Male Mating Frequency Research Articles

The Sex Ratio Indicates the Conclusion and Onset of Population Cycles in the Beet Webworm Loxostege sticticalis L. (Lepidoptera: Pyralidae).

Beet webworms, Loxostege sticticalis L. (Lepidoptera: Pyralidae), are one of the most destructive pest insects in northern China, and their populations outbreak periodically. Developing an indicator that defines the ending and beginning of the occurrence period cycle is urgent for the population forecast and theoretical study. The sex ratio can be a primary pathway through which species regulate population size. We measured the maximum mating potential of both females and males and the population net reproductive rate under different sex ratios (e.g., 3:1, 2:1, 1:1, 1:2, 1:3). The maximum mating frequency of males was 2.91 times that of females. The progeny contribution per mating decreased with increased mating times in males. The variation in population net reproductive rate affected by the sex ratio fits the parabolic curve analysis and peaked at 1.82 for females vs. males. Our results illustrate the quantitative connection phenomenon shown by the historical data: population outbreaks occur at a sex ratio of two or more and collapse at a sex rate lower than one. Simultaneously, the sex ratio may be utilized as a definite indicator for the beginning and end of the future occurrence cycle in the beet webworm.

Feeding on methoprene increases male accessory gland size and body protein in the Mexican fruit fly

AbstractMethoprene, a juvenile hormone analog, accelerates male sexual maturation in some pest species controlled through the Sterile Insect Technique (SIT). The SIT consists of the mass‐rearing, irradiation and release of insects into affected areas, where sterile males mate with wild females and render them infertile. Sterile males are held for 6 days in confinement before release, and they are often released before attaining sexual maturity. The use of methoprene during this time has been shown to increase male mating frequency. However, very little is known on the effects of methoprene on the reproductive physiology of tephritid pests, including male accessory gland size, whole body protein content, sperm transfer and female remating receptivity. Here we found that sterile Anastrepha ludens males fed methoprene with only a 1:24 protein to sugar diet had greater male mating frequency and bigger male accessory glands compared to males deprived of methoprene. Furthermore, positive effects of methoprene inclusion in the diet were found on the amount of sperm stored by females, and body protein content but only when males fed sugar only. Inclusion of methoprene in the diet did not affect remating propensity of wild females having mated with sterile males. Females mating with young 5‐day‐old males stored fewer sperm than females mating with older males regardless of diet. The use of methoprene as a pre‐release supplement can positively impact early sexual maturation, energy reserves and male reproductive organs of A. ludens males, thus supporting its use in SIT programmes controlling this pest.

Male accessory gland depletion in a tephritid fly affects female fecundity independently of sperm depletion

Production of female gametes is costly; however, there is now wide evidence across different taxa that male ejaculates are also limiting. Thus, multiply mated males may need to partition their ejaculate across successive matings. While more attention has been payed to whether female mating with previously mated males could be sperm limited, there have been fewer studies on depletion of other substances transferred in the male ejaculate such as accessory gland products. Here, we assessed whether male mating frequency affected mating success, copula duration, mating latency, and sperm stored by females. In addition, we measured male testes and accessory gland size across consecutive matings and evaluated the effect of male multiple mating on female fecundity, fertility, and remating propensity in the South American fruit fly, Anastrepha fraterculus. We show that males have the capacity to modulate ejaculate expenditure, and although sperm storage dramatically decreased after the first mating, this had no effect on female reproductive parameters. However, males mating with five consecutive females had smaller accessory glands. Females mated with males who had previously mated five times failed to lay any eggs. This lower propensity to lay eggs could suggest that males become depleted of products synthetized in the accessory glands, including peptides that have an effect on oogenesis and/or egg laying. We discuss our results in terms of cost of production of male accessory gland products and the impact on female fitness according to male mating history. During insect copulation, males transfer to females’ seminal fluids composed of sperm and accessory gland (AG) products. Sperm depletion over male consecutive matings and its impact on female reproductive success have been explored in the past years; however, AG depletion and its effects on female physiology and behavior remain practically unexplored. We show for the fruit fly, Anastrepha fraterculus, that male multiple matings have a dramatic impact on female fecundity and fertility after males achieve five copulations, and this effect seems mediated by depletion and lack of replenishment of products synthetized in the AG, inferred through their size reduction. In contrast, while sperm transfer was markedly higher for virgin than for multiply mated males, this did not affect female fecundity or fertility, showing that the dynamics of seminal fluid components can differ.

