Maternal effort and male quality in the bank vole, Clethrionomys glareolus.

Parental investment in reproduction is adjusted according to potential benefits in terms of offspring survival and/or mating success. If male quality affects the reproductive success of a female, then females mating with high-quality males should invest more in reproduction. Although the subject has been of general interest, further experimental verification of the hypothesis is needed. We studied whether female bank voles (Clethrionomys glareolus) adjusted their maternal effort according to male quality, measured as mating success. To enable the measurement of maternal effort during nursing separately from male genetic effects the litters were cross-fostered. Further, the genetic background of male quality was examined. Male quality did not correlate with litter size or offspring size at birth. Offspring growth was positively related to food consumption and milk production of mothers. However, these direct measurements of maternal effort were independent of male quality. Male mating success appeared to be significantly heritable indicating that there are genetic benefits. Still, females did not adjust maternal effort according to the genetic quality of their offspring. We suggest that female bank voles gain significant genetic benefits from mating with high-quality males whereas they cannot improve their reproductive success by increasing maternal effort.     

Food Deprivation and Restriction During late Gestation Affect the Sexual Behavior of Postpartum Female Meadow Voles,Microtus pennsylvanicus

In many species of small mammals, including meadow voles, Microtus pennsylvanicus, females come into postpartum estrus (PPE) within 12–24 h of giving birth, allowing them to mate and become pregnant while raising the current litter. PPE females show increases in attractivity, proceptivity, and receptivity, the three components of sexual behavior, relative to females not in PPE. Several studies have shown that food deprivation and restriction reduce attractivity, proceptivity, and receptivity of females not in PPE. We tested the hypothesis that food deprivation and restriction during late gestation cause deficits and decrease the attractivity, proceptivity, and receptivity of females when they enter PPE. Our data support the hypothesis. On day 1 of lactation, females that were food deprived and food restricted produced scent marks that were significantly less attractive as those produced by control PPE females. Food deprivation but not food restriction caused females to no longer display significant preferences for the scent marks of males over those of females (proceptivity). Food deprivation and food restriction were sufficient to induce females to become significantly less sexually receptive than control females. Eleven of 12 control PPE females mated, 4 of 12 food‐restricted females mated, and 3 of 12 food‐deprived females mated. Dams facing food deprivation or restriction during late gestation may have to balance the benefits of mating during PPE with the increased costs associated with getting pregnant while they are lactating.     

Female Gryllus vocalis Field Crickets Gain Diminishing Returns from Increasing Numbers of Matings

Although female insects generally gain reproductive benefits from mating frequently, females do not mate unlimited numbers of times. This study asks whether the limit on female mating rate is imposed by trade‐offs between reproduction and survival. Female Gryllus vocalis were given the opportunity to mate 5, 10, or 15 times with novel males, and the effects on daily fecundity (egg production), fertility (proportion of eggs that were fertilized), and female post‐experimental longevity were measured. Females that mated 10 times laid more eggs and had a higher proportion of fertile eggs than females that mated 5 times. However, females that mated 15 times did not lay significantly more eggs or have a higher proportion of fertile eggs than females that mated 10 times. Although number of matings did not affect the date that females laid their last egg, mating more times was associated with a prolonged period of laying fertile eggs. Number of matings did not affect female post‐experimental longevity. Thus, there was no trade‐off between female reproductive effort and survival, even when females mated very large numbers of times. When females were allowed to mate ad libitum, the average number of times that females mated was greater than the number of times that confers maximal fitness. The lack of cost to mating explains why females might be willing to mate beyond the point of diminishing reproductive returns.     

圈养猞猁多雄交配雄性的成功繁殖

研究了笼养猞猁多雄交配的结果以及雄性的成功繁殖。雄兽与发情雌兽随机配对,其繁殖成功(所产生的后代数量)不取决于与雌兽的交配顺序、交配次数与持续时间、遗传关系或雄兽的行为特征,但似乎取决于精子质量,特别是取决于形态正常精子的百分率。繁殖成功的雄兽比其竞争对手具有更多的形态正常的精子,似乎更能成功地诱发交配雌兽的排卵。证实了4窝(占总窝数的20%)幼兽的双重父亲身份。在所有情形下, 2雄1雌的交配间隔为24h 。     

Reproductive responses to variation in temperature and food supply by house mice: II. Lactation

