Social selection analysis reveals limited effect of neighbors' traits in Tree swallows.

Social interactions are ubiquitous in nature and can shape fitness of individuals through social selection. This type of selection arises when phenotypes of neighbors influence the fitness of a focal individual. Quantifying social selection is crucial to better characterise the overall selective landscape. For example, if intraspecific competition is strong, traits that are beneficial for an individual could be detrimental for competitors. In this study, we quantified social selection acting on three key ecological traits (body mass, wing length and laying date) in wild Tree swallow (Tachycineta bicolor) females. We used reproductive success measured at three stages throughout the breeding season as fitness proxies to assess selection acting at those decisive moments. We also quantified the effects of environment on selection using measures of conspecifics' density, type of agricultural landscape and presence of interspecific competitors. Overall, we found no strong evidence of social selection on these traits in our study system, although there were marginally non-significant selection gradients suggesting positive effect of larger neighbors. Environmental variables affected reproductive success but did not strongly affect social selection gradients. Our study calls for more social selection estimates to be reported across environments to better understand its importance in wild populations.

Maternal care leads to the evolution of long, slow lives.

Animals, and mammals in particular, vary widely in their "pace of life," with some species living long lives and reproducing infrequently (slow life histories) and others living short lives and reproducing often (fast life histories). These species also vary in the importance of maternal care in offspring fitness: In some species, offspring are fully independent of their mothers following a brief period of nutritional input, while others display a long period of continued dependence on mothers well after nutritional dependence. Here, we hypothesize that these two axes of variation are causally related to each other, such that extended dependence of offspring on maternal presence leads to the evolution of longer lives at the expense of reproduction. We use a combination of deterministic modeling and stochastic agent-based modeling to explore how empirically observed links between maternal survival and offspring fitness are likely to shape the evolution of mortality and fertility. Each of our modeling approaches leads to the same conclusion: When maternal survival has a strong impact on the survival of offspring and grandoffspring, populations evolve longer lives with less frequent reproduction. Our results suggest that the slow life histories of humans and other primates as well as other long-lived, highly social animals such as hyenas, whales, and elephants are partially the result of the strong maternal care that these animals display. We have designed our models to be readily parameterized with demographic data that are routinely collected by long-term researchers, which will facilitate more thorough testing of our hypothesis.

Social interactions generate complex selection patterns in virtual worlds.

Understanding the influence of social interactions on individual fitness is key to improving our predictions of phenotypic evolution. However, we often overlook the different components of selection regimes arising from interactions among organisms, including social, correlational, and indirect selection. This is due to the challenging sampling efforts required in natural populations to measure phenotypes expressed during interactions and individual fitness. Furthermore, behaviours are crucial in mediating social interactions, yet few studies have explicitly quantified these selection components on behavioural traits. In this study, we capitalize on an online multiplayer video game as a source of extensive data recording direct social interactions among prey, where prey collaborate to escape a predator in realistic ecological settings. We estimate natural and social selection and their contribution to total selection on behavioural traits mediating competition, cooperation, and predator-prey interactions. Behaviours of other prey in a group impact an individual's survival, and thus are under social selection. Depending on whether selection pressures on behaviours are synergistic or conflicting, social interactions enhance or mitigate the strength of natural selection, although natural selection remains the main driving force. Indirect selection through correlations among traits also contributed to the total selection. Thus, failing to account for the effects of social interactions and indirect selection would lead to a misestimation of the total selection acting on traits. Dissecting the contribution of each component to the total selection differential allowed us to investigate the causal mechanisms relating behaviour to fitness and quantify the importance of the behaviours of conspecifics as agents of selection. Our study emphasizes that social interactions generate complex selective regimes even in a relatively simple ecological environment.

Socio-economic inequalities in smoking and drinking in adolescence: Assessment of social network dynamics.

