The extent and costs of reproductive interference among four species of true bug

Reproductive interference arises when individuals of one species engage in reproductive activities with individuals of another, leading to fitness costs in one or both species. Reproductive interference (RI) therefore has two components. First, there must be mis-directed mating interactions. Second, there must be costs associated with these mis-directed interactions. Here we consider RI between four species of true bug in the family Lygaeidae, focusing in particular on the fitness consequences to Lygaeus equestris. The species we consider vary in their relationships with each other, including species in the same or different genus, and with or without natural overlap in their geographic ranges. First we show that inter-specific mating interactions, although not a certain outcome, are common enough to perhaps influence mating behaviour in these species (arising in up to 10 % of inter-specific pairings). Second, we show that reproductive interference can seriously reduce female fitness in L. equestris. Importantly, different species impose different costs of RI on L. equestris, with interactions with male Spilostethus pandurus inflicting fitness costs of similar magnitude to the costs of mating with con-specifics. On the other hand, mating interactions with male Oncopeltus fasciatus appear to have no effect on female fitness. In a follow-up experiment, when we allowed competition amongst just females of S. pandurus and L. equestris, the fitness of the latter was not reduced, arguing more strongly for the role of reproductive interference. However, in our final experiments under mass mating conditions with extended ecological interactions (including scope for competition for resources and cannibalism), the costs of RI were less apparent. Our data therefore suggest that the costs of RI will be context-specific and may act in concert with, or be swamped by, other ecological effects. We suggest that comparative studies of this sort that both mimic naturally occurring reproductive interference events, and also artificially generate new ones, will be necessary if we are to better understand the ecological and evolutionary significance of reproductive interference.     

Maintenance of female mimicry as a reproductive strategy in bluegill sunfish (Lepomis macrochirus)

Synopsis In species where male reproductive success is dependent on male competition and aggression, alternative reproductive patterns, thought to represent a reduction in male reproductive effort, sometimes occur. Female mimicry in bluegill sunfish (Lepomis macrochirus) is an example of an obligate alternative male strategy. Female mimics are small, sexually mature males which mimic the details of female behavior, and gain access to functional females attracted to the nests of large, aggressive territorial males. The costs of female mimicry relative to nesting male behavior are discussed and two hypotheses, deception and mutual gain, are presented to explain the tolerance and courtship of female mimics by nesting males.     

Male reproductive strategies in new world primates

Patterns of three variables of reproductive strategies in male New World primates are examined: (i) how males obtain access to potential mates; (ii) how males obtain actual mating opportunities; and (iii) how males affect infant survival and female reproductive success. Male opportunities to associate with females, whether by remaining in their natal groups, dispersing and forming new groups, or dispersing and taking over or joining established groups, are strongly influenced by local population densities and correlate with female reproductive rates and the extent of female reproductive seasonality and synchrony. Differences in male mating success are affected by female accessibility, whether male-male and male-female relationships are hierarchical or egalitarian, and whether female reproduction is seasonally restricted. Patterns of male behavior toward infants, characterized as active assistance, overt interference, or benign tolerance, appear to co-vary with differences in the degree to which males can affect female reproductive rates. These qualitative analyses suggest that the reproductive strategies of male New World primates can be classified along a continuum ranging from conservative to daring depending on whether female reproductive rates are relatively slow or fast and whether reproduction is strongly or weakly linked to seasonal ecological variables. Males adopt the conservative strategy of staying in their natal groups, forfeiting exclusive mating opportunities, and treating infants with tolerance when female reproduction is constrained by ecological factors. Conversely, males adopt the more daring strategy of dispersing and competing when potential payoffs through their ability to affect female reproduction are high.     

Sexual selection and physical attractiveness

Sexual selection processes have received much attention in recent years, attention reflected in interest in human mate preferences. Among these mate preferences are preferences for physical attractiveness. Preferences in and of themselves, however, do not fully explain the nature of the relationships that individuals attain. A tacit negotiation process underlies relationship formation and maintenance. The notion that preferences for physical attractiveness evolved under parasite-driven “good genes” sexual selection leads to predictions about the nature of trade-offs that individuals make between mates’ physical attractiveness and investment potential. These predictions and relevant data are explored, with a primary emphasis on women’s preferences for men’s qualities. In addition, further implications of trade-offs are examined, most notably (a) the impact of environmental variations on the nature of mating and (b) some effects of trade-offs on infidelity and male attempts to control women. The ideas in this paper were substantially influenced by discussions with Kim Hill and Hilly Kaplan following a preliminary presentation of work contained herein at a UNM Human Evolutionary Ecology Program colloquium. Steven W. Gangestad is an associate professor of psychology at the University of New Mexico. His recent research includes work focused on sexual selection in humans and its implications for general relationship phenomena. His other recent research concerns the impact of developmental instability on functional asymmetries, interpersonal orientations, and individual differences in the control of emotional expression.     

