Male burying beetles extend,not reduce,parental care duration when reproductive competition is high

Male parents spend less time caring than females in many species with biparental care. The traditional explanation for this pattern is that males have lower confidence of parentage, so they desert earlier in favour of pursuing other mating opportunities. However, one recent alternative hypothesis is that prolonged male parental care might also evolve if staying to care actively improves paternity. If this is the case, an increase in reproductive competition should be associated with increased paternal care. To test this prediction, we manipulated the level of reproductive competition experienced by burying beetles, Nicrophorus vespilloides (Herbst, 1783). We found that caregiving males stayed for longer and mated more frequently with their partner when reproductive competition was greater. Reproductive productivity did not increase when males extended care. Our findings provide support for the increased paternity hypothesis. Extended duration of parental care may be a male tactic both protecting investment (in the current brood) and maximizing paternity (in subsequent brood(s) via female stored sperm) even if this fails to maximize current reproductive productivity and creates conflict of interest with their mate via costs associated with increased mating frequency.     

Male parental care, female reproductive success, and extrapair paternity

Birds differ considerably in the degree of male parental care,and it has been suggested that interspecific variation in extrapairpaternity is determined by the relative importance of benefitsto females from male parental care and good genes from extrapairsires. I estimated the relationship between extrapair paternityand the importance of male parental care for female reproductivesuccess mainly based on male removal studies, using a comparativeapproach. The reduction in female reproductive success causedby the absence of a male mate was positively correlated withthe male contribution to feeding offspring. The frequency ofextrapair paternity was negatively related to the reductionin female reproductive success caused by the absence of a mate.This was also the case when potentially confounding variablessuch as developmental mode of offspring and sexual dichromatismwere considered. A high frequency of extrapair paternity occursparticularly in bird species in which males play a minor rolein offspring provisioning and in which attractive males providerelatively little parental care. Bird species with frequentextrapair paternity thus appear to be those in which direct fitness benefits from male care are small, females can readilycompensate for the absence of male care, and indirect fitnessbenefits from extrapair sires are important.     

Father absence predicts age at sexual maturity and reproductive timing in British men

Despite the widespread assumption that paternal investment is substantial in our species, previous studies have shown mixed results in relation to the impact of fathers on both offspring survival and reproductive outcomes. Using data from a large representative sample of British men, we tested whether father absence is associated with the timing of reproduction-related events among boys, while controlling for various cues denoting early childhood adversity. We further tested whether the loss of the father at different childhood stages matters, so as to assess whether early life is the most important period or if effects can be seen during later childhood. The results show that father absence before age seven is associated with early reproduction, while father absence between ages 11 and 16 only is associated with delayed voice-breaking (a proxy for puberty), even after adjusting for other factors denoting childhood adversity. We conclude that fathers do exert an influence on male reproductive outcomes, independently of other childhood adversities and that these effects are sensitive to the timing of father absence.     

Prolactin, Oxytocin, and the development of paternal behavior across the first six months of fatherhood

Animal studies have implicated the neuropeptides Prolactin (PRL) and Oxytocin (OT) in processes of maternal bonding and PRL has similarly been shown to play a role in the neurophysiology of fatherhood. Yet, very little is known on the involvement of PRL and OT in human fathering. Forty-three fathers and their firstborn infant were seen twice: in the second and sixth postpartum months. Paternal plasma PRL and OT were sampled at both time-points and analyzed with ELISA methods. At six months fathers were videotaped interacting with their child in social and exploratory play contexts and interactions were micro-analyzed for father-infant Affect Synchrony and father facilitation of child toy exploration. PRL and OT showed high individual stability across time and were correlated at the second observation. PRL was related to father-infant Coordinated Exploratory Play in the toy context whereas OT was associated with father-infant Affect Synchrony in the social context. Results point to the role of PRL and OT in the development of human fathering and underscore their differential relations with patterns of paternal care.     