Mitonuclear mismatch alters performance and reproductive success in naturally introgressed populations of a montane leaf beetle.

Coordination between nuclear and mitochondrial genomes is critical to metabolic processes underlying animals' ability to adapt to local environments, yet consequences of mitonuclear interactions have rarely been investigated in populations where individuals with divergent mitochondrial and nuclear genomes naturally interbreed. Genetic variation in the leaf beetle Chrysomela aeneicollis was assessed along a latitudinal thermal gradient in California's Sierra Nevada. Variation at mitochondrial cytochrome oxidase II (COII) and the nuclear gene phosphoglucose isomerase (PGI) shows concordance and was significantly greater along a 65 km transect than 10 other loci. STRUCTURE analyses using neutral loci identified a southern and northern subpopulation, which interbreed in the central drainage Bishop Creek. COII and PGI were used as indicators of mitochondrial and nuclear genetic variation in field and laboratory experiments conducted on beetles from this admixed population. Fecundity, larval development rate, running speed and male mating frequency were higher for beetles with geographically "matched" than "mismatched" mitonuclear genotypes. Effects of mitonuclear mismatch were largest for individuals with northern nuclear genotypes possessing southern mitochondria and were most pronounced after heat treatment or at high elevation. These findings suggest that mitonuclear incompatibility diminishes performance and reproductive success in nature, effects that could intensify at environmental extremes.

The mating strategy and reproductive performance of Agriphila aeneociliella (Lepidoptera: Crambidae), a new insect pest of wheat in China

Abstract The Eastern Grass‐veneer Agriphila aeneociliella (Eversmann) (Lepidoptera: Crambidae) is a serious stem‐feeding pest of wheat crops that has become established in China in recent years. A better understanding of the mating strategy and reproductive performance of A. aeneociliella could improve integrated pest management programmes against this newly established species by disturbing its behaviour and reducing its reproduction potential. Based on ethological and reproductive biological approaches, the mating and reproductive performances of A. aeneociliella were investigated. Unlike the common nocturnal lepidopterans, the mating rhythm of A. aeneociliella moths showed a marked diurnal pattern. The female courtship rhythm and the mating rhythm reached peaks within the first 2 h after the onset of photocycle. The mating success rate of monogamous pairs was 55.6%, whereas the male‐biased sex ratio (2♂:1♀) increased the mating rate (72.2%) and the female‐biased ratio (1♂:3♀) led to the lowest mating rate (27.8%). Both females and males were able to mate twice. The duration of copulation decreased substantially with male mating frequency, whereas, when a previously mated female was paired with a virgin male, fecundity significantly increased. Monogamous couples who mated only once in their lives have the highest hatchability (97.13 ± 0.49%).

Maintenance of Fertility in the Face of Meiotic Drive.

Selfish genetic elements that gain a transmission advantage through the destruction of sperm have grave implications for drive male fertility. In the X-linked meiotic drive system (SR) of a stalk-eyed fly, we found that SR males have greatly enlarged testes and maintain high fertility despite the destruction of half of their sperm, even when challenged with fertilizing large numbers of females. Conversely, we observed reduced allocation of resources to the accessory glands that probably explains the lower mating frequency of SR males. Body size and eye span were also reduced, which are likely to impair viability and precopulatory success. We discuss the potential evolutionary causes of these differences between drive and standard males.

Estimation of multiple male mating frequency using paternity skew: An example from a grey-sided vole (Myodes rufocanus) population.