Lactating HS/Ibg house mice housed at 21 degrees C and 5 degrees C were assigned to 3 feeding regimes: ad libitum, daily rations of 80% of ad libitum, or 60% of ad libitum beginning on the day that they bore litters. Significant interaction between temperature and food restriction was found for litter survivorship, pup survivorship, litter size, female body weight, and cumulative biomass production. The interaction was due to a magnification of the effects of food restriction at the colder temperature: i.e. mice fed ad libitum were similar at the two temperatures, mice fed the 80% ration differed, and mice fed the 60% ration differed to a greater extent. The dominant response to food restriction was cannibalism by females, which might be associated with the rate of loss in body weight by the female on the days preceding cannibalism of one or more pups. Incidents of cannibalism tended to involve a limited number of pups and to be repeated until a sustainable litter size was reached. In 3 of the food-restricted treatments, females weaned relatively large litters of relatively small pups, but in the most severe treatment (in the group fed the 60% ration at 5 degrees C), the females weaned small litters of large pups. The patterns of cannibalism and variable relative investment in individual pups reflect the aggressive breeding strategy of this classic colonizing species.     

A cost of maternal care in the dung beetle Onthophagus taurus?

Parental care theory assumes that investment in current offspring will trade against future investment. A number of field studies on birds have used clutch size manipulations to demonstrate a survival cost to chick rearing. However, such studies do not account for costs accrued during earlier stages of reproduction because not all aspects of reproductive effort are manipulated by varying the number of nestlings. In this study, we investigate the effect of reproductive effort on female survival in the dung beetle, Onthophagus taurus. By experimentally manipulating mating status and dung availability, we demonstrate that virgin females survive longer than mated females and that the survival of mated females was negatively associated with the number of brood masses produced. Using a novel manipulation of the mating system, we separated the effects of egg production and maternal care on female survival. Previously, we have shown that females provisioning with the assistance of a major male provide relatively less care than unassisted females. However, paternal assistance did not alter the number of brood masses produced and hence the amount of reproductive effort that was allocated to egg production. Therefore, our finding that female survival was increased when receiving paternal assistance provides, to our knowledge, the first definitive evidence that maternal care reduces female lifespan. These results are of major importance to theoretical models on the evolution of parental care.     

Effects of multiple mating and male eye span on female reproductive output in the stalk-eyed fly, Cyrtodiopsis dalmanni

Females of the stalk-eyed fly, Cyrtodiopsis dalmanni, mate repeatedly during their lifetime and exhibit mating preferencefor males with large eye span. How these mating decisions affectfemale fitness is not fully understood. In this study, we examinedthe effects of multiple mating and male eye span on short-termreproductive output in this species. Experiments that manipulatedthe number of copulations and partners a female received suggested that obtaining a sufficient sperm supply is an important benefitassociated with multiple mating. The average percentage offertile eggs laid by females increased as a function of matingfrequency and ranged from 40% for females mated once, to 80%for females mated continuously. In addition, a high proportionof copulations in this species appeared to be unsuccessful. One-third of all females mated once laid less than 10% fertileeggs. There was no significant difference in reproductive performancebetween females mated to multiple partners and females matedto a single partner. There was also no indication that femalesreceived any short-term reproductive benefits from mating withmales with large eye span. In fact, females mated to males with short eye span laid a higher percentage of fertile eggs thanfemales mated to large eye span males.     

Male house mice produce fewer offspring with lower viability and poorer performance when mated with females they do not prefer

We report experimental results consistent with the hypothesis that constraints on the expression of male mating preferences affect breeder fitness, offspring viability and performance. If constraints on the expression of mating preferences are common, tests of fitness variation associated with mate preferences must eliminate as many constraints on mate preferences as possible. We tested whether male mate preferences influenced breeder fitness, offspring performance and viability in typically polygynous house mice, Mus domesticus, from a feral source population. Our ‘free mate choice’ trials not only eliminated female preferences, male-male and female-female competition, but also our best guesses of the traits mediating choosers' preferences. Males mated with their preferred (P) females sired more litters than males mated with their nonpreferred (NP) females. Offspring viability was significantly lower when males' reproduced with females they did not prefer compared with females they did prefer. Adult sons of males that mated with their P females were socially dominant to sons of males that mated with their NP females. Adult offspring from P pairings built better nests than offspring from NP pairings. The slope of the survivorship curve for P offspring was significantly higher than for NP offspring. These results showed (1) males' mate preferences affected their fitness, (2) males that mated with females they preferred produced more litters than males that mated with females they did not prefer, and (3) their offspring were significantly more viable and performed significantly better on standardized performance tests. This is the first demonstration of fitness benefits of male choice behaviour in a mammal species with typical paternal investment. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Food availability and secondary sex ratio variation in wild and laboratory house mice (Mus musculus)

Female house mice deprived of food intermittently for 1 week before mating gave birth to fewer male young, but litters of females deprived of food for 2 weeks did not differ from control litters. Since mean weights of females did not differ between the two treatments, our results suggest that females were initially stressed by food deprivation, but recovered in the second week.     