Reproductive behavior,egg trading,and correlates of male mating success in the simultaneous hermaphrodite,Serranus tabacarius

Synopsis Serranus tabacarius (Serranidae), the tobaccofish, is a simultaneous hermaphrodite which belongs to a group of seabasses that exhibit a wide variety of social and mating systems. The reproductive behavior of tobaccofish is similar to other hermaphroditic seabasses, with individuals assuming sex-specific spawning behaviors that allow for the assignment of male and female roles in a mating sequence. Virtually all matings involved pairs of individuals, although streaking, an alternative male mating tactic, was observed once. Pairs engage in egg trading, where individuals divide their daily clutch into a series of sequentially released parcels and take turns releasing eggs for their partner to fertilize. Individuals mate over a late afternoon spawning period with a number of partners sequentially. Larger individuals have both more total matings and more spawning partners. Egg trading is not symmetrical, the number of male and female matings for an individual in a spawning sequence is often unequal. Overall, the ratio of male to female matings increases with individual size. Large individuals are socially dominant, chase conspecifics during the reproductive period, and are more likely to end a spawning bout with a partner immediately after mating in the male role. In addition, larger individuals are less likely to reciprocate female matings by a partner, either by only mating once (as a male) in a spawning bout or by mating consecutively as a male within a series of matings. Although larger individuals show this relative specialization in the male role, they maintain their simultaneous hermaphroditism and obtain a substantial percentage of their mating success through female function. Egg trading appears to reduce the opportunity for large individuals to specialize as pure males, and thus interacts with the environmental potential for polygamy in shaping the mating system and sex allocation pattern in this species.     

Male morphological characteristics and mating success in a protogynous coral reef fish, Halichoeres melanurus

Morphological sexual differences and their effects on male mating success were investigated in the tailspot wrasse, Halichoeres melanurus, on a subtropical coral reef of Okinawa, southern Japan. Male mating territories were established along the reef edge from late April to early October, during which time pair-spawning occurred just before sunset in the male territories. Territorial males were larger and brighter than females in this protogynous fish. The males had longer, colorful ventral fins and colorful caudal fins, both of which were used during courtship. Multiple regression analysis of the effects of male characteristics on male mating success revealed that the yellow spot at the pectoral fin base was the most effective. It is suggested that large body size is favored in male–male competition for establishing mating territories and that conspicuous body color is favored in female mate choice. Received: June 16, 1999 / Accepted: September 22, 1999     

Mating strategies in primates: a game theoretical approach to infanticide

Infanticide by newly immigrated or newly dominant males is reported among a variety of taxa, such as birds, rodents, carnivores and primates. Here we present a game theoretical model to explain the presence and prevalence of infanticide in primate groups. We have formulated a three-player game involving two males and one female and show that the strategies of infanticide on the males' part and polyandrous mating on the females' part emerge as Nash equilibria that are stable under certain conditions. Moreover, we have identified all the Nash equilibria of the game and arranged them in a novel hierarchical scheme. Only in the subspace spanned by the males are the Nash equilibria found to be strict, and hence evolutionarily stable. We have therefore proposed a selection mechanism informed by adaptive dynamics to permit the females to transition to, and remain in, optimal equilibria after successive generations. Our model concludes that polyandrous mating by females is an optimal strategy for the females that minimizes infanticide and that infanticide confers advantage to the males only in certain regions of parameter space. We have shown that infanticide occurs during turbulent changes accompanying male immigration into the group. For changes in the dominance hierarchy within the group, we have shown that infanticide occurs only in primate groups where the chance for the killer to sire the next infant is high. These conclusions are confirmed by observations in the wild. This model thus has enabled us to pinpoint the fundamental processes behind the reproductive decisions of the players involved, which was not possible using earlier theoretical studies.     

