Reproductive senescence and terminal investment in female Barbary macaques (Macaca sylvanus) at Salem

The reproductive history of 207 female Barbary macaques, living in a large outdoor enclosure in Southwest Germany, was studied during an 11-year period. The results yielded a significant relationship between female age and fecundity, with fertility rates lower than expected among young and old females. Analysis of the reproductive history of individual females revealed a significant decline in fertility from prime age (7–12 years) to mid age (13–19 years), and from mid age to old age (20–25 years). The proportion of long interbirth intervals increased steadily among aging females. Infant survival was not significantly related to maternal age, but offspring of old females showed the highest survivorship. Behavioral observations revealed that old mothers weaned their offspring significantly later than younger mothers, suggesting that prolongation of interbirth intervals is due not only to deteriorating physical condition but also to increased maternal investment, as life history theory predicts. Reproduction ceased during the middle of the third decade of life. Final cessation of estrous cycling invariably occurred 3 or 4 years after the birth of the last offspring, but a postreproductive life span of 5 years appears to be common in this population. Available data suggest that reproductive senescence and menopause are more common among nonhuman primates than widely believed and that both traits are part of an adaptive life history strategy.     

The song of the old mother: Reproductive senescence in female drosophila

Among animals with multiple reproductive episodes, changes in adult condition over time can have profound effects on lifetime reproductive fitness and offspring performance. The changes in condition associated with senescence can be particularly acute for females who support reproductive processes from oogenesis through fertilization. The pomace fly Drosophila melanogaster is a well-established model system for exploring the physiology of reproduction and senescence. In this review, we describe how increasing maternal age in Drosophila affects reproductive fitness and offspring performance as well as the genetic foundation of these effects. Describing the processes underlying female reproductive senescence helps us understand diverse phenomena including population demographics, condition-dependent selection, sexual conflict, and transgenerational effects of maternal condition on offspring fitness. Understanding the genetic basis of reproductive senescence clarifies the nature of life-history trade-offs as well as potential ways to augment and/or limit female fertility in a variety of organisms.     

The song of the old mother: Reproductive senescence in female drosophila

Among animals with multiple reproductive episodes, changes in adult condition over time can have profound effects on lifetime reproductive fitness and offspring performance. The changes in condition associated with senescence can be particularly acute for females who support reproductive processes from oogenesis through fertilization. The pomace fly Drosophila melanogaster is a well-established model system for exploring the physiology of reproduction and senescence. In this review, we describe how increasing maternal age in Drosophila affects reproductive fitness and offspring performance as well as the genetic foundation of these effects. Describing the processes underlying female reproductive senescence helps us understand diverse phenomena including population demographics, condition-dependent selection, sexual conflict, and transgenerational effects of maternal condition on offspring fitness. Understanding the genetic basis of reproductive senescence clarifies the nature of life-history trade-offs as well as potential ways to augment and/or limit female fertility in a variety of organisms.     

Sex-biased terminal investment in offspring induced by maternal immune challenge in the house wren (Troglodytes aedon)

The reproductive costs associated with the upregulation of immunity have been well-documented and constitute a fundamental trade-off between reproduction and self-maintenance. However, recent experimental work suggests that parents may increase their reproductive effort following immunostimulation as a form of terminal parental investment as prospects for future reproduction decline. We tested the trade-off and terminal investment hypotheses in a wild population of house wrens (Troglodytes aedon) by challenging the immune system of breeding females with lipopolysaccharide, a potent but non-lethal antigen. Immunized females showed no evidence of reproductive costs; instead, they produced offspring of higher phenotypic quality, but in a sex-specific manner. Relative to control offspring, sons of immunized females had increased body mass and their sisters exhibited higher cutaneous immune responsiveness to phytohaemagglutinin injection, constituting an adaptive strategy of sex-biased allocation by immune-challenged females to enhance the reproductive value of their offspring. Thus, our results are consistent with the terminal investment hypothesis, and suggest that maternal immunization can induce pronounced transgenerational effects on offspring phenotypes.     

Reproductive strategies of female butterflies: variation in and constraints on fecundity

ABSTRACT.