Anomalous litters in hybrid mice and the retention of spermatozoa in the female tract.

Suspected superfetation was investigated in a Glasgow hybrid stock of mice. The male was removed either (i) a few days before parturition, or (ii) immediately after mating and on 23 and 25 occasions, respectively, a second litter was born. Members of the anomalous litters were inbred for 10 generations, but the incidence of supernumerary litters did not increase beyond 2-5%. The anterior part of over 500 reproductive tracts, at various stages of pregnancy and after parturition, were serially sectioned but a second set of embryos was not found. The second gestation was of normal length and superfetation was not therefore considered to be the cause of the anomalous litters. In two females, one non-pregnant and one pregnant, spermatozoa were found in the uterus and oviducts 8 days after mating and in distended uterine glands 15 days after mating respectively. It is concluded that the anomalous litters were derived from the fertilization of eggs ovulated at the post-partum oestrus by spermatozoa which had been retained in the female tract for at least 23 days.     

Male × female interaction for a pre-copulatory trait, but not a post-copulatory trait, among cosmopolitan populations of Drosophila melanogaster

Sexual coevolution occurs when changes in the phenotype of one sex select for changes in the other sex. We can identify the "footprint" of this coevolution by mating males and females from different populations and testing for a male-female genotype interaction for a trait associated with male (or female) performance. Here we mated male Drosophila melanogaster from five different continents with females from their own and different continents to test for a male-female interaction for mating speed, a pre-copulatory trait, and female reproductive investment, a post-copulatory trait. We found a strong male-female interaction for mating speed, consistent with previous studies using different populations, suggesting that the potential for sexual coevolution for this trait is present in this species. In contrast, we did not detect a male-female interaction for female reproductive investment. Although a male-female interaction for mating speed is compatible with the hypothesis of ongoing sexual coevolution, the nature of our experimental design is unable to exclude alternate explanations. Thus, the evolutionary mechanisms promoting male-female genotype interactions for pre-copulatory mating traits in D. melanogaster warrant further investigation.     

Short‐Term Nutritional Limitation Affects Mating Behaviour and Reproductive Output in Dwarf Spiders

Mating decisions can vary considerably depending on individual experience, mate availability and nutritional status. Here, we applied short‐term dietary restrictions to adult female spiders that were well fed during the juvenile stage in an effort to understand whether and how brief periods of food shortage can influence male and female mating decisions and mating behaviour. To assess whether responses vary between closely related species, we conducted the same experiment on the dwarf spiders Oedothorax retusus and O. apicatus. During courtship and mating, males of both species offer secretion to females from glandular tissue in their prosoma. Females were subject to food shortage over a period of 3 wks (‘low‐diet’ treatment, LD) or fed regularly (‘high‐diet’ treatment, HD). We compared courtship probability, mating probability/behaviour, and reproductive output between dietary groups and species. In both Oedothorax species, females in the LD treatment were less likely to mate and more aggressive towards males. Furthermore, LD females produced egg sacs that were significantly lighter than were those of the HD females. Effects of food deprivation on copulation duration, gustatory behaviour and oviposition latency differed between species. Our study shows that short periods of dietary restriction during the adult stage can strongly affect mating behaviour and reproductive output with differences between closely related species.     

