Intrasexual Competition and Mating Behavior in <Emphasis Type="Italic">Ptomascopus morio</Emphasis> (Coleoptera: Silphidae Nicrophorinae)

In nicrophorine beetles, genus Nicrophorus care their larva using small vertebrate carrion, whereas genus Ptomaucopusreproduce with small vertebrate carrion but show no parental care. Aggression and sexual behavior were examined in Ptomascopus morio and Nicrophorus quadripunctatus. Nicrophorus quadripunctatus had intense female–female as well as male–male contests. In Ptomascopus morio, by contrast, female–female aggression was rarely observed. Male–male aggression (pushing, biting, male–male mounting) in Ptomascopus morio was observed when a resource for breeding was present, whether or not a female was present. The lack of female–female aggression, and male–male aggression when resources but not females are present, suggest that the mating system of Ptomascopus morio is resource defense polygyny. Large males of Ptomascopus morio were also found to exhibit mate choice, preferring large females over small females.     

Last–male sperm precedence in the bushcricket Poecilimon veluchianus (Orthoptera, Tettigonioidea) demonstrated by DNA fingerprinting

Males of the bushcricket Poecilimon veluchianus pass a large spermatophore to the female during mating. The spermatophore is eaten by the female after copulation. Because females mate with several males during their reproductive life, the competition between spermatozoa of different males affects a male's reproductive success. In order to determine the outcome of sperm competition, the paternity of the progeny of double–mated females was established by DNA fingerprinting with the oligonucleotide (GATA)₄. Typical P. veluchianus DNA fingerprints consisted of 15 scoreable fragments per individual. The proportion of bands shared between presumably unrelated bushcrickets was 17%. After the second copulation the second mating male clearly predominated at fertilization. The mean proportion of eggs fertilized by the second male was 90.1%. There was no significant relationship between the level of sperm precedence and the time of ovipositions after the second mating. If female P. veluchianus increase the fitness of their offspring by the incorporation of spermatophore–derived substances in developing eggs, there is little chance for the feeding male to fertilize eggs containing his nutrients, because of the very short mating intervals of females and the observed high level of last–male sperm precedence in this species. Under such conditions the last mating male would fertilize many eggs containing nutrients from a prior male. Because nuptial gifts, like the tettigoniid spermatophore, function only as paternal investment if the donating male's progeny benefit from the gift, a paternal investment function of the P. veluchianus spermatophore seems to be unlikely.     

Paternity analyses in wild‐caught and laboratory‐reared Caribbean cricket females reveal the influence of mating environment on post‐copulatory sexual selection

Polyandry is ubiquitous in insects and provides the conditions necessary for male‐ and female‐driven forms of post‐copulatory sexual selection to arise. Populations of Amphiacusta sanctaecrucis exhibit significant divergence in portions of the male genitalia that are inserted directly into the female reproductive tract, suggesting that males may exercise some post‐copulatory control over fertilization success. We examine the potential for male–male and male–female post‐copulatory interactions to influence paternity in wild‐caught females of A. sanctaecrucis and contrast our findings with those obtained from females reared in a high‐density laboratory environment. We find that female A. sanctaecrucis exercise control by mating multiple times (females mount males), but that male–male post‐copulatory interactions may influence paternity success. Moreover, post‐copulatory interactions that affect reproductive success of males are not independent of mating environment: clutches of wild‐caught females exhibit higher sire diversity and lower paternity skew than clutches of laboratory‐reared females. There was no strong evidence for last male precedence in either case. Most attempts at disentangling the contributions of male–male and male–female interactions towards post‐copulatory sexual selection have been undertaken in a laboratory setting and may not capture the full context in which they take place – such as the relationship between premating and post‐mating interactions. Our results reinforce the importance of designing studies that can capture the multifaceted nature of sexual selection for elucidating the role of post‐copulatory sexual selection in driving the evolution of male and female reproductive traits, especially when different components (e.g. precopulatory and post‐copulatory interactions) do not exert independent effects on reproductive outcomes.     