• 1 This study first examines the reproductive strategy of female Speyeria mormonia Edwards (Lepidoptera: Nymphalidae):
• 2 Egg weight and number laid per day decrease with age.
• 3 Survival and daily egg number may be affected by temperature; mean daily egg weight is not affected by temperature.
• 4 Daily egg number is not correlated with body size. In the central range of body size, egg weight is also not correlated with body size. However, exceptionally large or small females lay respectively heavier or lighter eggs than average.
• 5 A simple trade-off between offspring size and number does not occur within females on a daily basis, or among females averaged over their lifespans.
• 6 Fat body resources are depleted at a rate independent of body size.
• 7 Females are essentially monogamous.
• 8 Age-specific fecundity data reported here for S.mormonia are next compared with data for other Lepidoptera with different adult feeding habits and egg maturation patterns, and hence different possibilities for adult feeding to play a role in egg production. Based on these comparisons, I propose that the shape of the age-specific fecundity curve for each species under optimal conditions is constrained by the potential importance of adult nutrients in egg production.

     

Dual duplication of neurohypophysial hormones in an Australian marsupial: mesotocin, oxytocin, lysine vasopressin and arginine vasopressin in a single gland of the northern bandicoot (Isoodon macrourus)

Neurohypophysial hormones of an Australian marsupial, the Northern bandicoot (Isoodon macrourus), have been identified by their retention times in high-pressure reverse-phase liquid chromatography using two solvent systems and by their molar pressor or uterotonic activities. Two pressor peptides, arginine vasopressin and lysipressin, and two uterotonic peptides, mesotocin and oxytocin, have been characterized. Because mesotocin and arginine vasopressin have been identified in three other Australian marsupial families, it is assumed that a duplication of each ancestral gene occurred in Peramelidae and subsequent mutations in one copy led to the additional oxytocin and lysipressin. A similar dual duplication of neurohypophysial hormones has previously been discovered in the North-American opossum (Didelphis virginiana) so that the duplication propensity seems peculiar to marsupials in contrast to placental mammals.     

Reproductive effort,fecundity and energy allocation in two species of the genus Perinereis (Polychaeta: Nereididae)

Summary

The reproductive effort in terms of fecundity and energy allocation was studied in two species of semelparous polychaetes belonging to the genus Perinereis, living in the same environment, with different reproductive modalities. There is a great individual variability both in terms of reproductive effort and fecundity. Fecundity varied from 4080 to 15000 oocytes in P. rullieri and from 7000 to 26000 in P. cultrifera; no linear relationship was found between oocyte number and total jaw length utilised as size index. The energy content of germinal and somatic tissues was determined by Differential Scanning Calorimeter (DSC). The reproductive effort was calculated as RE = E_G/(E_G + E_S) where E_G is the total energy in germinal tissues and E_S is the total energy in somatic tissues. Reproductive effort is very high with mean values of 0.62 for P. rullieri and 0.79 for P. cultrifera. The different amounts of energy allocated in germinal tissues can be attributed to the different reproductive modalities—P. rullieri reproduces in the atokous phase whereas P. cultrifera has conserved epitoky in its life-cycle. The lack of correlation between reproductive effort and size index strongly suggests that reproductive allocation does not increase with age. In semelparous species the variability in fecundity and reproductive effort observed cannot be interpreted in terms of a trade-off between fecundity and survival as in iteroparous species. In fact, in semelparous an individual allocates all available resources to reproduction and then dies.     

Effects of maternal age on reproductive traits and fitness components of the offspring in the bruchid beetle, Callosobruchus chinensis (Coleoptera: Bruchidae)

In many insect species, the size and number of eggs decrease with maternal age. Thus, both the size and number of eggs must be considered to know the exact cost of reproduction with maternal age. The resource depletion hypothesis was examined in the bruchid beetle Callosobruchus chinensis. The hypothesis explains why the egg size decreases with maternal age based on the decline of the female's reproductive capacity. A decrease was found in reproductive effort (= egg size × the number of eggs) and the fitness component of offspring with maternal age. The effects of the female's nutritional status on the relationship between maternal age and the reproductive effort of females with and without food and water were also examined. The results indicate that the decrease in size and number of eggs with maternal age can be explained by the resource depletion hypothesis in C. chinensis.     

Influence of resource level on maternal investment in a leaf-cutter bee (Hymenoptera: Megachilidae)

Fisher's (1930) prediction of equal investment for each sexin a panmictic population is influenced by a number of ecologicalfactors, among which resource availability plays a major role,particularly when the population exists under changing resource availability.Rosenheim et al. proposed a multifaceted parental investment modelbased on the underlying assumption that individual females determine theirsex investment according to resource availability and oocyte availabilityto maximize reproductive success. The model predicts that greater availabilityof resources used for provisions will lead to (1) an increasein the proportion of females produced (when the female is thelarger sex) and (2) an increase in the amount of provisionsper offspring and thus an increase in offspring size. I testedthese predictions by a controlled experiment using a leaf-cutterbee, Megachile apicalis. I presented two levels of food resourcesto the nesting females, which were allowed to forage and nestin cages. The experimental results supported these parentalinvestment model's predictions.     