Phenotypic correlates of male reproductive success in western gorillas

Sexual selection is thought to drive the evolution of sexually dimorphic traits that increase male reproductive success. Despite a large degree of sexual dimorphism among haplorhine primates, phenotypic traits that may influence the reproductive success of males are largely unstudied due to long life spans and the difficulties in quantifying such traits non-invasively. Here we employ digital photogrammetry of body length and crest size, as well as ranking of the gluteal muscle size, to test whether these sexually dimorphic traits are associated with long-term measures of male reproductive success in western gorillas. Among 19 adult male gorillas monitored for up to 12.5 years, we found that all three phenotypic traits were positively correlated with the average number of mates per male, but only crest size and gluteal muscle size were significantly correlated with offspring survival and the annual rate of siring offspring that survive to weaning age. We discuss why such sexually dimorphic traits might be under ongoing selection in gorillas and other species.     

Mating strategy flexibility in the laboratory: Preferences for long- and short-term mating change in response to evolutionarily relevant variables

One of the great challenges for evolutionary psychology has been to explain within-sex individual variation in mating behaviour. Several lines of evidence suggest that some of this variation stems from an adaptation for facultatively increasing or decreasing long- and short-term mating inclinations in response to circumstances. It remains unclear, however, how rapidly such changes can occur, and what stimuli might initiate them. This paper presents three experiments that investigate mating strategy change following exposure to the evolutionarily-relevant stimuli of parental care, resource-abundance, and danger. In each experiment, participants indicated their preferred relationship type (long-term, short-term, or none) for each of fifty other-sex individuals, both before and after priming. Relative to a control group, relationship preferences changed in all three experiments, in directions generally consistent with evolutionary psychological predictions. Moreover, short- and long-term relationship preferences were found to shift independently, such that a change in long-term preference was not accompanied by an opposite change in short-term, or vice versa. Together, these experiments represent the first direct test of the claim that brief interventions can shift the relative strength of people's preferences for long-term and short-term relationships.     

Mating success of alternative maturation phenotypes in male Atlantic salmon,Salmo salar

Summary Mature male parr successfully fertilized eggs of anadromous female Atlantic salmon, Salmo salar, in competition with anadromous males under simulated natural conditions. Mating situations were created in which mature male parr and anadromous males competing for the opportunity to spawn with an anadromous female differed in allelic forms of the same enzyme. Females deposited eggs into a sequence of 3 or 4 eggs nests. The mean proportion of eggs in a redd fertilized by parr increased with increasing numbers of parr present at a redd, reaching 23% at male parr: anadromous male ratios of 20:1. Single male parr fertilized, on average, 5% of the eggs in a redd. The proportion of eggs in an egg nest fertilized by parr also depended upon the order of egg nest construction, such that parr mating success was highest at the initial nest constructed and lowest at the final nest. Parr have relatively high fertilization success for their size when compared with the smaller maturation phenotype of other salmonids.     

The association of three indicators of developmental instability with mating success in humans

Developmental instability (DI) has been proposed to relate negatively to aspects of evolutionary fitness, like mating success. One suggested indicator is fluctuating asymmetry (FA), random deviations from perfect symmetry in bilateral bodily traits. A meta-analytically robust negative association between FA and number of lifetime sexual partners has been previously shown in men and women. We examined the relationship between bodily FA across twelve traits and indicators of quantitative mating success in 284 individuals (141 males, age 19–30 years). Two further indicators of DI, minor physical anomalies (MPAs) and asymmetry in palmar atd angles, were also assessed. For men, no significant associations were detected, whereas for women, unexpected positive relationships of FA with the number of lifetime sexual partners and one-night stands emerged. Thus, in a large sample and using a more highly aggregated FA index, our study fails to replicate previous findings, though equivalence testing also did not support deviation from previous meta-analytic estimates, especially for men. No associations were found for MPAs and FA in atd angles in either sex.     

Experience-dependent recapture rates and reproductive success in male grey mouse lemurs (Microcebus murinus)

Male mating tactics can vary according to the potential for scramble or contest competition but also as a consequence of individual characteristics, such as body condition and previous experience. The influence of experience, i.e., residency, on male recapture rates and reproductive success was studied in a population of free-living grey mouse lemurs. Long-term capture data from 320 individuals revealed that both sexes had very low recapture probabilities within their first year in the study population, but recapture rates declined less sharply during the following years. Capture results and telemetric analyses on 12 focal males revealed that resident males had larger body mass and larger home ranges than new males. Home range size correlated with the number of accessible females, indicating that resident males had higher probabilities to meet mates than new males. The reproductive success of 132 candidate fathers, representing both resident and new males, was determined by means of molecular genotyping. Paternity determination was successful in 38 cases (success rate: 19%). Sixteen resident males and seventeen new males sired offspring. However, in relation to the number of candidate fathers being present in the mating season, resident males were twice as likely to reproduce successfully as new males. These findings suggest experience-dependent reproductive tactics that most likely correspond to a differential spatial knowledge of resources, mates and potential threats. The results generally agree with the predictions made for a scramble competition regime and demonstrate substantial behavioral plasticity in a nocturnal primate species with a dispersed multi-male/multi-female mating system.     