AIMS: We investigated whether (1) adolescents selected friends with a similar socio-economic status (SES), (2) smoking and alcohol consumption spread in networks and (3) the exclusion of non-smokers or non-drinkers differed between SES groups. DESIGN: This was a longitudinal study using stochastic actor-oriented models to analyze complete social network data over three waves. SETTING: Eight Hungarian secondary schools with socio-economically diverse classes took part. PARTICIPANTS: This study comprised 232 adolescents aged between 14 and 15 years in the first wave. MEASUREMENTS: Self-reported smoking behavior, alcohol consumption behavior and friendship ties were measured. SES was measured based upon entitlement to an income-tested regular child protection benefit. FINDINGS: Non-low-SES adolescents were most likely to form friendships with peers from their own SES group [odds ratio (OR) = 1.07, 95% confidence interval (CI) = 1.02-1.11]. Adolescents adjusted their smoking behavior (OR = 24.05, 95% CI = 1.27-454.86) but not their alcohol consumption (OR = 1.65, 95% CI = 0.62-4.39) to follow the behavior of their friends. Smokers did not differ from non-smokers in the likelihood of receiving a friendship nomination (OR = 0.98, 95% CI = 0.87-1.10), regardless of their SES. Alcohol consumers received significantly more friendship nominations than non-consumers (OR = 1.16, 95% CI = 1.01-1.33), but this association was not significantly different according to SES. CONCLUSIONS: Hungarian adolescents appear to prefer friendships within their own socio-economic status group, and smoking and alcohol consumption spread within those friendship networks. Socio-economic groups do not differ in the extent to which they encourage smoking or alcohol consumption.

Social causation, social selection, and economic selection in the health outcomes of Chinese older adults and their gender disparities.

Background: The economic selection hypothesis, which argues that the initial economic situation determines both subsequent health and economic conditions, has been drawn into the debate on causation-selection issues. This study aims to construct a path model with self-rated health and depression score of older adults as health outcomes to measure and compare the social causation forces of wealth accumulation, social selection forces of adulthood health, and economic selection forces of childhood economics, and to examine their gender disparities. Methods: Data was obtained from a sample of 19613 older adults aged 45 years or above from the 2014 life history survey and the 2015 routine follow-up survey of the China Health and Retirement Longitudinal Study. Structural equation modeling analysis was conducted employing the full information maximum likelihood estimation method. Results: The presence of social causation, social selection, and economic selection were all statistically supported. In self-rated health, social selection forces held the dominant position, while social causation forces were comparable to economic selection forces. In depression score, social selection still exhibited stronger forces than economic selection, but social causation had forces close to social selection and greater than economic selection. The forces of the three hypotheses in self-rated health did not significantly change with gender, but social causation exerted mightier forces than economic selection within the male group, unlike the female group. The forces of economic selection in depression score were greater in females than males and no significant differences were observed among the forces of the three hypotheses in the female group. Conclusions: Social causation, social selection, and economic selection operate simultaneously on the self-rated health and depression score of older adults. However, the force magnitudes of the three hypotheses and/or their rankings differ by health outcomes and gender.

Evolutionary predictors of the specific colors of birds.

Animal coloration is one of the most conspicuous aspects of human-perceived organismal diversity, yet also one of the least understood. In particular, explaining why species have specific colors (e.g., blue vs. red) has proven elusive. Here, we quantify for nearly all bird species, the proportion of the body covered by each of 12 human-visible color categories, and test whether existing theory can predict the direction of color evolution. The most common colors are black, white, gray and brown, while the rarest are green, blue, purple, and red. Males have more blue, purple, red, or black, whereas females have more yellow, brown, or gray. Sexual dichromatism is partly due to sexual selection favoring ornamental colors in males but not in females. However, sexual selection also correlated positively with brown in both sexes. Strong social selection favors red and black, colors used in agonistic signaling, with the strongest effects in females. Reduced predation risk selects against cryptic colors (e.g., brown) and favors specific ornamental colors (e.g., black). Nocturnality is mainly associated with brown. The effects of habitat use support the sensory drive theory for camouflage and signaling. Darker colors are more common in species living in wet and cold climates, matching ecogeographical rules. Our study unambiguously supports existing theories of color evolution across an entire class of vertebrates, but much variation remains unexplained.

Does capacity to produce androgens underlie variation in female ornamentation and territoriality in White-shouldered Fairywren (Malurus alboscapulatus)?