Multiple male mating (MMM) causes sperm competition, which may play an important role in the evolution of reproductive traits. The frequency of multiple paternity (MP), where multiple males sire offspring within a single litter, has been used as an index of MMM frequency. However, MP frequency is necessarily lower than MMM frequency. The magnitude of the difference between MMM and MP frequency depends on litter size (LS) and fertilization probability skew (FPS), and this difference may be meaningfully large in animals with small LSs. In this study, we propose a method to estimate MMM frequency using an individual-based model with three variables (MP frequency, LS and FPS). We incorporated observed paternity skew data to infer a possible range of FPS that cannot be measured in free-living populations and tested the validity of our method using a data set from a grey-sided vole (Myodes rufocanus) population and from hypothetical populations. MP was found in 50 out of 215 litters (23.3%) in the grey-sided vole population, while MMM frequency was estimated in 67 of 215 litters (31.2%), with a certainty range of 59-88 (27.4%-40.9%). The point estimation of MMM frequency was realized, and the certainty range was limited within the practical range. The use of observed paternity skew was very effective at narrowing the certainty range of the estimate. Our method could contribute to a deeper understanding of the ecology of MMM in free-living populations.

Effect of gut bacteria on fitness of the Chinese citrus fly, Bactrocera minax (Diptera: Tephritidae)

A likely symbiotic association between tephritid fruit flies and gut bacteria has been recognized since the beginning of the last century. However, direct evidence for a link between gut bacteria and fruit fly fitness is still limited or absent for many species. Similar to other tephritids, the gut of Bactrocera minax (Enderlein) (Diptera: Tephritidae) is known to contain bacteria throughout the life stage, but what, if any, impact these bacteria have on B. minax fitness is entirely unknown. In order to elucidate the effects of bacteria on the fitness of B. minax, resident bacteria were isolated from the adult gut using culture-dependent techniques. Adult fly diets were subsequently supplemented with three bacterial isolates (Klebsiella pneumonia, Citrobacter braakii and Pantoea dispersa), or bacteria were removed from flies by antibiotics treatment: untreated adults provided a control. Adult fitness parameters (male and female longevity, female fecundity, male copulation number) were measured for the two treatments and one control group. Results were complex depending on the fitness parameter measured and the bacterial species. Compared to the controls, antibiotic treated B. minax had significantly decreased fecundity, but male and female longevity was increased. When flies were fed diets supplemented with any of the three bacterial isolates, female fecundity was significantly enhanced. However, only Citrobacter braakii significantly increased male mating frequency than control males. The results show that gut bacteria directly influence fitness of B. minax, but impacts are dependent on the bacterial species and the fitness parameters measured.

Reproductive behavior of the masson pine caterpillar, Dendrolimus punctatus (Lepidoptera: Lasiocampidae) under laboratory conditions

The pine caterpillar, Dendrolimus punctatus Walker (Lepidoptera: Lasiocampidae), is one of the most serious defoliators of pine trees (Pinus spp.) in China. Despite this, little is known with regard to the reproductive behavior of this insect. In the present study, we investigated the circadian rhythm of adult eclosion, mating and oviposition under laboratory conditions. The age at which moths mate and the frequency and duration of mating bouts were recorded. Eclosion and mating behavior were limited to nocturnal hours. Male and female eclosion peaked between 3 and 4 h, and between 4.5 and 5.5 h after the initiation of scotophase, respectively. Mating behavior peaked between 10 and 11.5 h after the initiation of scotophase. Most ovipositions occurred during the scotophase, displaying one distinct peak between 3 and 3.5 h after the initiation of scotophase. More than 70 % of matings occurred on the first scotophase after adult eclosion and the percentage of successful matings declined dramatically with moth age, indicating age was an important factor in the mating success of this species. If males or females paired with newly ecloced virgin partners after each successful mating, 57.6 % of males and 24.2 % of females mated more than once, mating an average of 2.0 ± 0.2 and 1.3 ± 0.1 times, respectively, suggesting males are generally polygynous, while females are monandrous. The copulation duration of this moth lasted on average 16.6 ± 0.1 h and was not influenced by moth age and female mating frequency, but was negatively influenced by male mating frequency. These data provide basic information to further study the mating system of D. punctatus, and could lead to the development of behavior-based pest control strategies of this species.