Variance in reproductive success and the opportunity for selection in a serially monogamous species: simulations of the mating system of <Emphasis Type="Italic">Tropheus</Emphasis> (Teleostei: Cichlidae)

Sexual selection is believed to play a major role in speciation processes of cichlid fishes in the East African Great Lakes, in particular Lakes Malawi and Victoria, by driving diversification in male nuptial coloration. In Lake Tanganyika, a high rate of color pattern diversification is found in the genus Tropheus, where more than 100, mostly allopatric, color morphs have been described. Whether color pattern differentiation in Tropheus could follow from sexual selection as well, has not yet been conclusively shown. Unlike typical sexually selected species, Tropheus are sexually monomorphic, establish temporary pair bonds and spawn monogamously. Variance in mating success among individuals would still allow for sexual selection, but due to their high population census sizes, parentage data from natural populations are difficult to obtain. Simulations designed according to existing data on mating behavior in Tropheus suggested that variance in male reproductive success can be substantial and lead to levels of opportunity for selection, which are similar to values estimated, for example, from natural populations of sexually dimorphic songbirds. Variance in male success was mostly affected by the way females perceived and reacted to differences between males, and to a lesser extent by the duration of components of the reproductive cycles of males and females. These results indicate that future work on the importance of sexual selection in Tropheus should concentrate on mate choice cues and female mate choice behavior, but does not depend critically on the acquisition of more detailed life history data.     

Intrasexual competition and canine dimorphism in anthropoid primates.

A number of factors, including sexual selection, body weight, body-weight dimorphism, predation, diet, and phylogenetic inertia have been proposed as influences on the evolution of canine dimorphism in anthropoid primates. Although these factors are not mutually exclusive, opinions vary as to which is the most important. The role of sexual selection has been questioned because mating system, which should reflect its strength, poorly predicts variation in canine dimorphism, particularly among polygynous species. Kay et al. (1988) demonstrate that a more refined estimate of intermale competition explains a large proportion of the variation in canine dimorphism in platyrrhine primates. We expand their analysis, developing a more generalized measure of intermale competition based on the frequency and intensity of male-male agonism. We examine the relative influences of predation (inferred by substrate use), female body weight, body-weight dimorphism, diet, and sexual selection on the evolution of anthropoid canine dimorphism. Intermale competition is very strongly associated with canine dimorphism. Predation also has a marked effect on canine dimorphism, in that savanna-dwelling species consistently show greater canine dimorphism than other species, all other factors being held equal. Body-weight dimorphism is also strongly associated with canine dimorphism, though apparently through a common selective basis, rather than through allometric effects. Body weight seems to play only a minor, indirect role in the evolution of canine dimorphism. Diet plays no role. Likewise, we find little evidence that phylogenetic inertia is a constraint on the evolution of canine dimorphism.     

Mating system in the tarantula spider Eupalaestrus weijenberghi (Thorell, 1894): evidences of monandry and polygyny

The road tarantula Eupalaestrus weijenberghi shows a strongly female-biased sex ratio since adult females live several years while adult males live only for 2 months. In this scenario selective males could be expected. However, several factors such as the rates of reproduction of each sex, degree of sexual selectivity and synchronicity of female receptiveness determine the operational sexual ratio and mating system of the species. Our objective was to determine the mating rates and mating tactics for females and males of E. weijenberghi and their variation throughout the reproductive period. Four hundred sexual encounters among 20 females and 20 males in all possible pair-wise combinations were carried out during 29 days, a brief but intense experimental period, as it also occurs in the field. Mating success differed strongly between sexes. Females mated once: five females mated at the first attempt, eight initially rejected males and copulated in subsequent attempts. Half of the males did not copulate and the others copulated 1-3 times. Mated females actively rejected males. Results indicate a mating system with monogamous females and polygamous males. Not all the females were receptive in every reproductive season. We suggest that female monogamy drastically affects the operational sex ratio, since several females were unreceptive after a single copulation, directly diminishing the male potential reproductive rate. This is the first experimental approach to estimate tarantula mating systems, their determinants and the consequences of the strategies shown by each sex.     