Historic bias toward study of sex hormones and sexual ornamentation in males currently constrains our perspective of hormone-behavior-phenotype relationships. Resolving how ornamented female phenotypes evolve is particularly important for understanding the diversity of social signals across taxa. Studies of both males and females in taxa with variable female phenotypes are needed to establish whether sexes share mechanisms underlying expression of signaling phenotypes and behavior. White-shouldered Fairywren (Malurus alboscapulatus) subspecies vary in female ornamentation, baseline circulating androgens, and response to territorial intrusion. The moretoni ornamented female subspecies is characterized by higher female, but lower male baseline androgens, and a stronger pair territorial response relative to pairs from the lorentzi unornamented female subspecies. Here we address whether subspecific differences in female ornamentation, baseline androgens, and pair territoriality are associated with ability to elevate androgens following gonadotropin releasing hormone (GnRH) challenge and in response to simulated territorial intrusion. We find that subspecies do not differ in their capacity to produce androgens in either sex following GnRH or simulated territorial intrusion (STI) challenges. STI-induced androgens were predictive of degree of response to territorial intrusions in females only, but the direction of the effect was mixed. GnRH-induced androgens did not correlate with response to simulated intruders, nor did females sampled during intrusion elevate androgens relative to flushed controls, suggesting that increased androgens are not necessary for the expression of territorial defense behaviors. Collectively, our results suggest that capacity to produce androgens does not underlie subspecific patterns of female ornamentation, territoriality, and baseline plasma androgens.

Emergent social structure is typically not associated with survival in a facultatively social mammal.

For social animals, group social structure has important consequences for disease and information spread. While prior studies showed individual connectedness within a group has fitness consequences, less is known about the fitness consequences of group social structure for the individuals who comprise the group. Using a long-term dataset on a wild population of facultatively social yellow-bellied marmots (Marmota flaviventer), we showed social structure had largely no relationship with survival, suggesting consequences of individual social phenotypes may not scale to the group social phenotype. An observed relationship for winter survival suggests a potentially contrasting direction of selection between the group and previous research on the individual level; less social individuals, but individuals in more social groups experience greater winter survival. This work provides valuable insights into evolutionary implications across social phenotypic scales.

Evolution of female colours in birds: The role of female cost of reproduction and paternal care.

Female ornamentation is frequently observed in animal species and is sometimes found as more evolutionary labile than male ornamentation. A complex array of factors may explain its presence and variation. Here we assessed the role of female cost of reproduction and paternal care. Both factors have been pinpointed as important by theoretical studies but have not been investigated yet in details at the interspecific level. We worked on 133 species of North temperate Passeriformes bird species for which both the clutch volume - here taken as the proxy of female cost of reproduction - and amount of paternal care are relatively well known. Using spectrometry, we measured the whole-body coloured plumage patches and quantified three metrics corresponding to brightness (i.e. achromatic component), colour chromaticity (i.e. intensity) and colour volume (i.e. diversity). We found a strong association between male and female colour metrics. Controlling for this association, we found additional small but detectable effects of both cost of reproduction and paternal care. First, females of species with more paternal care were slightly brighter. Second, the interaction between the level of paternal care and egg volume was correlated with female colour intensity: females with more paternal care were more chromatic, with this association mostly present when their investment in reproduction was low. Together these results suggest that female cost of reproduction and paternal care are part of the multiple factors explaining variation of female coloration, besides the strong covariation between male and female coloration.

The social role of song in wild zebra finches.

Male songbirds sing to establish territories and to attract mates.1,2 However, increasing reports of singing in non-reproductive contexts3 and by females4,5 show that song use is more diverse than previously considered. Therefore, alternative functions of song, such as social cohesion3 and synchronization of breeding, by and large, were overlooked even in such well-studied species such as the zebra finch (Taeniopygia guttata). In these social songbirds, only the males sing, and pairs breed synchronously in loose colonies,6,7 following aseasonal rain events in their arid habitat.8,9 As males are not territorial, and pairs form long-term monogamous bonds early in life, conventional theory predicts that zebra finches should not sing much at all; however, they do and their song is the focus of hundreds of lab-based studies.10,11,12,13,14,15,16,17,18,19,20,21,22 We hypothesize that zebra finch song functions to maintain social cohesion and to synchronize breeding. Here, we test this idea using data from 5 years of field studies, including observational transects, focal and year-round audio recordings, and a large-scale playback experiment. We show that zebra finches frequently sing while in groups, that breeding status influences song output at the nest and at aggregations, that they sing year round, and that they predominantly sing when with their partner, suggesting that the song remains important after pair formation. Our playback reveals that song actively features in social aggregations as it attracts conspecifics. Together, these results demonstrate that birdsong has important functions beyond territoriality and mate choice, illustrating its importance in coordination and cohesion of social units within larger societies.