Temporal dynamics of intersexual conflict and the effect of male quality on female fecundity in the marine isopod Cleantiella isopus

Crustacean males grasp and/or guard females before copulation to ensure mating, but females typically resist males during pair formation. The benefit of resistance for females might allow (1) females to optimize mate quality, or (2) to avoid costs incurred during guarding. However, it has not been fully investigated which benefits actually improve female fitness. Here we investigated female resistance, temporal dynamics of intersexual conflict during reproduction, and the effect of male size and male mating frequency on female fecundity in the marine isopod,Cleantiella isopusto examine the relative importance of the two mechanisms mentioned before. Females resisted even after they had become receptive. Females which mated with small males showed lower fecundity than the ones with large males, and small males were frequently unable to form pairs. These results suggest that female resistance ofC. isopusagainst males can function as a way to optimize mate quality.

Old male sex: large ejaculate, many sperm, but few offspring

Reproduction induces non-trivial costs, such that both males and females should choose their mates carefully and invest their resources prudently. Male performance and thus their investment into ejaculates are often predicted to decrease with age and mating frequency, which may in turn negatively affect female fitness and thus feedback on the attractiveness of old males. Such reproductive senescence may be mediated by changes in the males’ oxidative status. Here, we investigated the effects of male mating frequency and age on male reproduction and oxidative status, and the respective consequences for female reproduction. We used the tropical butterfly Bicyclus anynana, in which counterintuitively older males have a higher mating success than younger ones. In once-mated males, spermatophore mass and sperm numbers strongly increased with age, while antioxidant defences and oxidative damage declined with age. In repeatedly mated males, spermatophore mass and sperm number showed little variation being similar to young once-mated males, while antioxidant defences increased and oxidative damage decreased with mating frequency. Female reproductive success was highest when mating with young once-mated males, although these produced small spermatophores with low sperm numbers. Our findings suggest that in B. anynana, (1) ejaculate size and sperm number are not reliable proxies of male quality, (2) ejaculate quality diminishes with age and mating number, and that (3) old male mating advantage likely results from sexual conflict owing negative effects on female fitness.

Last male sperm precedence in a polygamous squid

Differential sperm usage from consecutive matings, or sperm precedence, is vital in determining male reproductive success and the outcome of sperm competition for many organisms. Sperm precedence also has significant consequences for mating system dynamics, including both male and female adaptations for increasing reproductive success and avoiding the costs of mating. Despite sexual selection being a strong driver of reproductive behaviour and morphology in cephalopods, surprisingly few studies have investigated sperm dynamics in this group. To redress this gap, we experimentally quantified sperm precedence patterns in the dumpling squid, Euprymna tasmanica, controlling for recent male mating history (first vs. second mating), mating position, and mating frequency. We found that the last male to mate gains an advantage in this system, with the second mating male siring up to 75% of offspring at the beginning of the laying period. The proportion of offspring attributable to the second mating male decreases to 54% by the end of the laying period, potentially as a result of changes in the velocity or number of sperm released from spermatangia over time. There is also significant variation among females in patterns of sperm precedence. This variation was not associated with whether it was the male's first or second mating, male mass, the duration of copulation or the number of pumps (sperm removal behaviour) by the second male. If widespread in cephalopods, last male sperm precedence could help to explain the evolution of mate guarding (or long copulation duration) and sperm removal behaviour in this group.

