Explore the vast range of titles available.

The theoretical literature predicts that parentage differences between the sexes, due to females mating with multiple males, select males to provide less parental care and females to care more for the offspring. We formulate simple evolutionary games to question the generality of this prediction. We find that the relationship between paternal care and fitness gained from extrapair matings is important. A trade-off between these two quantities is required for partial paternity and complete maternity to bias the evolutionary stable strategy (ESS) toward more female care. We argue that this trade-off has been implicitly or explicitly assumed in most previous theories. However, if there is no trade-off between paternal care and extra-pair matings, parentage differences do not influence the ESS sex roles. Moreover, it is also possible for these two quantities to have a positive relationship, in which case we predict selection for male care is possible. We support these predictions using agent-based simulations. We also consider the possibility that caring males have greater opportunities to guard their paternity, and find that this mechanism can also select for male-biased care. Hence, we derive the conditions under which male care may be selected despite partial paternity and complete maternity.

Insects copulate multiple times not only with different mates but also with the same mate, which is called repeated copulation. It occurs as a repeated alternation between copulation and mate‐guarding, leading to the prolonged physical attachment between males and females. Particularly, in species where males forcefully grasp females, attempt to mate without courtship and exhibit repeated copulations, male and female morphological traits are expected to be associated with mating characteristics. In this study, we describe for the first time the detailed mating behaviour and patterns of repeated copulations in the water scorpion Nepa hoffmanni (Nepidae, Hemiptera). Nepa hoffmanni repeated copulation and guarding approximately 10 times on average. Over repeated copulations, copulation duration decreased while guarding duration increased, potentially due to decreased male sperm reserves and increased female mating reluctance. Additionally, we found that average guarding duration was positively associated with male leg length and negatively associated with female leg length. This suggests that shorter male legs may enhance courtship efficiency or intensity, while shorter female legs may be less effective at resisting male mating attempts, leading to a quicker initiation of subsequent copulations with the same partner. This indicates that the evolution of repeated copulations may be linked to the evolution of morphological characteristics. Therefore, our study provides novel insights into the evolution of the mating behaviour of water scorpions. We describe for the first time the detailed mating behaviour and patterns of repeated copulations in the water scorpion Nepa hoffmanni (Nepidae, Hemiptera). Over repeated copulations, copulation duration decreased while guarding duration increased. Additionally, we found that average guarding duration was positively associated with male leg length and negatively associated with female leg length.

Paternity protection and the acquisition of multiple mates select for different traits. The consensus from theoretical work is that mate-guarding intensifies with an increasing male bias in the adult sex ratio (ASR). A male bias can thus lead to male monogamy if guarding takes up the entire male time budget. Given that either female- or male-biased ASRs are possible, why is promiscuity clearly much more common than male monogamy? We address this question with two models, differing in whether males can assess temporal cues of female fertility. Our results confirm the importance of the ASR: guarding durations increase with decreasing female availability and increasing number of male competitors. However, several factors prevent the mating system from switching to male monogamy as soon as the ASR becomes male biased. Inefficient guarding, incomplete last male sperm precedence, any mechanism that allows sperm to fertilize eggs after the male's departure, and (in some cases) the unfeasibility of precopulatory guarding all help explain cases where promiscuity exists on its own or alongside temporally limited mate-guarding. Shortening the window of fertilization shifts guarding time budgets from the postcopulatory to the precopulatory stage.

In web-building spiders, females are often too widely distributed across the landscape for males to monopolize more than one mate. Consequently, males seek females one at a time and may cohabit with females in their webs. Pre-copulatory cohabitation is most common in araneomorphs, which suggests that the first male to mate with a female will have a greater share of paternity than any subsequent mates (first sperm precedence). However, pairs of adult New Zealand sheet-web spiders (Cambridgea foliata (L. Koch, 1872); Desidae) cohabit for longer than required to achieve copulation. This is counter-intuitive as it suggests that males defend females they have already copulated with, in lieu of seeking additional mating opportunities. To investigate the costs and benefits of extended cohabitation on male and female C. foliata, we conducted surveys of webs of solitary and paired males and females. We found that solitary spiders of both sexes consistently position themselves in the center of their webs but that when in pairs, females are displaced from the webs by males and will frequently leave the web altogether. Males in pairs would respond to vibrations simulating prey, while females would not respond. This strongly suggests that extended cohabitation should be costly for females. By contrast, for males, cohabitation is a valuable foraging strategy which, combined with the advantages of mate-guarding, may compensate for any lost mating opportunities due to foregoing searching for further mates.