Mating Compatibility between Geographic Populations of the Seed Beetle <Emphasis Type="Italic">Callosobruchus maculatus</Emphasis>

Allopatric populations sometimes display reproductive barriers in incipient form, and may thus reveal potential mechanisms of speciation. We conducted mating trials to estimate the degree of precopulatory (behavioral) and postcopulatory (gametic) prezygotic isolation between African and Asian populations of the seed beetle Callosobruchus maculatus. The populations differ in several fitness-related traits, and have been associated with different legume hosts. In single-pair trials, the probability of copulation within 10 min was lower when Asian females were paired with African males than it was in the other three pairing combinations. This pairing also provided evidence for gametic isolation, as Asian females mated once to African males laid fewer eggs than did females in the other treatments. Variation in fecundity could not be explained by the duration of copulation, which did not differ among pairing combinations. There was also no effect of pairing combination on the number of copulation attempts, latency to copulation, or rate of egg hatch. When females were simultaneously presented a male from each population, Asian males obtained a disproportionate share of the matings, and were more likely to disturb a pair already in copulo. Surprisingly, male size did not influence the probability of copulation in the single-male trials, the outcome of male–male competition, or the fecundity of once-mated females. Although the African and Asian populations showed some evidence of mating incompatibility, the absence of symmetrical isolating factors suggests minimal barriers to gene flow.     

Old‐male paternity advantage is a function of accumulating sperm and last‐male precedence in a butterfly

Old‐male mating advantage has been convincingly demonstrated in Bicyclus anynana butterflies. This intriguing pattern may be explained by two alternative hypotheses: (i) an increased aggressiveness and persistence of older males during courtship, being caused by the older males' low residual reproductive value; and (ii) an active preference of females towards older males what reflects a good genes hypothesis. Against this background, we here investigate postcopulatory sexual selection by double‐mating Bicyclus anynana females to older and younger males, thus allowing for sperm competition and cryptic mate choice, and by genotyping the resulting offspring. Virgin females were mated with a younger virgin (2–3 days old) and afterwards an older virgin male (12–13 days old) or vice versa. Older males had a higher paternity success than younger ones, but only when being the second (=last) mating partner, while paternity success was equal among older and younger males when older males were the first mating partner. Older males produced larger spermatophores with much higher numbers of fertile sperm than younger males. Thus, we found no evidence for cryptic female mate choice. Rather, the findings reported here seem to result from a combination of last‐male precedence and the number of sperm transferred upon mating, both increasing paternity success.     

Male rank,reproductive behavior,and reproductive success in free-ranging rhesus macaques

Paternity assessment through DNA fingerprinting by synthetic oligonucleotide probes was applied to one birth cohort in a social group of free-ranging rhesus macaques (Macaca mulatta) on Cayo Santiago. The 11 group males and 9 males from other groups were observed mating with the females. Paternity was determined for 11 of the 15 infants. Male dominance rank was not associated with reproductive success. High-ranking resident males (N=5) sired 27% of the infants born during a one-year study. Four of the 11 infants of known paternity were sired by males of other social groups. The four infants of unknown paternity were sired either by males not observed mating with the females or the low-ranking male who was not fingerprinted. Male dominance rank was not associated with reproductive activity during conception cycles. These results suggest that the effect of rank on male reproductive success is not a predictable correlation, but a conditional probability.     

Social group composition modulates the role of last male sperm precedence in post-copulatory sexual selection

In many species, the order in which males mate with a female explains much of the variation in paternity arising from post-copulatory sexual selection. Research in Drosophila suggests that mating order may account for the majority of the variance in male reproductive success. However, the effects of mating order on paternity bias might not be static but could potentially vary with social or environmental factors. To test this idea, we used an existing dataset, collated from an experiment we previously published (Morimoto et al., PLoS One, 11, 2016, e0154468), with the addition of unpublished data from the same experiment. These previous experiments manipulated larval density in Drosophila melanogaster which generated variation in male and female body size, assembled groups of individuals of different sizes, and measured the mating success and paternity share of focal males. The data presented here provides information on each focal male's mating order and the frequency in which focal males remated with same females (‘repetitive matings’). We combined this information with our previously reported focal male reproductive success to partition variance in paternity into male mating order and repetitive matings across groups that differed in the body size composition of males and females. We found, as expected, that male mating order explained a considerable portion of the variance in male paternity. However, we also found that the impact of male mating order on male paternity was influenced by the body size composition of groups. Specifically, males that tended to mate last had a greater paternity advantage, and displayed lower variance, in groups containing a heterogenous mixture male body sizes than in groups with a single male body size. Repetitive mating only had a minor contribution to the variance in male paternity share across all experiments. Overall, our findings contribute to the growing body of research showing that post-copulatory sexual selection is subject to socio-ecological influences.     

