Mismatched partners that achieve postpairing behavioral similarity improve their reproductive success.
ABSTRACT: Behavioral similarity between partners is likely to promote within-pair compatibility and to result in better reproductive success. Therefore, individuals are expected to choose a partner that is alike in behavioral type. However, mate searching is very costly and does not guarantee finding a matching partner. If mismatched individuals pair, they may benefit from increasing their similarity after pairing. We show in a monogamous fish species-the convict cichlid-that the behavioral similarity between mismatched partners can increase after pairing. This increase resulted from asymmetrical adjustment because only the reactive individual became more alike its proactive partner, whereas the latter did not change its behavior. The mismatched pairs that increased their similarity not only improved their reproductive success but also raised it up to the level of matched pairs. While most studies assume that assortative mating results from mate choice, our study suggests that postpairing adjustment could be an alternative explanation for the high behavioral similarity between partners observed in the field. It also explains why interindividual behavioral differences can be maintained within a given population.
Project description:In humans, affective states are a key component in pair-bonding, particularly in the early stage of a relationship. Pairing with a high-quality partner elicits positive affective states which, in turn, validate and reinforce the mate choice. Affective states thus strongly affect pair stability and future reproductive success. We propose generalizing the link between affective states and pair-bonding to encompass other monogamous species exhibiting biparental care, chiefly where the reproductive success of the pair critically depends on the coordination between partners. The convict cichlid Amatitlania siquia is a monogamous fish species that forms long-lasting pairs with strong cooperation between parents for parental care. In this species, we showed that females paired with their non-preferred male had lower reproductive success than those paired with their preferred male. We then transposed the judgement bias paradigm, previously used in other animal species, to assess objectively affective states in fishes. Females that were assigned their non-preferred partner exhibited pessimistic bias, which indicates a negative affective state. By contrast, females that were assigned their preferred partner did not exhibit changes in their affective state. Our results highlight that the influence of pair-bonding on affective states is not human-specific and can also be observed in non-human species.
Project description:Monogamy can be either long-term or serial, with new pairs formed with each breeding bout. Costs and benefits are associated with each strategy. Because biparental convict cichlids (Amatitlania nigrofasciata) typically switch mates, exhibiting serial monogamy, we tested for the costs associated with forcing individuals to remain with the same mate. Convict cichlids were observed over two successive breeding bouts, either with the same or a new, equally experienced, mate. Parental behavior did not differ between breeding bouts, nor did brood size. Surprisingly, fish that remained with their original partner for a second bout took significantly longer to produce a brood compared to fish that paired with new partners. New partners were also more likely to successfully produce a second brood than re-mated partners. This is in contrast to the majority of bird studies that show many benefits to staying with the same partner for multiple broods. In convict cichlids, there seems to be no benefit associated with remaining with the same partner and switching mates reduces duration between broods for both males and females, potentially increasing overall reproductive success.
Project description:Pair bonding is generally linked to monogamous mating systems, where the reproductive benefits of extended mate guarding and/or of bi-parental care are considered key adaptive functions. However, in some species, including coral reef butterflyfishes (f. Chaetodonitidae), pair bonding occurs in sexually immature and homosexual partners, and in the absence of parental care, suggesting there must be non-reproductive adaptive benefits of pair bonding. Here, we examined whether pair bonding butterflyfishes cooperate in defense of food, conferring direct benefits to one or both partners. We found that pairs of Chaetodon lunulatus and C. baronessa use contrasting cooperative strategies. In C. lunulatus, both partners mutually defend their territory, while in C. baronessa, males prioritize territory defence; conferring improvements in feeding and energy reserves in both sexes relative to solitary counterparts. We further demonstrate that partner fidelity contributes to this function by showing that re-pairing invokes intra-pair conflict and inhibits cooperatively-derived feeding benefits, and that partner endurance is required for these costs to abate. Overall, our results suggest that in butterflyfishes, pair bonding enhances cooperative defense of prey resources, ultimately benefiting both partners by improving food resource acquisition and energy reserves.