The evolution of sex similarities in social signals: Climatic seasonality is associated with lower sexual dimorphism and greater elaboration of female and male signals in antbirds (Thamnophilidae).

Selection on signals that mediate social competition varies with resource availability. Climate regulates resource availability, which may affect the strength of competition and selection on signals. Traditionally, this meant that more seasonal, colder, or dryer-overall harsher-environments should favor the elaboration of male signals under stronger male-male competition, increasing sexual dimorphism. However, females also use signals to compete; thus, harsher environments could strengthen competition and favor elaboration of signals in both sexes, decreasing sexual dimorphism. Alternatively, harsher environments could decrease sexual dimorphism due to scarcer resources to invest in signal elaboration in both sexes. We evaluated these contrasting hypotheses in antbirds, a family of Neotropical passerines that varies in female and male signals and occurs across diverse climatic regimes. We tested the association of sexual dimorphism of plumage coloration and songs with temperature, precipitation, and their seasonality. We found that greater seasonality is associated with lower sexual dimorphism in plumage coloration and greater elaboration of visual signals in both sexes, but not acoustic signals. Our results suggest that greater seasonality may be associated with convergent elaboration of female and male visual signals, highlighting the role of signals of both sexes in the evolution of sexual dimorphism.

Examining Social Influences on Why We Drink: Perceived Drinking Motives in the Social Network Impact Individuals' Own Drinking Motives and Alcohol Use.

Introduction: A significant body of research has investigated the impacts of social influence and social selection on binge drinking and risk factors for binge drinking in emerging adults; however, one risk factor for binge drinking that has yet to be thoroughly investigated in this regard is drinking motives. Preliminary research suggests the motives of others may impact emerging adults' own alcohol use indirectly through their own motives (i.e., social influence). While these are important findings, research to date has been only conducted with adolescents or dyads and has not examined selection (i.e., selecting social network members with similar motives). We filled these gaps with a longitudinal egocentric social network design. Methods: Emerging adults (N = 177) completed measures on their alcohol use, drinking motives, and social networks at baseline (T1) and four-month follow-up (T2). Results: A cross-lagged panel model indicated T1 perceived network drinking motives predicted T2 participant drinking motives (for all motives but social), but T1 participant drinking motives did not predict T2 perceived network drinking motives. Path analysis indicated T1 perceived network drinking motives predicted T2 participant binge drinking frequency indirectly through T2 participant drinking motives for enhancement, coping-with-anxiety, and conformity, but not social or coping-with-depression, motives. Discussion: Results suggests drinking motives of those around emerging adults impact their own drinking motives, and indirectly, their own alcohol use. We found evidence of social influence, but not social selection. Conclusion: It appears that those around emerging adults have the capacity to influence their drinking behaviors and drinking motives.

Sexual selection, feather wear, and time constraints on the pre-basic molt explain the acquisition of the pre-alternate molt in European passerines.

Avian feathers need to be replaced periodically to fulfill their functions, with natural, social, and sexual selection presumably driving the evolution of molting strategies. In temperate birds, a common pattern is to molt feathers immediately after the breeding season, the pre-basic molt. However, some species undergo another molt in winter-spring, the pre-alternate molt. Using a sample of 188 European passerine species, Bayesian phylogenetic mixed models, and correlated evolution analyses, we tested whether the occurrence of the pre-alternate molt was positively associated with proxies for sexual selection (sexual selection hypothesis) and nonsexual social selection (social selection hypothesis), and with factors related to feather wear (feather wear hypothesis) and time constraints on the pre-basic molt (time constraints hypothesis). We found that the pre-alternate molt was more frequent in migratory and less gregarious species inhabiting open/xeric habitats and feeding on the wing, and marginally more frequent in species with strong sexual selection and those showing a winter territorial behavior. Moreover, an increase in migratory behavior and sexual selection intensity preceded the acquisition of the pre-alternate molt. These results provide support for the feather wear hypothesis, partial support for the sexual selection and time constraints hypotheses, and no support for the social selection hypothesis.

Intraspecific variation and directional casque asymmetry in adult southern cassowaries (Casuarius casuarius).