Size-mediated dominance and aggressive behavior of male Japanese fluvial sculpin Cottus pollux (Pisces: Cottidae) reduce nest-site abundance and mating success of conspecific rivals

Despite growing evidence for plasticity in the mating patterns of nest-holding animals in relation to the changes in nest abundance, the effects of aggressive interaction by dominant males on nest availability for conspecific rivals remains unclear. To quantify the effects of male–male competition on nest-site choice and mating success of the male Japanese fluvial sculpin Cottus pollux, we conducted experiments on 5 males from different 5 size classes under both sufficient and shortage nest-abundance conditions. Nest-choice experiments showed that both male size class and nest-abundance condition had significant effects on the nesting rates of males. Following the nest-choice experiments, 10 gravid females were added in the experimental tanks. Mating experiments revealed that male size, nesting rate before addition of females, and the number of courtship attempts on females were valid variables of male mating success, regardless of nest-abundance conditions. After achieving initial mating success, the largest nesting male exhibited more frequent aggressive interaction with other conspecific males than he did before obtaining eggs in his nest. Our results suggest that size-mediated dominance and aggressive behavior of males may disrupt nest acquisition of other conspecific males, and may consequently result in extreme variation in mating success among males even under sufficient nest-abundance conditions.     

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.     

Multiple paternity and mating group size in the European earwig,Forficula auricularia

1. The patterns of multiple paternity among the progeny of females are key properties of genetic mating systems. Female multiple mating should evolve due to direct or indirect benefits, but it may also partly be driven by the encounter rate with different potential mates. 2. In this study this hypothesis was experimentally tested in the European earwig (Forficula auricularia L.) by establishing experimental mating groups that differed in the number of males and females (i.e. density). The number of sires and mean sibling relatedness in each clutch were estimated using microsatellite‐based paternity analysis. 3. As predicted, the mean number of sires per clutch was significantly increased, and sibling relatedness decreased, in the higher density treatment where more potential male mates were available. This change was less than proportional to the number of males in the mating groups, indicating that mechanisms limiting multiple paternity in large mating groups were involved. There were no significant relationships between female reproductive success or male siring success with morphology (body size, weight, and forceps size). 4. The present results show that multiple paternity in F. auricularia clutches is partly determined by the availability of male mates and suggest that this effect is modulated by mechanisms in males and/or females that limit multiple paternity.     

Male Mating Tactics in Captive Rhesus Macaques (Macaca mulatta): The Influence of Dominance, Markets, and Relationship Quality

Male mating success in a multimale–multifemale group can depend on several variables: body condition, dominance, coalitions, “friendship,” or an exchange of services for mating access. Exchange patterns may also be determined by market effects or social relationships. We studied the mating tactics of males in a captive, multimale–multifemale group of rhesus macaques and the resulting patterns of mating and paternity to determine the influence of dominance rank, mating markets, and relationship quality on their mating tactics. Male rank was positively related to the total number of copulations and the number of mating partners, but did not explain male mating distribution completely. Moreover, male fertilization success was not related to male rank. Males did not exchange grooming for mating access on the same day and neither the supply nor the rank (as a proxy for quality) of receptive females affected the amount of male grooming, suggesting that market effects did not explain male mating access. However, there was a positive correlation between long-term grooming patterns of both males and females and mating access, indicating that social relationships were important for male mating access. Paternity data revealed that these social relationships were also important for male reproductive success. We conclude that both male rank and male–female “friendship” determined male mating access in these rhesus macaques, but that “friendship” was more important in determining paternity, emphasizing the importance of intersex social bonds in male mating success in multimale primate societies.     

Sperm stratification and paternity success in red flour beetles

Abstract. When females are inseminated by multiple males, male paternity success (sperm precedence) is determined by the underlying processes of sperm storage and sperm utilization. Although informative for many questions, two-male sperm competition experiments may offer limited insight into natural mating scenarios when females are likely to mate with several males. In this study, genetic markers in Tribolium castaneum are used to trace paternity for multiple sires, and to determine whether displacement of stored sperm that occurs after a third mating equally affects both previous mates, or if fertilizations are disproportionately lost by the female's most recent mate. For 20 days after triple-matings, first males retain significantly higher paternity success (relative to first male paternity in double-matings) compared with second males. These results demonstrate that when females remate before sperm mixing occurs, sperm stratification results in differential loss of sperm from the most recent mate. This study provides insight into the mechanisms underlying sperm precedence in a promiscuous mating system, and suggests that T. castaneum females could limit paternity success of particular mates by remating with more highly preferred males.     