Attractiveness and competitiveness of irradiated light brown apple moths

AbstractThe sterile insect technique (SIT) potentially provides a socially acceptable approach for insect eradication of new pest incursions. The light brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), was discovered in Berkeley (CA, USA) in 2006, leading to an incursion response that included this technology. In this study, we assessed factors affecting mating success from a bisex release of irradiated moths: effects of radiation dose on male multiple mating, male flight competition, female sex pheromone titre and attractiveness of irradiated females to males, and identification of successful mating in vineyards of either irradiated or wild males (identified by isotope analysis of spermatophores from sentinel females). There was a significant negative relationship between male radiation dose and mating frequency. In head‐to‐head flights of irradiated males against non‐irradiated males to a pheromone lure in a wind tunnel, irradiated males reached the lure first only 31% of the time. With increasing radiation dose, the production of the major sex pheromone component in females, (E)‐11‐tetradecenyl acetate, dropped, from 0.7 ± 0.1 ng per female in non‐irradiated females to 0.2 ± 0.07 ng per female when irradiated at 300 Gy. Male catch was reduced to 11% of control females in traps containing females irradiated at 300 Gy. Isotope analysis of spermatophores found in the bursa copulatrix of females indicated that mating success of irradiated males inside the live (entry‐only) traps containing virgin females was lower (13.1 ± 3.3%) than suggested by male catch (21.2 ± 3.8%) in pheromone traps, the current standard for assessing field competitiveness. Impacts of irradiation on male and female moth fitness should be taken into account to improve estimates of irradiated to wild male E. postvittana overflooding ratios needed for population suppression.

蝇蛹金小蜂的交配行为及雄蜂交配次数对雌蜂繁殖的影响

多数昆虫能够进行多次交配,随寄生蜂雄蜂交配次数的增加,雄蜂体内精子减少,雌蜂获得的精子数量减少,产下更多的单倍体卵,发育为雄性后代;一些单寄生性的寄生蜂雌蜂一生仅能够交配1次。描述了蝇蛹金小蜂雌雄蜂的交配行为,探讨了雄蜂交配次数对雌蜂后代产量等的影响以及雌蜂的可交配次数。结果表明,交配过程包括求偶、交尾前期、交尾和交尾后期;雄蜂已交配的次数并不能够显著影响其配偶的寿命、产卵期和后代总数量,但显著影响到其配偶的雌、雄后代数量和性比。随雄蜂交配次数的增加,与之交配的雌蜂的后代雄性百分比显著增大,雌蜂在产卵期内更早地出现较多雄性后代,体内精子不足的现象更加明显。无论已交配的蝇蛹金小蜂雌蜂在产卵期中是否出现精子不足,均不能再次完成交配。;Most insects can mate multiple times. With the increasing of male mating frequency, male parasitoid wasps would have less sperm, and the female partners would gain less sperm during copulation, which will make them lay more unfertilized eggs, developing into male offspring. Some solitary female parasitoid wasps can only mate once in the life span. In this article, the mating behavior of the solitary endoparasitoid, <em>Pachycrepoideus vindemmiae</em> Rondani, was described, with the pupae of houseflies as the hosts, and the effects of male mating frequency on the production of the female partners and the possible mating times of the mated females were studied. The results showed that the mating behavior of <em>P. vindemmiae</em> included courtship, precopulatory, copulation, and postcopulatory, which lasts (41.21±83.16) s, (26.05±17.99) s, (2.62±0.62) s, and (30.43±11.44) s, respectively. When mated with males for the 1^st, 3^rd, 6^th, 9^th, 12^th, and 15^th times, the longevity of the females was (11.18±7.17) d, (10.82±8.51) d, (9.09±5.74) d, (9.36±4.74) d, (9.64±3.47) d, and (13.45±7.03) d, respectively, and the oviposition duration was (9.73±7.52) d, (9.82±8.51) d, (7.55±5.20) d, (8.18±4.71) d, (8.55±3.50) d, and (11.64±7.50) d, respectively. The total progeny number was (57.00±39.15), (50.18±35.52), (44.18±24.62), (42.55±15.69), (47.27±18.23), and (62.09±37.55), respectively, and the male proportion was (0.21±0.19), (0.17±0.06), (0.27±0.22), (0.43±0.31), (0.45±0.30), and (0.63±0.34), respectively. The mating frequency of males did not significantly affected longevity, oviposition duration and total progeny number of the female partners, but significantly affected the production of female and male progeny and offspring sex ratio, respectively. With the increasing of male mating times and with the increasing of female oviposition duration, daily female offspring number per foundress decreased, but male offspring number increased. When males mated for the 1^st, 3^rd, 6^th, 9^th, 12^th, and 15^th times, females laid offspring with male proportions higher than 50% on the 8^th, 17^th, 11^th, 6^th, 5^th, 2^nd day, respectively. The interaction of female ages and mating frequency affected offspring sex ratio significantly. After mated with the males which had mated multiple times, females laid more male offspring earlier, which suggests the sperm limitation in females was more obviously when they had mated with multiply mated males. Mated females could not finish mating again neither just after mating nor after they had laid eggs for 8 days, which suggests females might mate only once in their life span, no matter whether they lack sperm or not.