Reproductive development of northern and southern strains of plum curculio (Coleoptera: Curculionidae)

Laboratory-reared southern and field-collected northern strains of plum curculio, Conotrachelles nenuphar (Herbst), were sampled to examine the relationship between degree-day (DD) accumulation and female reproductive development, as measured by mating status, oocyte size, and number of oocytes. The overall goal was to generate an objective degree-day model for predicting damage potential that could be applied to various host commodities rather than relying on separate biofix models for each crop. Adult beetles were dissected to measure mating status, maximum oocyte size, and number of oocytes. Southern strain beetles reared at 25 degrees C initiated mating 9 d after eclosion and did not require mating to induce oocyte development. By 20 d posteclosion, unmated females had significantly higher egg loads compared with mated females of the same age. Logistic regression analysis suggests that southern and northern strain beetles had a stable maximum oocyte length of 62 and 72 microm, respectively. Northern strain females mated after overwintering; with approximately 95% of the female population mated after 134 DD (base 10 degrees C), which is before fruit set in many host crops. Oocyte size was the only measured parameter of field reproductive progress that could be linked with confidence to degree-day accumulation. The other two parameters do not share an exclusive relationship with degree-days. Rapid assessment of field-caught female reproductive status could assist in determining the potential for plum curculio damage in high-value commodities and allow for more informed control decisions.     

Does long-term storage of spermatozoa occur in the adder (Vipera berus)?

In the adder ( Vipera berus) multiple inseminations during the spring mating season have been demonstrated, with fertilization taking place several weeks after mating activities have ceased. Subsequent sperm competition in the female reproductive tract can result in within-season mixed paternity. Prolonged sperm storage between mating seasons has been suggested as another mechanism of sperm competition in the adder. Competition between new and old spermatozoa would obstruct efforts to reveal reproductive strategies that correlate observed behaviour to paternity in natural populations. In the present study, controlled breeding experiments with adders were performed and DNA fingerprinting was used to determine paternity among all offspring of a total of 15 litters. The offspring of 11 large females, that had most probably also mated in a previous season, were sired exclusively by enclosure males. This result and earlier empirical data support the hypothesis that long-term sperm storage, over one or several reproductive cycles, does not occur in the adder.     

The male and female perspective in the link between male infant care and mating behaviour in Barbary macaques

Infant care from adult males is unexpected in species with high paternity uncertainty. Still, males of several polygynandrous primates engage in frequent affiliative interactions with infants. Two non‐exclusive hypotheses link male infant care to male mating strategies. The paternal investment hypothesis views infant care as a male strategy to maximize the survival of sired offspring, while the mating effort hypothesis predicts that females reward males who cared for their infant by preferably mating with them. Both hypotheses predict a positive relationship between infant care and matings with a particular female. However, the paternal investment hypothesis predicts that increased matings come before infant care whereas the mating effort hypothesis predicts that infant care precedes an increase in matings. Both hypotheses are usually tested from the perspective of the proportion of matings and care that individual females engage in and receive, rather than from the perspective of the care and mating behaviour of individual males. We tested the relationships between care and mating from both female and male perspectives in Barbary macaques. Mating predicted subsequent care and care predicted subsequent mating when viewed from the male but not the female perspective. Males mainly cared for infants of their main mating partners, but infants were not mainly cared for by their likely father. Males mated more with the mothers of their favourite infants, but females did not mate more with the main caretakers of their infants. We suggest that females do not choose their mating partners based on previous infant care, increasing paternity confusion. Males might try to increase paternal investment by distributing the care according to their own instead of female mating history. Further, males pursue females for mating opportunities based on previous care.     

Mating modifies female life history in a haplodiploid spider mite

Mating usually modifies females' resource allocation pattern, often as a result of conflicts between male and female partners. Can such a switch occur even in the absence of sexual conflicts? We addressed this issue in the haplodiploid spider mite Tetranychus urticae, whose biology and population structure considerably reduce conflicts between males and females over reproductive decisions. Comparing virgin and mated females, we tested the hypothesis that mated females modify their allocation pattern so as to maximize their probability of producing daughters. Mated females produced fewer but larger eggs, resulting in an overall similar reproductive effort but an increased probability of producing daughters, since in this species larger eggs are more likely to be fertilized and thus to become female. Moreover, mated females concentrated their reproduction early in life. Again, this might be a way to produce more daughters, since sperm is more abundant early in life. For virgins, spreading reproductive investment might be a way to save resources to extend life span, thus increasing their probability of encountering a sexual partner. Females with multiple opportunities for mating produced fewer eggs and a less female-biased sex ratio than once-mated females, raising the question of why multiple mating often occurs in this species.     