Noninvasive paternity assignment in Gombe chimpanzees

The relative success of chimpanzee male mating strategies, the role of male dominance rank and the success of inbreeding avoidance behaviour can only be assessed when paternities are known. We report the probable paternities of 14 chimpanzees included in a long‐term behavioural study of chimpanzees (Pan troglodytes schweinfurthii) at Gombe National Park, Tanzania. DNA samples were collected noninvasively from shed hair and faeces and genotyped using 13–16 microsatellite loci characterized in humans. All 14 offspring could be assigned to fathers within the community. While there is a positive relationship between male rank and reproductive success, we demonstrate that a range of male mating strategies (possessiveness, opportunistic mating and consortships) can lead to paternity across all male ranks. Several adult females were at risk of breeding with close male relatives. Most successfully avoided close inbreeding but in one case a high‐ranking male in the community mated with his mother and produced an offspring. In contrast to recent data on chimpanzees (P. t. verus) from the Taï forest, Côte d’Ivoire, no evidence of extra‐group paternity was observed in our study. Reanalysis of Taï data using a likelihood approach casts doubt on the occurrence of extra‐group paternity in that community as well.     

Application of paternity discrimination by DNA polymorphism to the analysis of the social behavior of primates

Paternity in many primate species cannot be established reliably on behavioral grounds. For instance, Japanese macaques (Macaca fuscata) have a multi-male group structure and promiscuous mating patterns. On the other hand, accurate evaluation of male reproductive success is needed to analyze primate behavior. DNA finger-printing techniques were applied to 2 captive groups of Japanese macaques in the Primate Research Institute of Kyoto University for identification of paternity. Also, mating behavior of a captive group was observed in order to compare the reproductive success of each male with that expected on the basis of his observed mating activity. The number of offspring of full adult males was not related to their social rank although the number of copulations with ejaculation was highly correlated with their social rank. Monitoring of the female sexual cycles from the plasma profiles of gonadotropins and ovarian hormones suggested that males could not choose females at days of ovulation. The results of two-free-ranging wild troops, like those of the captive groups, indicated that high-ranking males could not monopolize the paternity of offspring. The results of paternity discrimination in Japanese macaques were compared with results from patas monkeys (Erythrocebus patas) in a discussion of social structure and male reproductive success. Some aspects of polymorphism detection techniques are also discussed.     

Females decide whether size matters: plastic mate preferences tuned to the intensity of male-male competition

Recent studies have indicated that mating success of large malesmay improve under increasing levels of mating competition. Thisoutcome is explained 1) if male mating competition is overridingfemale preferences for male traits that are unrelated to, ornegatively correlated with, male size and dominance and, inso doing, dictates the distribution of matings or 2) if femalesalter their preferences with respect to large males when male–malecompetition is intense. Under both hypotheses, one could expectlarge, dominant males to be more successful under intense competitionthan under weak competition. However, only the first explanationpredicts that male mating success under intense competitionshould be determined by dominance; traits that are unrelatedto male dominance should be uncorrelated to mating success.In contrast, if females change their preferences (explanation2), males with traits beneficial to females independent of thecompetitive environment can maintain a high mating success underall levels of male–male competition. We tested these alternativesusing a small marine fish, the sand goby, Pomatoschistus minutus.The mating success of large males increased under conditionsallowing intense male competition, whereas females showed apreference for good nest building independent of the level ofcompetition. These findings suggest that females are in controlof their choice by altering their preference for male size inresponse to the intensity of male–male competition ratherthan female preference being overshadowed by male dominance.This plasticity of preferences implies that the strength ofsexual selection is not constant at the population level.     

Pre‐ and postcopulatory sexual selection favor aggressive,young males in polyandrous groups of red junglefowl

A challenge in evolutionary biology is to understand the operation of sexual selection on males in polyandrous groups, where sexual selection occurs before and after mating. Here, we combine fine‐grained behavioral information (>41,000 interactions) with molecular parentage data to study sexual selection in replicated, age‐structured groups of polyandrous red junglefowl, Gallus gallus. Male reproductive success was determined by the number of females mated (precopulatory sexual selection) and his paternity share, which was driven by the polyandry of his female partners (postcopulatory sexual selection). Pre‐ and postcopulatory components of male reproductive success covaried positively; males with high mating success also had high paternity share. Two male phenotypes affected male pre‐ and postcopulatory performance: average aggressiveness toward rival males and age. Aggressive males mated with more females and more often with individual females, resulting in higher sexual exclusivity. Similarly, younger males mated with more females and more often with individual females, suffering less intense sperm competition than older males. Older males had a lower paternity share even allowing for their limited sexual exclusivity, indicating they may produce less competitive ejaculates. These results show that—in these populations—postcopulatory sexual selection reinforces precopulatory sexual selection, consistently promoting younger and more aggressive males.     