Male mating behaviour in relation to female sexual swellings, socio-sexual behaviour and hormonal changes in wild Barbary macaques

In many cercopithecine primates females display probabilistic cues of fertility to indicate the periovulatory period to males. These cues may include female behaviour, acoustic signals, and morphological signs such as the anogenital swelling. However, the extent to which males can utilise this information varies between species. We describe male sexual behaviour in relation to changes in anogenital swelling size, timing of ovulation and female socio-sexual behaviour in wild Barbary macaques (Macaca sylvanus). We further compare male sexual behaviour during conception and post-conception cycles to evaluate if males differentiate between these qualitatively different cycle types. Our results show that during conception cycles male mating behaviour was concentrated around the fertile phase implying that males inferred information from more than swelling size alone. Male mating frequency increased in line with female socio-sexual behaviour, namely female presenting and the frequency of copulations with copulation calls. Most strikingly our results show that males invested equally in mating during fertile and non-fertile, i.e. post-conception, maximum swelling phases. Whether post-conception swellings were merely a result of changes in hormone concentrations during pregnancy or part of a female reproductive strategy remains elusive. In sum, this study adds to the body of research on the evolution of female sexual signals and how males may infer information from these cues.

Variation in adult sex ratio alters the association between courtship, mating frequency and paternity in the lek‐forming fruitfly Ceratitis capitata

The intensity with which males deliver courtship and the frequency with which they mate are key components of male reproductive success. However, we expect the strength of the relationship between these traits and a male's overall paternity to be strongly context dependent, for example to be altered significantly by the extent of post-mating competition. We tested this prediction in a lekking insect, Ceratitis capitata (medfly). We examined the effect of manipulating the sex ratio from male- to female-biased (high and low male competition, respectively) on courtship behaviour, mating frequency and paternity of focal males. Under high male competition, focal males delivered significantly more courtship but gained lower paternity than under lower competition. Paternity was positively associated with mating frequency and small residual testes size. However, the association between mating frequency and paternity was significantly stronger under low competition. We conclude that manipulation of sex ratio significantly altered the predictors of mating success and paternity. The relationship between pre- and post-mating success is therefore plastic and alters according to the prevailing level of competition. The results highlight the importance of post-copulatory processes in lekking species and illuminate selection pressures placed on insects such as medflies that are mass reared for pest control.

Plausible causes for sperm-store variations in the coconut crab Birgus latro under large male‑selective harvesting

In populations subjected to size-selective harvesting of large males, remaining males are small and participate in more matings than in pristine populations. The reproductive rate of such harvested populations can be restricted due to sperm limitation, because the numbers of sperm passed to females decrease with decreasing male size and increasing male mating frequency. Japa - nese populations of the coconut crab Birgus latro are typical examples of populations that are subject to selective harvesting of large males. Reproductive output of the population may have declined via sperm limitation. However, there is no evidence that males exhaust sperm reserves through succes- sive matings, and little is known about the factors causing variations in the number of sperm retained by females in the harvested population. Using field investigations and laboratory experiments, I examined (1) whether males exhaust sperm reserves and (2) what factors cause variations in the number of sperm retained by females. About half of the males had exhausted sperm reserves by the end of the mating season. These males were found to be incapable of further mating or of ejaculating larger numbers of sperm, which was inferred from laboratory experiments. The size of individuals of both sexes participating in mating decreased as the mating season progressed, and males did not adjust ejaculate size in response to female size. Thus, variations in the number of sperm retained by females may have mainly been due to a decline in the male ability to ejaculate large numbers of sperm, due both to increased male mating frequency and decreased male size.