Substance use and mating success

Psychoactive substance use has been typical of most traditional and modern societies and is maintained in the population despite the potential for abuse and related harms, raising the possibility that it (or its underlying causes) confers fitness benefits that offset its costs. Although it seems plausible that psychoactive substances have facilitated survival among ancestral and modern humans, it is not clear that this enhancement has translated into Darwinian fitness through mating and ultimately reproductive success. In the current study, we discuss potential mechanisms by which substance use might make unique contributions to mating success, attend to the possibility that the effects between substance use and mating success are instead confounded, and use structural equations and nationally representative data to determine whether these effects are more likely causal or spurious. Our findings indicate that once we know participants' scores on “third” variables at each round in early young adulthood, their substance use gives us little additional information about their current prospects for acquiring sexual partners and no additional information about of their future prospects. Thus, if adaptations for substance use evolved, their adaptive value does not seem to be found in mating success.     

Mating strategy and reproductive success of male patas monkeys (Erythrocebus patas)

Mating behavior and paternity of offspring of wild patas monkeys were studied at Kala Maloue National Park, Cameroon. Observation of patas groups over three years revealed that multi-male situations occurred after takeover of the position of a resident male. Direct observation of behavior showed that resident males (harem males) occupied only 31% of mating in multi-male situations and 100% in one-male situations. DNA-typing revealed that resident males sired two of four of infants in the one-male situation and four of five in the multi-male situation. Under the two years cycle of the one-male situation and the multi-male situation, calculation shows that resident males sired more offspring than sneakers both in observation and paternity testing. Sneak mating occurred during both one-male and multi-male situations, and resident males performed compensatory mating, with dilution of sneaker sperm; these activities explain the discrepancy found between observation of mating and results of paternity discrimination.     

Maternal influences on the sexual behavior and reproductive success of the female rat

In many species, including humans, there is evidence for parental effects on within-sex variations in reproductive behavior. In the present studies we found that variations in postnatal maternal care were associated with individual differences in female sexual behavior in the rat. Females born to and reared by dams that showed enhanced pup licking/grooming (i.e., High LG mothers) over the first week postpartum showed significantly reduced sexual receptivity and alterations in the pacing of male mounting (i.e., longer inter-intromission intervals) observed in a paced mating test. There were minimal effects on the sexual behavior of the male offspring. The female offspring of High LG mothers showed a reduced lordosis rating, a decreased mount:intromission ratio, received fewer ejaculations and were less likely to achieve pregnancy following mating in the paced mating context. The data suggest maternal influences on the sexual development of the female rat that are functionally relevant for reproductive success. Together with previous studies these findings imply that maternal care can ‘program’ reproductive strategies in the female rat.     

黑眶蟾蜍的两性异形与选型配对模式

本研究以黑眶蟾蜍(Duttaphrynus melanostictus)为研究对象,通过对比黑眶蟾蜍抱对个体的体长、头长、头宽、眼间距、鼓膜径、耳后腺长、眼径、前臂及手长、前肢长以及后肢长等形态特征,分析雌性黑眶蟾蜍繁殖输出与其体型的关系,探究黑眶蟾蜍两性异形模式及其与雌性生育力的关系;同时通过对配对个体形态学特征的相关性分析探究了黑眶蟾蜍的配对模式。结果表明,黑眶蟾蜍雌性体长和体重显著大于雄体;两性的所有局部形态特征均与体长成正相关;去除体长因素影响后,雄性头长以及后肢长均明显大于雌性,其余局部形态特征两性间则皆无显著差异。雌体的窝卵重、窝卵数均与其体长和体重成正相关关系。雌性成体的前肢长与抱对雄性成体的前肢长之间呈显著正相关,其余形态特征两性间均无相关性。研究表明,生育力选择是导致黑眶蟾蜍两性异形的重要驱动力;黑眶蟾蜍的选型配对模式未表现在个体大小上,而是体现在局部特征(前肢长),这不仅为揭示两栖类配对模式的普遍性提供了参考,还表明对两栖类选型配对的研究应以多个性状为对象。     

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 。