Passive mechanisms of mate guarding are used by males to promote sperm precedence with little cost, but these tactics can be disadvantageous for their mates and other males. Mated females of the plant bug Lygus hesperus are rendered temporarily unattractive by seminal fluids containing myristyl acetate and geranylgeranyl acetate. These antiaphrodisiac pheromones are gradually released from the female’s gonopore, declining until they no longer suppress male courtship. Because starting quantities of these compounds can vary widely, the repellant signal becomes less reliable over time. Evidence was found of a complimentary mechanism that more accurately conveys female mating status. Once inside the female, geranylgeranyl acetate is progressively converted to geranylgeraniol then externalized. Geranylgeraniol counteracts the antiaphrodisiac effect despite having no inherent attractant properties of its own. This is the first evidence for such an anti-antiaphrodisiac pheromone, adding a new element to the communication mechanisms regulating reproductive behaviors. In many animal species, males guard females to prevent rivals from mating so that they can be sure that they fathered the female’s offspring. Some guarding methods work even when the male is not present. For example, the semen of some male insects contains chemicals known as antiaphrodisiacs that repel other males from females who have recently mated. Over the course of several days or weeks, the females expel or degrade the antiaphrodisiacs, making themselves attractive to other mates again. How long it takes to eliminate the antiaphrodisiacs depends on how much of the chemicals were deposited in the first place. Therefore, males could gain an advantage in fertilizing more eggs by depositing excess antiaphrodisiac to make the females unattractive to other mates for a long time. The Western tarnished plant bug (Lygus hesperus) is an agricultural pest that targets cotton, strawberries and other crops. One antiaphrodisac had already been identified in the semen of male Lygus bugs. To investigate whether the males produced any others, Brent et al. tested the molecules emitted by recently mated females. This search identified another potential antiaphrodisiac. However, females are able to convert this second chemical into a third one that neither attracts nor repels males. This “anti-antiaphrodisiac” acts against the males’ two antiaphrodisiacs, and allows the females to more accurately signal when they are ready to mate again, giving them more control over their reproduction. Anti-antiaphrodisiacs were not previously known to exist, but now that scientists know where to look, more are likely to be found in other species. A better understanding of how different chemicals interact to influence the mating behavior of insects could also lead to new methods of targeting pests of crops, which are safer for the environment than existing chemical pesticides.

A recent study on ladybird, Menochilus sexmaculatus (Fabricius) demonstrates that males perform post-copulatory mate guarding in the form of prolonged mating durations. We investigated whether food resource fluctuation affects pre- and post-copulatory behaviour of M. sexmaculatus . It has not been studied before in ladybirds. For this, adults were subjected to prey resource fluctuations sequentially at three levels: post-emergence (Poe; 10 days), pre-mating (Prm; 24 h) and post-mating (Pom; 5 days; only female). The food resource conditions at each level could be any one of scarce, optimal or abundant. Pre-copulatory and post-copulatory behaviour, and reproductive output were assessed. Post-emergence and pre-mating nutrient conditions significantly influenced the pre-copulatory behaviour. Males reared on scarce post-emergence conditions were found to require significantly higher number of mating attempts to establish mating unlike males in the other two food conditions. Under scarce post-emergence and pre-mating conditions, time to commencement of mating and latent period were high but opposite result was obtained for mate-guarding duration. Fecundity and per cent egg viability were more influenced by post-mating conditions, with scarce conditions stopping oviposition regardless of pre-mating and post-emergence conditions. Present results indicate that pre- and post-copulatory behaviour of ladybird is plastic in nature in response to food resource fluctuations.

The evolution of social monogamy has intrigued biologists for over a century. Here, we show that the ancestral condition for all mammalian groups is of solitary individuals and that social monogamy is derived almost exclusively from this social system. The evolution of social monogamy does not appear to have been associated with a high risk of male infanticide, and paternal care is a consequence rather than a cause of social monogamy. Social monogamy has evolved in nonhuman mammals where breeding females are intolerant of each other and female density is low, suggesting that it represents a mating strategy that has developed where males are unable to defend access to multiple females.

Oxytocin is a central neuromodulator required for facilitating mate preferences for familiar individuals in a monogamous rodent (prairie vole), irrespective of sex. While the role of oxytocin in mate choice is only understood in a few monogamous species, its function in nonmonogamous species, comprising the vast majority of vertebrate species, remains unclear. To address this issue, we evaluated the involvement of an oxytocin homolog (isotocin, referred herein as oxt) in mate choice in medaka fish (Oryzias latipes). Female medaka prefer to choose familiar mates, whereas male medaka court indiscriminately, irrespective of familiarity. We generated mutants of the oxt ligand (oxt) and receptor genes (oxtr1 and oxtr2) and revealed that the oxt-oxtr1 signaling pathway was essential for eliciting female mate preference for familiar males. This pathway was also required for unrestricted and indiscriminate mating strategy in males. That is, either oxt or oxtr1 mutation in males decreased the number of courtship displays toward novel females, but not toward familiar females. Further, males with these mutations exhibited enhanced mate-guarding behaviors toward familiar females, but not toward novel females. In addition, RNA-sequencing (seq) analysis revealed that the transcription of genes involved in gamma-amino butyric acid metabolism as well as those encoding ion-transport ATPase are upregulated in both oxt and oxtr1 mutants only in female medaka, potentially explaining the sex difference of the mutant phenotype. Our findings provide genetic evidence that oxt-oxtr1 signaling plays a role in the mate choice for familiar individuals in a sex-specific manner in medaka fish.

The evolution of monogamy and paternal care in humans is often argued to have resulted from the needs of our expensive offspring. Recent research challenges this claim, however, contending that promiscuous male competitors and the risk of cuckoldry limit the scope for the evolution of male investment. So how did monogamy first evolve? Links between mating strategies and partner availability may offer resolution. While studies of sex roles commonly assume that optimal mating rates for males are higher, fitness payoffs to monogamy and the maintenance of a single partner can be greater when partners are rare. Thus, partner availability is increasingly recognized as a key variable structuring mating behavior. To apply these recent insights to human evolution, we model three male strategies – multiple mating, mate guarding and paternal care – in response to partner availability. Under assumed ancestral human conditions, we find that male mate guarding, rather than paternal care, drives the evolution of monogamy, as it secures a partner and ensures paternity certainty in the face of more promiscuous competitors. Accordingly, we argue that while paternal investment may be common across human societies, current patterns should not be confused with the reason pairing first evolved.