Dominance is not always an honest signal of male quality,but females may be able to detect the dishonesty

Females prefer dominant males as mating partners in numerous species. Male dominance rank is considered as an honest signal of male quality, because only healthy males in good condition are thought to be able to win fights with other males. Here, we tested whether activation of the immune system influences the success of males in male–male competition and mating in the field cricket, Gryllus integer. We activated the immune system of males with a nylon monofilament (to mimic a parasitoid larva), and arranged fights between male pairs to assess male dominance and associated mating success. Activation of the immune system with nylon monofilament substantially enhanced the fighting success of males during male–male competition but had no effect on mating success. However, sham-manipulation (a wound only) did not have any effect on fighting success although females mated more often with dominant males. Our study suggests that when male crickets meet an apparent survival threat they may behave more dominantly, probably owing to terminal investment. Male success during male–male competition is not always an honest signal of males’ quality, but females may be able to detect this dishonesty.     

The association between rank,mating effort,and reproductive success in male Barbary macaques (Macaca sylvanus)

The association between social rank, mating effort, and reproductive success of male Barbary macaques (Macaca sylvanus) has been evaluated by longterm behavioral observations and subsequent paternity determination via oligonucleotide DNA fingerprinting in a large semifreeranging group. All offspring born between 1985 and 1988 that survived to at least 1 year of age (n=75) were available for paternity testing. The exclusion of all but one of the potential fathers from paternity was possible in 70 cases (93%). Mating activities were recorded using ad lib. and focal female sampling techniques. The analysis of male mating effort was restricted to the most likely days of conception. Male rank correlated significantly with male mating success in all four breeding seasons and with male reproductive success in three of the four seasons. Mating success and reproductive success also showed a significant correlation, with the exception of one breeding season, in which the proportion of males per fertilizable female was especially high. Poor mating success was almost always associated with poor reproductive success, while good mating success was less predictive for a male's actual reproductive success. This was apparently a consequence of sperm competition, resulting from the promiscuous mating system. Male mating success is not necessarily an unreliable indicator for reproductive success, provided that sufficient sample sizes are available and that conception periods can be determined. Sperm competition and other factors may weaken the association, however.     

Female polyandry affects their sons’ reproductive success in the red flour beetle Tribolium castaneum

A potential benefit to females mating with multiple males is the increased probability that their sons will inherit traits enhancing their pre‐ or post‐mating ability to obtain fertilizations. We allowed red flour beetle (Tribolium castaneum) females to mate on three consecutive days either repeatedly to the same male or to three different males. This procedure was carried out in 20 replicate lines, 10 established with wild‐type, and 10 with the Chicago black morph, a partially dominant phenotypic marker. The paternity achieved by the sons of females from polyandrous vs. monandrous lines of contrasting morph was assessed in the F1, F2 and F3 generation by mating wild‐type stock females to two experimental males and assigning the progeny to either sire based on phenotype. The sons of polyandrous wild‐type females achieved significantly higher paternity when mating in the second male role than the sons of monandrous wild‐type females. By contrast, when mating in the first male role, males produced by females from polyandrous lines tended to have lower paternity than males from monandrous lines. Both effects were independent of the number of mates of the black competitor’s mother, and interacted significantly with the number of progeny laid by the female. These results provide the first evidence that manipulating the number of mates of a female can influence her sons’ mating success and suggest a potential trade‐off between offence and defence in this species.     

Social correlates of fecal testosterone in male ursine colobus monkeys (Colobus vellerosus): the effect of male reproductive competition in aseasonal breeders

Male testosterone (T) levels are thought to be linked with the mating system, degree of parental care, and male–male aggression in reproductive contexts (The ‘challenge hypothesis’; Wingfield et al., 1990). In many species though, T increases associated with mating behavior cannot be separated from those associated with male–male aggression. We tested the challenge hypothesis on aseasonally breeding ursine colobus (Colobus vellerosus), where male–male competition is intense outside of mating contexts. Fecal samples (N = 109) were collected from > 27 subadult and adult males in seven groups during 13-months of research in Ghana in 2004–2005. Fecal T (fT) levels were determined by enzyme immunosorbant assays. Behavioral data was collected using focal-animal and ad libitum sampling. The number of receptive females in each group did not positively correlate with male fT. There was a trend for adult males to have higher fT than subadult males; however there was no effect of rank on fT. The level of male–male aggression experienced was positively correlated with fT and individual males showed higher mean fT during ‘challenge’ than during ‘non-challenge’ periods. The number of male incursions experienced positively correlated with fT whereas the number of between-group encounters did not. Males attempt to gain reproductive opportunities during incursions, thus these results support the ‘challenge hypothesis’ in C. vellerosus. Outside of mating contexts, higher male fT levels are associated with increased aggression. Male parental investment in the form of infant defense was associated with increased fT, rather than the decline expected from other forms of paternal care.