辣椒碱对烟粉虱的生物活性及生长发育和生殖力的影响

在实验室条件下研究了辣椒碱对烟粉虱的生物活性及生长发育和生殖力的影响.结果表明:辣椒碱对烟粉虱各虫态均有杀虫活性,且随辣椒碱浓度的增大活性增强;辣椒碱浸叶法/浸虫法处理对烟粉虱成虫、卵和若虫的毒力(LC50分别为3525.79、1603.29和1526.27mg·L-1))均高于内吸法处理(LC50分别为5360.04、2359.19和5897.43 mg.L-1),两种处理方法下辣椒碱对烟粉虱卵的毒力均明显高于对成虫的毒力;2000和4000 mg·L-1浓度辣椒碱对烟粉虱成虫具有明显的拒食作用,烟粉虱在该两种浓度辣椒碱处理过的棉花叶上取食24 h的蜜露分泌量均显著低于取食非处理棉花叶后的蜜露分泌量;辣椒碱各试验浓度对烟粉虱成虫均表现出较强的产卵忌避作用,当辣椒碱处理浓度达4000 mg·L-1时,对烟粉虱的选择性产卵忌避率和非选择性产卵忌避率分别高达94.2％和83.0％.500、1000和2000 mg·L-1辣椒碱浸渍处理对烟粉虱存活卵和若虫的发育历期、成虫羽化率均没有影响,但辣椒碱4000mg·L-1处理明显延长烟粉虱若虫发育历期、降低成虫羽化率.不同浓度辣椒碱处理均明显抑制烟粉虱生殖力,且这种抑制作用随辣椒碱浓度的增大而增强.     

Condition and reproductive investment in the western mosquitofish (Gambusia affinis): little evidence for condition‐dependent sex‐biased investment

In sexually reproducing species, resources may theoretically be distributed with bias to the production of male or female offspring in response to the condition of the mother, commonly recognized as sex allocation. Using a recently characterized sex‐specific molecular marker, we tested for maternal sex allocation (i.e. maternal primary sex ratio bias and sex‐specific offspring investment) in captive laboratory‐bred western mosquitofish (Gambusia affinis) at early stages of offspring development. We found no statistical evidence to support sex allocation in G. affinis, based on maternal condition. In addition, we found little evidence for correlations between maternal condition and investment in the condition (mass) of individual offspring (of one sex or the other), although we did find that larger mothers tended to have higher fecundity.     

Parthenogenetic female populations in the brown alga Scytosiphon lomentaria (Scytosiphonaceae,Ectocarpales): decay of a sexual trait and acquisition of asexual traits

In isogamous brown algae, the sexuality of populations needs to be tested by laboratory crossing experiments, as the sexes of gametophytes are morphologically indistinguishable. In some cases, gamete fusion is not observed and the precise reproductive mode of the populations is unknown. In the isogamous brown alga Scytosiphon lomentaria in Japan, both asexual (gamete fusion is unobservable) and sexual populations (gamete fusion is observable) have been reported. In order to elucidate the reproductive mode of asexual populations in this species, we used PCR‐based sex markers to investigate the sex ratio of three asexual and two sexual field populations. The markers indicated that the asexual populations consisted only of female individuals, whereas sexual populations are composed of both males and females. In culture, female gametes of most strains from asexual populations were able to fuse with male gametes; however, they had little to no detectable sexual pheromones, significantly larger cell sizes, and more rapid parthenogenetic development compared to female/male gametes from sexual populations. Investigations of sporophytic stages in the field indicated that alternation of gametophytic and parthenosporophytic stages occur in an asexual population. These results indicate that the S. lomentaria asexual populations are female populations that lack sexual reproduction and reproduce parthenogenetically. It is likely that females in the asexual populations have reduced a sexual trait (pheromone production) and have acquired asexual traits (larger gamete sizes and rapid parthenogenetic development).     

