, development, and reproduction) from open-access data on demography, ancestry, and threats. We find that the loss of functional diversity in simulated extinction scenarios of threatened species is greater than expected by chance. Moreover, the effects of unsustainable local consumption, diseases, and pollution are associated with life history strategies. In contrast, climate change, habitat disturbance, and global trade affect species independent of their life history strategy. Importantly, the loss of functional diversity for threatened species by habitat degradation is twice that for all other threats. Our findings highlight the importance of conservation programmes focused on preserving the functional diversity of life history strategies jointly with the phylogenetic representativity of these highly threatened groups.

How does the timing of weapon loss influence reproductive traits and trade-offs in the insect Narnia femorata?

A longstanding goal of evolutionary biology is to understand among-individual variation in resource allocation decisions and the timing of these decisions. Recent studies have shown that investment in elaborate and costly weapons can result in trade-offs with investment in testes. In this study, we ask the following questions: At what point plasticity in resource allocation to these different structures ceases during development, if at all? Furthermore, can individuals tailor their reproductive behavior to accompany structural changes? We experimentally addressed these questions in the insect Narnia femorata, quantifying resource reallocation across development for the first time, using a phenotypic engineering approach. To investigate whether allocation plasticity diminishes throughout ontogeny, we induced weapon loss at a range of different developmental stages and examined subsequent testes mass and reproductive behavior. We found that relative testes mass increased as weapon investment decreased, implying a direct trade-off between testes and weapon investment. However, autotomy postadulthood ceased to induce larger testes mass. Intriguingly, losing a weapon while young was associated with extended adult mating duration, potentially enabling compensation for reduced fighting ability. Our results highlight the importance of examining the ontogeny of trade-offs between reproductive traits and the flexibility of the relationship between reproductive morphology and behavior.

Lactation attenuates pro-oxidant reactions in the maternal brain

Reactive oxygen species (ROS) are intimately linked to bioenergetics and redox biology, contributing to cellular functioning and physiological signaling, but also acting as toxic agents during oxidative stress. Hence, the balance between pro-oxidant reactions and the activity of antioxidant defenses sustains a basal oxidative status, controls the increase of redox signaling, and mediates potential pathological events during oxidative stress. Maternal experience, especially during nursing, requires high energetic demands and expenditure to ensure the well-being of the offspring. The mother must adapt from satisfying her own needs to additionally fulfilling those of her descendants. Oxidative stress has been proposed as one of the reproductive trade-off hallmarks. However, the oxidative shielding hypothesis has also been proposed in the context of reproduction. The reproductive experience induces a wide range of well-documented changes in the female brain, which potentially lead to protection against the enhanced oxidative activity. To date, the metabolic and cellular mechanisms that underlie lactation-induced neuroprotection against oxidants are unknown. The neuroendocrine changes in the brain of the lactating dam promote diminished propensity to excitotoxic brain injury and stress, as well as enhanced neuroprotection and plasticity. In addition to review studies on the oxidant balance due to motherhood, we included new data from our laboratory, addressing the importance of measuring pro-oxidant reactions in separated brain regions. The hippocampus of lactating rats exhibits lower levels of pro-oxidant reactions than that of virgin rats, supporting the oxidative shielding hypothesis in lactation.