Androgen levels and social interactions in breeding males of the peacock blenny

Nest-holder male Salaria pavo have lower circulating concentrations of 11-ketotestosterone (KT) at the beginning of the breeding season than at its peak. At that peak density of nesting males was higher as were the number of visits of sneaker males to nests and of agonistic interactions between nest-holders and sneaker males. There was no difference between the two dates either in the frequency of male-male interactions or in the frequency of courtship episodes. Thus, higher plasma levels in nest-holders might be explained by a more intense sneaking pressure at the peak of the breeding season. At that peak, nest-holders had higher plasma levels of KT and a higher testosterone (T) to KT metabolization index in the gonads than did floater males. Both nest-holders and floaters had higher levels of KT and T in the testicular gland than in the testis. The levels of both androgens in the testicular gland, but not in the testis, were correlated with circulating concentrations of KT. These results suggest that the testicular gland is the major source of circulating KT in blenniids. Nest-holders had higher metabolization indexes than floaters both in the testis and in the testicular gland, which suggests that nest holding status promotes the conversion of T into KT.     

Predators, reproductive parasites, and the persistence of poor males on leks

Lekking males are thought to face strong directional selectionon secondary sexual traits. How variation in male traits canpersist under these conditions remains problematic (the lekparadox). Here, we present several game-theoretic models thatshow that avoidance of costly and mobile predators, sneakers,or brood parasites (enemies) leads to variation in female choice.This can result in maintenance of variation in male quality."Enemies" will congregate around higher quality males. Femalesmust then trade-off the benefits of mating with high-qualitymales against the increased risk of enemies. At equilibrium,the models predict a positive correlation between the qualityof a male and the proportions of both enemies and females visitinghim. In the first model, we use this framework to predict thelowest quality male on the lek that will receive any matings.In the second model, we examine the influence of this female-enemygame on the maintenance of variation in male quality. Low-qualitymales are likely to persist when enemies are costly to femalesor occur at high density, and when there is some spatial structureon the lek, so that neighboring males are typically of similarquality. If enemies are more costly to males than to females,high-quality males may benefit from receiving fewer female visits.In the third model, we consider the special case when enemiesare male reproductive parasites. These models illustrate theimportance of considering the simultaneous decisions of multipleplayers in mate choice games.     

Differences in prolactin levels between three alternative male reproductive tactics in striped mice (Rhabdomys pumilio)

In male fishes, birds and mammals, increased prolactin secretion is thought to play a role in species showing paternal behaviours. This hypothesis was investigated in the striped mouse (Rhabdomys pumilio). This paper compares serum prolactin levels in 71 free-living male striped mice following three different reproductive tactics: (i) paternal group-living breeders, (ii) alloparental philopatric group-living males, and (iii) roaming non-paternal solitary males. Prolactin levels of breeding males were significantly higher than that of roamers. Alloparental philopatric males had low prolactin levels, which concur with studies of cooperatively breeding mammals, but contrasts with studies of cooperatively breeding birds. Both breeding males and females showed a decrease in prolactin levels after the breeding season, but not alloparental philopatric males. Prolactin levels were correlated with neither corticosterone levels nor age. These results are in agreement with the hypothesis that prolactin is one proximate mechanism of male reproductive tactics, possibly regulating differences in male parental care.     

Male mating success,sexual size dimorphism,and site fidelity in two species of Malacoctenus (Labrisomidae)

Synopsis In both Malacoctenus hubbsi and Malacoctenus macropus, males defended preferred oviposition sites from both other males and potential egg predators. In M. hubbsi, adult females were larger than adult males. Larger M. hubbsi males were not associated with territory parameters that were correlated with higher mating success, and male size was not correlated with mating success. Male size did affect mating success when territory parameters were statistically controlled for, but the failure of large males to associate with better territories eliminated any mating advantage for larger males. In M. macropus, males are larger than females. Larger males defended preferred oviposition sites, and had higher mating success than did smaller males. Male M. macropus also had much higher site fidelity than male M. hubbsi. These results suggest that the evolution of the differences in site fidelity and sexual size dimorphism between these two species may be due to sexual selection acting differentially in these two species.     