Factors influencing paternity success in Antechinus agilis: last‐male sperm precedence,timing of mating and genetic compatibility

We describe the patterns of paternity success from laboratory mating experiments conducted in Antechinus agilis, a small size dimorphic carnivorous marsupial (males are larger than females). A previous study found last‐male sperm precedence in this species, but they were unable to sample complete litters, and did not take male size and relatedness into account. We tested whether last‐male sperm precedence regardless of male size still holds for complete litters. We explored the relationship between male mating order, male size, timing of mating and relatedness on paternity success. Females were mated with two males of different size with either the large or the small male first, with 1 day rest between the matings. Matings continued for 6 h. In these controlled conditions male size did not have a strong effect on paternity success, but mating order did. Males mating second sired 69.5% of the offspring. Within first mated males, males that mated closer to ovulation sired more offspring. To a lesser degree, variation appeared also to be caused by differences in genetic compatibility of the female and the male, where high levels of allele‐sharing resulted in lower paternity success.     

Mating experience weakens starvation tolerance in the seed bug Togo hemipterus (Heteroptera: Lygaeidae)

Organisms are exposed to various stresses caused by environmental fluctuations. One of the most common stresses is the shortage of food. Individuals of many species must survive periods of starvation. There appears to be a trade‐off between reproduction and survival. When residual reproductive value declines for an individual, life‐history theory predicts an increase in current reproductive investment. Current reproductive investment differs between virgin and mated individuals. It is likely that mating experience influences starvation tolerance. However, few studies have investigated sex differences in the effect of mating experience on starvation tolerance or clarified the causes of reductions in starvation tolerance in both sexes. In the present study, these questions are investigated using the seed bug Togo hemipterus (Heteroptera: Lygaeidae).The results of the present study demonstrate that mating is costly for both sexes. Mated males show very short survival times and a daily reduction in weight, and daily energy expenditures are significantly greater in mated males than in virgin males. It is possible that starvation increases the mating effort of males, such as behavioural activities and the amount of time spent searching for females. A trade‐off between survival duration and lifetime fecundity is found in virgin females. However, there is no trade‐off in mated females, which have very short survival times. Whether male seminal substances contribute to the short survival times of mated females is considered. This is the first report demonstrating the influence of sex and mating experience on starvation tolerance. Sex‐specific causes for reductions in starvation tolerance are discussed.     

Genetic polyandry and sexual conflict in the sandbar shark, Carcharhinus plumbeus, in the western North Atlantic and Gulf of Mexico

To investigate patterns of polyandry in the sandbar shark (Carcharhinus plumbeus), 20 pregnant females were sampled from the western North Atlantic and Gulf of Mexico. Five species-specific microsatellite markers were used to genotype each shark and its litter. Of 20 litters, 17 (85%) were shown to have multiple sires. In multiply sired litters, the estimated minimum number of sires ranged from two to five with an average of 2.3 males per litter. Regression analysis did not demonstrate a significant relationship between female reproductive success and female body size or sire number and female body size. There was a high incidence of reproductive skew noted in litters, and two groups of males with significantly different mean reproductive success were observed. Analyses using Bateman's principles suggest that there is less direct benefit for females that acquire multiple mates than for males who bias paternity within litters. In light of past morphological and behavioural studies, these data suggest that patterns of polyandry in elasmobranchs may be determined by coercive mating, and that breeding behaviour has likely evolved in the context of sexual conflict.     

Aspects of mating, reproduction, and co-occurrence in three freshwater calanoid copepods

SUMMARY. 1. We examined the seasonal distributions and mating behaviour of Epischura lacustris, Diaptomus minutus and Diaptomus oregonensis to evaluate several proposed mechanisms for reproductive isolation. There was no divergence in onset of maturity or timing of breeding periods between sympatric diaptomid populations; size displacement between co-occurring diaptomid species did not result in concomitant reduction in mating frequency between heterospecific pairs in the laboratory.
2. Divergence in mating behaviour was supported by observations that, in conspecific mating experiments, males of both diaptomid species discriminated between females bearing ripened ovaries (gravid) and those that did not (non-gravid), and that, in heterospecific trials, males either mated indiscriminantly with all females, or engaged in mating very infrequently.
3. In mating experiments with Epischura. males did not discriminate between gravid and non-gravid females, but mated exclusively with virgins of a specific relative size. Divergence in timing of breeding seasons between Epischura and the two diaptomid species suggests that even if mating between genera is possible, it does not occur often in nature.
4. We discuss the adaptive significance of different reproductive strategies of these three copepods and speculate on mechanisms that allow for coexistence of the closely related taxa in nature.