Dominance status and carcass availability affect the outcome of sperm competition in burying beetles

Intense intrasexual competition between males often results in the establishment of a dominance hierarchy, promoting differential access to females. Dominant males are expected to evolve more prudent sperm allocation strategies, whereas subordinate males are expected to counteract their mating disadvantage by increasing their sperm allocation. Burying beetles, insects that breed on small vertebrate carcasses, offer an ideal model for testing these predictions because aggressive interactions between males typically result in one dominant male that monopolizes access to the female, relegating subordinates to sneak matings. Males that have not found a carcass use pheromones to attract females and only obtain a small number of matings per day. We measured the mating frequency of males competing on a carcass and confirmed that dominant males mate significantly more often than subordinates. We then examined the paternity of competing males, with a 5:1 mating advantage for the dominant male, to determine whether relative mating frequency is sufficient to explain the severe reproductive skew in polyandrous broods in the field. When competing on a carcass, dominant males did not sire significantly more offspring than subordinates. However, when males mated without a carcass and did not interact, significantly more offspring were sired by the dominant male, but even here, the subordinate male’s paternity was greater than his share of matings. Our results show that when males compete on a carcass, dominant males have a clear mating advantage, whereas subordinates appear to transfer greater numbers of sperm per mating to compensate for their limited mating opportunities. Key words: burying beetles, dominance, intrasexual competition, Nicrophorus vespilloides, paternity, sperm competition. [Behav Ecol]

Male remating and female fitness in the wolf spider Pardosa astrigera: the role of male mating history

Although the effects of male mating history on female reproductive output and longevity have been studied in insects, few such studies have been carried out in spiders. In a mating system in which females are monandrous while males are polygynous, females may incur the risk by mating with successful males that have experienced consecutive matings and suffer from the possible depletion of sperm and/or associated ejaculates. Here, we examine the effects of male mating history on male courtship and copulation duration, female reproductive fitness, and female adult longevity of the wolf spider, Pardosa astrigera. Results indicated that male mating frequency had little effect on their subsequent copulation success, and of 35 males tested, about half of the males were able to copulate with five virgin females successively at an interval of 24 h. Male mating history had little effect on their courtship duration. However, male mating history significantly affected male copulation duration, female adult longevity, and reproductive output. Males that mated more frequently copulated longer and more likely failed to cause their mates to produce a clutch, although there was no significant difference in the number of eggs laid and the number of eggs hatched regardless of the first clutch or the second one. Multiple mating of male P. astrigera resulted in significant reduction in female adult longevity. Our results indicate that monandrous females mating with multiple-mated males may incur substantial fitness costs.

Sperm limitation: possible impacts of large male-selective harvesting on reproduction of the coconut crab Birgus latro

For many biological resources, larger males are more likely to be harvested than smaller ones. In such harvested populations, the remaining males are relatively small and participate in more matings than in pristine populations. Because the number of sperm passed to females generally decreases with decreasing male body size and increasing male mating frequency, the reproductive success of females in populations subjected to such harvesting patterns can be restricted due to sperm limitation. The Japanese population of the coconut crab Birgus latro is typically subject to large male-selective harvesting, which may be one of the causes of the presently observed B. latro population decline. To examine the impact of harvesting on coconut crab populations, the effects of male size and mating frequency on male reproductive potential (number of ejaculated sperm and fer- tilization rate), sperm recovery rate, and the number of sperm received by females in a harvested population were investigated. Larger males provided females with larger numbers of sperm and achieved higher fertilization rates. Although the number of ejaculated sperm decreased with increas- ing mating frequency regardless of male size, larger males always passed more sperm to successive mates than smaller ones. The number of used sperm did not increase even after 30 d, suggesting a low sperm recovery rate. More than half of the females collected after the beginning of the reproduc- tive season had very low numbers of sperm. These results suggest that the reproductive rate of the coconut crab has declined due to females suffering from sperm limitation.