Evolutionary links between reproductive morphology, ecology and mating behavior in opisthobranch gastropods

Sexual coevolution in morphological and behavioral traits has rarely been studied. Using phylogenetic analyses, we explore relationships between sexual characters based on a new molecular phylogeny of 33 opisthobranch taxa (Aglajidae and Gastropteridae). Our measurements of these simultaneous hermaphrodites include male and female reproductive anatomy, mating behavior, and spatial gregariousness. After phylogenetic correction, we found evidence for correlated evolution between male and female reproductive organs such as the size of the seminal fluid producing prostate gland and that of the sperm digesting bursa copulatrix. Our findings suggest that reproductive trait variation is mediated by sexual coevolution, where putatively manipulative male organs evolved in association with female organs involved in sperm selection. Furthermore, low gregariousness was associated with long, reciprocal copulations. We interpret this result as an adaptation to infrequent mate encounters, where it pays to mate longer with and presumably transfer more sperm to a rare partner. Several complex reproductive traits were repeatedly gained or lost across our phylogeny. This pattern is consistent with a scenario in which sexual selection generates dynamic coevolutionary cycles similar to those expected under sexual antagonism. We finally outline approaches for experimentally assessing the proposed functional links that underlie the evolutionary correlations revealed by our study.     

Melodic males and flashy females: Geographic variation in male and female reproductive behavior in red‐eyed treefrogs (Agalychnis callidryas)

Geographic variation in courtship behavior can affect reproductive success of divergent phenotypes via mate choice. Over time, this can lead to reproductive isolation and ultimately to speciation. The Neotropical red‐eyed treefrog (Agalychnis callidryas) exhibits high levels of phenotypic variation among populations in Costa Rica and Panama, including differences in color pattern, body size, and skin peptides. To test the extent of behavioral premating isolation among differentiated populations, we quantified male advertisement calls from six sites and female responses to male stimuli (acoustic and visual signals) from four sites. Our results show that both male advertisement calls and female behavior vary among populations: Discriminant function analyses can predict the population of origin for 99.3% ± 0.7 of males based on male call (dominant frequency and bandwidth) and 76.1% ± 6.6 of females based on female response behavior (frequency and duration of visual displays). Further, female mate choice trials (n = 69) showed that population divergence in male signals is coupled with female preference for local male stimuli. Combined, these results suggest that evolved differences among populations in male call properties and female response signals could have consequences for reproductive isolation. Finally, population variation in male and female behavior was not well explained by geographic or genetic distance, indicating a role for localized selection and/or drift. The interplay between male courtship and female responses may facilitate the evolution of local variants in courtship style, thus accelerating premating isolation via assortative mating.     

Sexual selection in sticklebacks in the field: correlates of reproductive, mating, and paternal success

Male sticklebacks display multiple ornaments, and these ornamentshave been shown to be preferred by females in laboratory experiments.However, few field data exist, and it is not known whether thesepreferences are simultaneously or sequentially operative ina single population. We report correlates of reproductive successin two stickleback populations that differ in their ecology,over several periods within their breeding season. In both populationslarger males had higher reproductive success, but not in all periodsof the breeding season. Reproductive success increased withredness of the throat only in the Wohlensee population, andonly in one period that was characterized by low average success.In the Wohlensee population, the parasitic worm Pomphorhynchuslaevis is abundant, and reproductive success decreased withthe presence of the parasite. In the Roche population, maleswith nests concealed in a plant had higher mating success. Thesenests were less likely to fail, suggesting that females preferredto spawn in concealed nests because of higher offspring survivorship.The different sexual traits appear to reveal different aspectsof male quality (multiple message hypothesis): females probablyfind large males attractive because of their higher paternalquality, but it seems more likely that red males are preferred forbetter genetic qualities. Females also discriminate on territoryquality, and male traits may be important in competition forthese territories. The correlates of reproductive success werenot consistent during the season, probably due to changes inthe availability of ripe females. Such fluctuating selectionpressures will contribute to the maintenance of genetic variationin sexual traits.     