The cranial casques of modern cassowaries (Casuarius) have long intrigued researchers; however, in-depth studies regarding their morphological variation are scarce. Through visual inspection, it has been recognized that casque variability exists between conspecifics. Understanding casque variation has both evolutionary and ecological importance. Although hypothesized to be targeted by selection, intraspecific casque variation has not been quantified previously. Through a large sample of C. casuarius (n = 103), we compared casque shape (lateral and rostral views) between sexes and between individuals from non-overlapping geographical regions using two-dimensional (2D) geometric morphometrics. We found no statistically significant differences between the casque shape of females and males and few substantial shape differences between individuals from different geographic areas. Much of the intraspecific variation within C. casuarius is due to casque asymmetries (77.5% rightward deviating, 20.7% leftward deviating, and 1.8% non-deviating from the midline; n = 111), which explain the high variability of southern cassowary casque shape, particularly from the rostral aspect. Finally, we discuss how our non-significant findings implicate social selection theory, and we identify the benefits of quantifying such variation for further elucidating casque function(s) and the social biology of cassowaries.

Experimental data exploring the effects of intranasal oxytocin on young adult social preference and attachment to romantic partners, parents, friends, and strangers.

Experimental studies exploring the effects of intranasal oxytocin are typically underpowered due to small samples. Open access to experimental data and procedures and the use of previously employed measures is critical to building more robust and replicable findings, especially in less studied areas of oxytocin research. In this paper, data is provided from a double-blind placebo-controlled crossover study exploring the effects of intranasal oxytocin (IN-OT: 24 IU) on social preference to romantic partners, parents, peers, and strangers. Young adults (N = 44; 91% female) in committed dating relationships completed three phases of data collection including a screening survey followed by two cmd kwdnextpage ?>laboratory visits. In addition to romantic partner-, and stranger attraction ratings, the data is the first to provide comparisons between attachment and social preference ratings to parents, close friends, and romantic partners under placebo and IN-OT conditions. The data also include differences by situational and life history factors known to moderate oxytocin effects. The detailed protocol, and dataflow can be accessed to verify the analysis and findings or to conduct a replication study. The standardized experimental design and common IN-OT protocol add to the capacity for a meta-analysis exploring oxytocin effects on partner preference and may also be directly ported to existing or future studies with related questions to increase sample size and power.

Gender roles and selection mechanisms across contexts: a comparative analysis of the relationship between unemployment, self-perceived health and gender.

Health literature shows that unemployment has a gendered effect on health. However, whether men or women are more affected and why remains unclear. We assume that unemployment harms women less than men because of two mechanisms: social roles theories and health selection. First, the availability and centrality in individuals' lives of roles other than employment may reduce the detrimental effect of unemployment for women. Second, the gendered impact of unemployment on health results from the different ways selection mechanisms operate across genders. Moreover, these two mechanisms may operate differently in different contexts - for example, across different gender regimes. We investigate this by pursuing a three-step comparative approach. The analysis relies on EU-SILC data covering Italy and Sweden for 2004 to 2015 and SOEP data for Germany (1995-2017) and applies correlated dynamic random-effects probit models. While we find weak support for the role of health selection in shaping the relations between unemployment, health, and gender, our empirical results are in line with the hypothesis of a larger gendered effect in older (vs younger) cohorts, western (vs eastern) Germany and Italy (vs. Sweden). Future empirical research needs to directly address the role of gender regimes in moderating such complex relationships.

A Synthesis of Game Theory and Quantitative Genetic Models of Social Evolution.

Two popular approaches for modeling social evolution, evolutionary game theory and quantitative genetics, ask complementary questions but are rarely integrated. Game theory focuses on evolutionary outcomes, with models solving for evolutionarily stable equilibria, whereas quantitative genetics provides insight into evolutionary processes, with models predicting short-term responses to selection. Here we draw parallels between evolutionary game theory and interacting phenotypes theory, which is a quantitative genetic framework for understanding social evolution. First, we show how any evolutionary game may be translated into two quantitative genetic selection gradients, nonsocial and social selection, which may be used to predict evolutionary change from a single round of the game. We show that synergistic fitness effects may alter predicted selection gradients, causing changes in magnitude and sign as the population mean evolves. Second, we show how evolutionary games involving plastic behavioral responses to partners can be modeled using indirect genetic effects, which describe how trait expression changes in response to genes in the social environment. We demonstrate that repeated social interactions in models of reciprocity generate indirect effects and conversely, that estimates of parameters from indirect genetic effect models may be used to predict the evolution of reciprocity. We argue that a pluralistic view incorporating both theoretical approaches will benefit empiricists and theorists studying social evolution. We advocate the measurement of social selection and indirect genetic effects in natural populations to test the predictions from game theory and, in turn, the use of game theory models to aid in the interpretation of quantitative genetic estimates.