Optimal progeny body size in a solitary bee,Osmia bicornis (Apoidea: Megachilidae)

1. Females of solitary, nest‐constructing bees determine both sex (haplo‐diploidy) as well as body size (by amount of provision) of each single offspring. 2. According to the Optimal Allocation Theory, females should allocate resources in portions that maximise fitness returns. A key fitness component in bees is body size that is determined solely by the provisions supplied by the mother. 3. The optimal progeny body size relies on different factors in both sexes. In females, provision efficiency is crucial for reproductive success. In males, however, fitness depends primarily on mating success. 4. Provision efficiency of Osmia bicornis L. females depends on the capacity to stow pollen (scopa) and their ability to carry the packed loads. Scopa capacity increases isometrically with body size whereas indices of flight performance (EPI, free lift) decrease. These complementary effects substantially contribute to the adjustment of optimal body size in daughters. 5. The impact of body mass on fitness of males is determined by the mating system. Owing to the opportunistic polygyny in O. bicornis, there was no detectable correlation between body size and male mating success. Consequently, mother bees distribute their provisions to many, but small sons to increase the number of descendant competitors in the race for matings. Optimal body size in sons is a trade‐off between a large male advantage in rare scrambles over receptive females and small‐size‐related disadvantages in viability.     

Influence of selfing and maternal effects on life-cycle traits and dispersal ability in the herb Hypochaeris radicata (Asteraceae)

The ecological and evolutionary implications of dispersal are many. Pollination type and maternal effects may affect plant fitness traits, including life-cycle traits as well as dispersal ability. This study investigated the joint influence of pollination type and maternal effects on both life-cycle traits and dispersal ability in the herb Hypochaeris radicata . We conducted experimental crosses to obtain selfed and outcrossed progeny. Individual seeds and their pappuses were measured to determine seed terminal velocity. Seed size was also used to assess maternal effects. Selfing dramatically decreased seed set, indicating that H. radicata is self-incompatible. However, the few selfed seeds produced outperformed outcrossed seeds in seed size and flowering probability, surely as a result of an effective reallocation of resources among selfed seeds. None of the life-cycle traits was affected by seed size, the estimate of maternal effects. Selfed seeds were larger and bore a smaller pappus than outcrossed seeds. As a result, dispersal ability was lower for selfed than outcrossed seeds. Several factors, such as the low proportion of plants that produced selfed seeds, the low number of selfed seeds produced per plant, and the lack of self-fertility mechanisms might act in concert to prevent the evolution of selfing in H. radicata .  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 163–170.     

Direct and indirect effects of sexual signal loss on female reproduction in the Pacific field cricket (Teleogryllus oceanicus)

Sexual signal evolution may present fitness consequences for the non‐signaling sex due to shared genes and altered social conditions, but this is rarely studied in natural populations. On the Hawaiian Island of Kauai, most male Teleogryllus oceanicus (Pacific field crickets) lack the ability to sing because of a novel wing mutation (flatwing) that arose and spread in <20 generations. Obligately silent flatwing males have been highly successful because they avoid detection by a deadly, acoustically‐orienting parasitoid fly. Little is known about how the flatwing mutation and resulting song‐less acoustic environment affects female fitness. We found that Kauai females carrying the flatwing allele invested less in reproductive tissues and experienced more instances of mating failure than normal‐wing‐carrying females, though total offspring production did not differ between female genotypes. Females from Oahu (HI, where the parasitoid and flatwing also occur) and Mangaia (an island in the Cook Islands which harbors neither the parasitoid nor flatwing) invested less in reproductive tissues when reared in a song‐less acoustic environment. Kauai females did not exhibit this plasticity, perhaps because they have experienced nearly song‐less conditions for the past ~15 years following the establishment of flatwing. We show that female T. oceanicus experience a mix of costly and beneficial effects of sexual signal loss, which should help maintain the wing polymorphism in the wild. Our results demonstrate that the non‐signaling sex can experience a nuanced set of phenotypic consequences resulting from signal evolution, which can further shape dynamics of sexual signal evolution.     

Yolk androgens in the barn swallow (Hirundo rustica): a test of some adaptive hypotheses

Maternal effects such as androgen in avian eggs can mediate evolutionary responses to selection, allowing manipulation of offspring phenotype and promoting trans-generational adaptive effects. We tested the predictions of two adaptive hypotheses that have been proposed to explain female variation in yolk androgen allocation in birds, using the barn swallow Hirundo rustica as a model. We found no support for the first hypothesis proposing that yolk androgen varies as a function of breeding density in order to prepare offspring for different breeding densities. However, we found experimental support for the hypothesis that female yolk androgen allocation depends on mate attractiveness and that it constitutes an example of differential allocation. Females increased the concentration of androgens in their eggs when mated to males with experimentally elongated tails. Female phenotypic quality as measured by arrival date and clutch size was positively related to egg androgen concentration, consistent with the hypothesis that this is a costly investment, constrained by female condition. We found correlative evidence of a direct relationship between egg androgen concentration and performance of offspring as measured by mass increase.     