Fertilization mode, sperm characteristics, mate choice and parental care patterns in Artedius spp. (Cottidae)

The reproductive biology of three species in the genus Artedius ( A. harringtoni, A. lateralis and A. fenestralis ) was studied, including parental behaviour, mate choice, fertilization mode, gamete morphology and behaviour, and gonad morphology to help understand the coevolution of reproductive characteristics with potentially different modes of fertilization. In all three species, males guard multiple clutches at oviposition sites. In laboratory mate‐choice experiments, males appearred to prefer to defend sites containing eggs and were better able to attract mates at these sites. There was evidence that internal gomete association, although more pronounced in A. harringtoni , existed in all three species. Sperm behaviour and morphology and histological analysis of gonads suggested that A. fenestralis and A. lateralis were more likely to engage in typical external fertilization. The adoption of eggs and their effect on female mate‐choice patterns appearred to reduce the importance of certainty of paternity in these species, and probably increased the evolutionary stability of male parental care.     

The dynamics of male brooding,mating patterns,and sex roles in pipefishes and seahorses (family Syngnathidae)

Modern theory predicts that relative parental investment of the sexes in their young is a key factor responsible for sexual selection. Seahorses and pipefishes (family Syngnathidae) are extraordinary among fishes in their remarkable adaptations for paternal care and frequent occurrences of sex-role reversals (i.e., female-female competition for mates), offering exceptional opportunities to test predictions of sexual selection theory. During mating, the female transfers eggs into or onto specialized egg-brooding structures that are located on either the male's abdomen or its tail, where they are osmoregulated, aerated, and nourished by specially adapted structures. All syngnathid males exhibit this form of parental care but the brooding structures vary, ranging from the simple ventral gluing areas of some pipefishes to the completely enclosed pouches found in seahorses. We present a molecular phylogeny that indicates that the diversification of pouch types is positively correlated with the major evolutionary radiation of the group, suggesting that this extreme development and diversification of paternal care may have been an important evolutionary innovation of the Syngnathidae. Based on recent studies that show that the complexity of brooding structures reflects the degree of paternal investment in several syngnathid species, we predicted sex-role reversals to be more common among species with more complex brooding structures. In contrast to this prediction, however, both parsimony- and likelihood-based reconstructions of the evolution of sex-role reversal in pipefishes and seahorses suggest multiple shifts in sex roles in the group, independent from the degree of brood pouch development. At the same time, our data demonstrate that sex-role reversal is positively associated with polygamous mating patterns, whereas most nonreversed species mate monogamously, suggesting that selection for polygamy or monogamy in pipefishes and seahorses may strongly influence sex roles in the wild.     

Dimorphic ergatoid males and their reproductive behavior in the ponerine antHypoponera bondroiti

Summary We studied the reproductive behavior of the ponerine antHypoponera bondroiti from Okinawa, Japan. This species has dimorphic wingless ergatoid males (major and minor), dimorphic reproductive females (alate queens and wingless reproductive intercastes), and workers. Workers have neither ovarioles nor spermatheca. Major ergatoid males are the largest colony members. Two major males fought one another in the nest until one disappeared, leaving the other to occupy the nest chambers where queens emerge and mate. Minor ergatoid males also fought one another, although they seemed to be less pugnacious, resulting in occasional cohabitation of multiple minor males in the same nest chamber. Major males never attacked minor ones, allowing them to coexist in the same nest chamber. Minor males seemed to mimic females. Both major and minor males mated with both alate queens and intercastes within the nest. After mating, some alate queens shed their wings and remained in the nest, while the others left the nest for dispersal in the laboratory. Intercastes remained in the nest.     