Project description:In monogamous species that exhibit extensive biparental investment, such as termites, both sexes are predicted to be selective when choosing a mate. Size-related traits are expected to be important in partner selection because the fat reserves of the colony founders sustain the incipient colony. Partner relatedness and heterozygosity determine the degree of inbreeding and genetic diversity within the colony and may thus also influence partner selection. To test these predictions, we investigated whether phenotypic and genetic traits influence mate choice and/or competitive advantage during pair formation of Formosan subterranean termites, Coptotermes formosanus (Isoptera: Rhinotermitidae). Pair formation in termites normally occurs within a short period after swarming when alates form tandem pairs on the ground. Alates were collected from 5 light trap samples in the French Quarter of New Orleans, LA. From each sample, both tandem pairs and single individuals were collected and their sex, body weights, and head widths were recorded. Pairwise relatedness and individual levels of heterozygosity were determined by microsatellite genotyping. Males in tandem pairs with females had a significantly larger head width than males that did not form tandem pairs. Weights as well as head widths of tandem running partners were positively correlated. For the majority of the samples, relatedness between tandem partners did not differ from the relatedness to members of the other tandem pairs. Thus, no kin discrimination occurred during tandem running. However, females engaged in tandem running had a higher degree of heterozygosity than females that remained single. These findings suggest partner selection and/or competitive advantage based on size-related phenotypic parameters and genetic diversity. The pairing advantage of heterozygous females might explain previous findings of sex-biased alate production depending on the degree of inbreeding in colonies of several species of the genus Coptotermes.
Project description:Successful captive breeding programs are crucial to the long-term survival of many threatened species. However, pair incompatibility (breeding failure) limits sustainability of many captive populations. Understanding whether the drivers of this incompatibility are behavioral, genetic, or a combination of both, is crucial to improving breeding programs. We used 28 years of pairing data from the San Diego Zoo koala colony, plus genetic analyses using both major histocompatibility complex (MHC)-linked and non-MHC-linked microsatellite markers, to show that both genetic and non-genetic factors can influence mating success. Male age was reconfirmed to be a contributing factor to the likelihood of a koala pair copulating. This trend could also be related to a pair's age difference, which was highly correlated with male age in our dataset. Familiarity was reconfirmed to increase the probability of a successful copulation. Our data provided evidence that females select mates based on MHC and genome-wide similarity. Male heterozygosity at MHC class II loci was associated with both pre- and post-copulatory female choice. Genome-wide similarity, and similarity at the MHC class II DAB locus, were also associated with female choice at the post-copulatory level. Finally, certain MHC-linked alleles were associated with either increased or decreased mating success. We predict that utilizing a variety of behavioral and MHC-dependent mate choice mechanisms improves female fitness through increased reproductive success. This study highlights the complexity of mate choice mechanisms in a species, and the importance of ascertaining mate choice mechanisms to improve the success of captive breeding programs.
Project description:Social behavior can alter the microbiome composition via transmission among social partners, but there have been few controlled experimental studies of gut microbiome transmission among social partners in primates. We collected longitudinal fecal samples from eight unrelated male-female pairs of marmoset monkeys prior to pairing and for 8 weeks following pairing. We then sequenced 16S rRNA to characterize the changes in the gut microbiome that resulted from the pairing. Marmoset pairs had a higher similarity in gut microbiome communities after pairing than before pairing. We discovered sex differences in the degrees of change in gut microbiome communities following pairing. Specifically, the gut microbiome communities in males exhibited greater dissimilarity from the prepairing stage (baseline) than the gut microbiome communities in females. Conversely, females showed a gradual stabilization in the rate of the gut microbiome community turnover. Importantly, we found that the male fecal samples harbored more female-source gut microbes after pairing, especially early in pairing (paired test, P?<?0.05), possibly linked to sex bias in the frequencies of social behavior. From this controlled study, we report for the first time that pair-living primates undergo significant changes in gut microbiome during pairing and that females transmit more microbes to their partners than males do. The potential biases influencing which microbes are transmitted on the basis of sex and whether they are due to sex biases in other behavioral or physiological features need to be widely investigated in other nonhuman primates and humans in the future.IMPORTANCE In this controlled study, we collected longitudinal fecal samples from 16 male and female marmoset monkeys for 2 weeks prior to and for 8 weeks after pairing in male-female dyads. We report for the first time that marmoset monkeys undergo significant changes to the gut microbiome following pairing and that these changes are sex-biased; i.e., females transmit more microbes to their social partners than males do. Marmosets exhibit pair bonding behavior such as spatial proximity, physical contact, and grooming, and sex biases in these behavioral patterns may contribute to the observed sex bias in social transmission of gut microbiomes.