Trade-offs between reproductive and somatic (storage) investments in animals: a comparative test of the Van Noordwijk and De Jong model

Classical life-history theory predicts ‘trade-offs’ between reproductive and somatic investments. However, empirical studies have shown that intraspecific phenotypic correlations between these two resource investments are often positive or nonsignificant, rather than negative as predicted. The model of Van Noordwijk and De Jong (1986) was proposed to explain these unexpected results. According to their model, positive correlations between reproductive and somatic investments will result if individual variation in resource acquisition exceeds that of resource allocation, whereas negative correlations will result if individual variation in resource allocation exceeds that of resource acquisition. To test this model, I used body storage/condition as an index of somatic investment because it is usually strongly related to level of resource acquisition. I predicted that laboratory studies should more often show negative correlations between reproductive and somatic investments than field studies, because individual variation in resource acquisition is expected to be lower in controlled laboratory environments than in variable natural environments. A literature review revealed that correlations between somatic (storage) investment and reproductive investment (estimated as clutch/litter mass, number of offspring per clutch/litter, or number of clutches/litters) among conspecific breeding female animals are more often positive (15 species) or nonsignificant (17 species) than negative (6 species). Moreover, as expected, five of six negative correlations were observed in laboratory studies, whereas 13 of 15 positive correlations were observed in field studies. It is concluded that future empirical and theoretical work on life histories should consider individual variation in both resource acquisition and allocation and the interaction between the two. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of delayed fertilization on embryo viability in walleye Sander vitreus (Mitchill): the role of maternal effects

The effects of delayed fertilization on embryonic viability in walleye Sander vitreus were examined using laboratory fertilization and incubation trials. Both fertilization success (survival to 10 h post-fertilization) and embryonic survival (from 10 to 168 h post-fertilization) generally declined with increasing ova storage time but trends varied significantly among females. Embryonic survival of individual egg batches was positively related to fertilization success. The slope of the relationship between fertilization success and ova storage time was negatively related to maternal fork length indicating that ova quality declined more rapidly with storage time for larger females than for smaller females. In contrast, the slope of the early embryonic survival v. ova storage time relationship was not significantly related to maternal size.     

The neighborhood matters: effects of neighbor number and sibling (or kin) competition on floral traits in Spergularia marina (Caryophyllaceae)

Abstract.— Effects of abiotic factors on the expression of floral and gender traits have been well documented in wild plant species; by contrast, little is known of the effect(s) on an individual's floral phenotype of the genetic composition of its neighboring conspecifics. Here we report the results of a greenhouse experiment conducted to detect the effects of genetic attributes of an individual's local environment on the expression of floral traits in the selfing annual, Spergularia marina (Caryophyllaceae). First, to test the hypothesis that negative effects of intraspecific competition are stronger when an individual competes with genetically similar individuals than when it competes with unrelated genotypes, we evaluated the effects of the number of nearest-neighbor kin (vs. unrelated individuals) on floral traits. Plants adjacent to two kin produced significantly fewer stamens per flower than plants adjacent to one or no siblings, indicating that kin competition reduced allocation to male function. Second, to test the hypothesis that the genetic diversity of a neighborhood influences the phenotype of a focal plant, we determined whether the number of maternal families represented among an individual's nearest neighbors influences its phenotype. The number of maternal families surrounding a focal plant did not affect floral trait expression. These results suggest that in S. marina , male function is more sensitive than female function to the genetic environment and that as an individual's genetic similarity to its neighbors increases, so do the negative effects of competition for limited resources.     

The effect of ejaculate mass on female reproductive output in the european swallowtail butterfly,Papilio machaon (L.) (Lepidoptera: Papilionidae)

Previously, we showed that virgin males of Papilio machaondeliver ejaculates that are twice as big as any ejaculates they transfer at later matings. Here, we investigate the consequences of these two size classes of ejaculates on female reproductive output and demonstrate that females that received one small ejaculate laid as many eggs, fertilized the same proportion of eggs, and lived as long as those that had received one big ejaculate. However, females that received big ejaculates laid heavier eggs, but only between the twelfth and the fifteenth days of egg-laying. We conclude that male-derived nutrients appear to have a limited effect on female reproductive output in P. machaonand that the large size of ejaculates delivered by male butterflies are determined primarily by selection on males to produce longer refractory periods in females.