Reproductive effort of both male and female Bar‐throated Apalis Apalis thoracica is predicted by ornamentation of self and mate

Melanin‐based plumage ornaments have been shown to play an important role in male–male competition, but also influence inter‐sexual communication. Consequently, ornaments may be associated with reproductive effort of both males and females. Females mated to males with larger melanin ornaments may acquire access to better territories or benefit from increased paternal care. Here we investigated whether the melanin‐based breast‐band of male and female Bar‐throated Apalis Apalis thoracica is a signal of information about its bearer and is associated with male and female reproductive effort. Breast‐band size was a highly variable morphometric trait in both sexes, but only in males was it associated with body mass. We then assessed whether male and female breast‐band size predicted maternal and paternal investment. Egg mass increased with male breast‐band size, but decreased with female breast‐band size. Whether females adjust maternal hormone allocation in response to their partner's ornamentation remains a contentious issue. We found that yolk testosterone and androstenedione concentrations were not predicted by male ornamentation or body mass. Finally, males with larger breast‐bands provided their mates with more food, allowing those females to spend more time incubating. Reproductive effort of both parents is therefore predicted by their own and their mate's ornamentation in Bar‐throated Apalis, and thus breast‐band size potentially acts as a signal of reproductive performance in both sexes. These results highlight the need for more comprehensive analyses of a relationship between melanin‐based ornaments and fitness, incorporating multiple behavioural variables associated with reproductive effort.     

Costly parenting: physiological condition over time and season in males of the giant waterbug Abedus dilatatus

Parental care patterns increase offspring fitness but may drive energetic costs to parents. The costs associated with parental care can change over time, decreasing the condition of parents that experience prolonged parental care. Thus, males can modulate parental effort based in the relative fitness cost/benefit pay‐offs under different stages and environmental conditions. The present study assesses the condition of parental males of Abedus dilatatus Say by measuring their lipid, glycogen and carbohydrate contents. We compare the condition in parental males that have experienced recent and prolonged care and that were also collected in the summer and winter. Waterbug males provide parental care via carrying and ventilating eggs on their back. Winter males are smaller and carry fewer eggs compared with summer males. Males with recent care and carrying more eggs present a more lipid content. However, at the end of care, males carrying more eggs present less lipids than males with smaller egg‐pads. Additionally, we find that males collected in the summer present more carbohydrates than males in the winter. Moreover, larger males with prolonged care present less carbohydrates than smaller males, in contrast to males with recent care where there is a positive relationship between size and carbohydrate content. Our results suggest that parental care in A. dilatatus may be a sexually‐selected trait, as has been found in related species, and further experiments could test this idea. This is the first study to provide evidence of physiological costs related to exclusive paternal care in arthropods.     

Residual reproductive value and male mating success: older males do better

Evolution via sexual selection has traditionally been viewed as isolated from life-history constraints. As additionally reproductive resource allocation in males is underexplored, it is rather unclear how life-history factors have shaped lifetime investment into male sexually selected traits. Against this background, we here investigate male butterfly mating success in relation to age, nutritional status, assay condition and wing damage. As predicted, based on a low residual reproductive value, older males had a considerably higher mating success than younger males. Comparisons between virgin and once-mated males suggest that this pattern is related to age per se rather than differential ratings of the resource receptive female. We found no evidence for male body size or condition being important, supporting the notion that in weaponless animals intrinsic motivation is more important for mating success than the differences in physical properties (such as body size or condition). Flight cage experiments suggest that such differences in motivation may be masked under more natural conditions, where flight performance, having a clear impact on mating success (as evidenced by wing manipulation experiments), is likely to be crucial. We conclude that the life-history perspective is a fruitful one for gaining a better understanding of the evolution of sexually selected characters and the predictions derived from contest theory do also apply to male mating success.