Project description:BACKGROUND:Evidence of multiple genetic criteria of mate choice is accumulating in numerous taxa. In many species, females have been shown to pair with genetically dissimilar mates or with extra-pair partners that are more genetically compatible than their social mates, thereby increasing their offsprings' heterozygosity which often correlates with offspring fitness. While most studies have focused on genetically promiscuous species, few studies have addressed genetically monogamous species, in which mate choice tends to be mutual. RESULTS:Here, we used microsatellite markers to assess individual global heterozygosity and genetic similarity of pairs in a socially and genetically monogamous seabird, the black-legged kittiwake Rissa tridactyla. We found that pairs were more genetically dissimilar than expected by chance. We also identified fitness costs of breeding with genetically similar partners: (i) genetic similarity of pairs was negatively correlated with the number of chicks hatched, and (ii) offspring heterozygosity was positively correlated with growth rate and survival. CONCLUSION:These findings provide evidence that breeders in a genetically monogamous species may avoid the fitness costs of reproducing with a genetically similar mate. In such species that lack the opportunity to obtain extra-pair fertilizations, mate choice may therefore be under high selective pressure.
Project description:Initial mate choice and re-mating strategies (infidelity and divorce) influence individual fitness. Both of these should be influenced by the social environment, which determines the number and availability of potential partners. While most studies looking at this relationship take a population-level approach, individual-level responses to variation in the social environment remain largely unstudied. Here, we explore carry-over effects on future mating decisions of the social environment in which the initial mating decision occurred. Using detailed data on the winter social networks of great tits, we tested whether the probability of subsequent divorce, a year later, could be predicted by measures of the social environment at the time of pairing. We found that males that had a lower proportion of female associates, and whose partner ranked lower among these, as well as inexperienced breeders, were more likely to divorce after breeding. We found no evidence that a female's social environment influenced the probability of divorce. Our findings highlight the importance of the social environment that individuals experience during initial pair formation on later pairing outcomes, and demonstrate that such effects can be delayed. Exploring these extended effects of the social environment can yield valuable insights into processes and selective pressures acting upon the mating strategies that individuals adopt.
Project description: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.
Project description:Stroke survivors often experience social isolation. Social interaction improves quality of life and decreases mortality after stroke. Male mice (20-25 g; C57BL/6N), all initially pair housed, were subjected to middle cerebral artery occlusion (MCAO). Mice were subsequently assigned into one of three housing conditions: (1) Isolated (SI); (2) Paired with their original cage mate who was also subjected to stroke (stroke partner (PH-SP)); or (3) Paired with their original cage mate who underwent sham surgery (healthy partner (PH-HP)). Infarct analysis was performed 72 h after stroke and chronic survival was assessed at day 30. Immediate post-stroke isolation led to a significant increase in infarct size and mortality. Interestingly, mice paired with a healthy partner had significantly lower mortality than mice paired with a stroke partner, despite equivalent infarct damage. To control for changes in infarct size induced by immediate post-stroke isolation, additional cohorts were assessed that remained pair housed for three days after stroke prior to randomization. Levels of brain-derived neurotrophic factor (BDNF) were assessed at 90 days and cell proliferation (in cohorts injected with 5-bromo-2'-deoxyuridine, BrdU) was evaluated at 8 and 90 days after stroke. All mice in the delayed housing protocol had equivalent infarct volumes (SI, PH-HP and PH-SP). Mice paired with a healthy partner showed enhanced behavioral recovery compared with either isolated mice or mice paired with a stroke partner. Behavioral improvements paralleled changes in BDNF levels and neurogenesis. These findings suggest that the social environment has an important role in recovery after ischemic brain injury.