Social Selection and the Evolution of Maladaptation.

Evolution by natural selection is often viewed as a process that inevitably leads to adaptation or an increase in population fitness over time. However, maladaptation, an evolved decrease in fitness, may also occur in response to natural selection under some conditions. Social selection, which arises from the effects of social partners on fitness, has been identified as a potential cause of maladaptation, but we lack a general rule identifying when social selection should lead to a decrease in population mean fitness. Here we use a quantitative genetic model to develop such a rule. We show that maladaptation is most likely to occur when social selection is strong relative to nonsocial selection and acts in an opposing direction. In this scenario, the evolution of traits that impose fitness costs on others may outweigh evolved gains in fitness for the individual, leading to a net decrease in population mean fitness. Furthermore, we find that maladaptation may also sometimes occur when phenotypes of interacting individuals negatively covary. We outline the biological situations where maladaptation in response to social selection can be expected, provide both quantitative genetic and phenotypic versions of our derived result, and suggest what empirical work would be needed to test it. We also consider the effect of social selection on inclusive fitness and support previous work showing that inclusive fitness cannot suffer an evolutionary decrease. Taken together, our results show that social selection may decrease population mean fitness when it opposes individual-level selection, even as inclusive fitness increases.

The singing question: re-conceptualizing birdsong.

Birdsong has been the subject of broad research from a variety of sub-disciplines and has taught us much about the evolution, function, and mechanisms driving animal communication and cognition. Typically, birdsong refers to the specialized vocalizations produced by oscines. Historically, much of the research on birdsong was conducted in north temperate regions (specifically in Europe and North America) leading to multiple biases. Due to these historic biases these vocalizations are generally considered to be highly sexually dimorphic, heavily shaped by sexual selection and essential for courtship and territoriality. Song is also typically defined as a learned trait shaped by cultural evolution. Together, this framework focuses research specifically on males, particularly during the north temperate breeding season - reflecting and thereby reinforcing this framework. The physiological underpinnings of song often emphasize the role of the hypothalamic-pituitary-gonadal axis (associated with breeding changes) and the song control system (underlying vocal learning). Over the years there has been great debate over which features of song are essential to the definition of birdsong, which features apply broadly to contexts outside males in the north temperate region, and over the importance of having a definition at all. Importantly, the definitions we use can both guide and limit the progress of research. Here, we describe the history of these definitions, and how these definitions have directed and restricted research to focus on male song in sexually selected contexts. Additionally, we highlight the gaps in our scientific knowledge, especially with respect to the function and physiological mechanisms underlying song in females and in winter, as well as in non-seasonally breeding species. Furthermore, we highlight the problems with using complexity and learning as dichotomous variables to categorize songs and calls. Across species, no one characteristic of song - sexual dimorphism, seasonality, complexity, sexual selection, learning - consistently delineates song from other songbird vocal communication. We provide recommendations for next steps to build an inclusive information framework that will allow researchers to explore nuances in animal communication and promote comparative research. Specifically, we recommend that researchers should operationalize the axis of variation most relevant to their study/species by identifying their specific question and the variable(s) of focus (e.g. seasonality). Researchers should also identify the axis (axes) of variation (e.g. degree of control by testosterone) most relevant to their study and use language consistent with the question and axis (axes) of variation (e.g. control by testosterone in the seasonal vocal production of birds).

Understanding the association between material hardship and posttraumatic stress disorder: a test of the social selection and social causation hypotheses and an exploration of gender differences.

PURPOSE: There is a well-established association between poverty and posttraumatic stress disorder (PTSD); however, little research has tested the temporality of the association. METHODS: Using data from Waves IV (2008; N = 14,800) and V (2016-2018; N = 10,685) of the National Longitudinal Study of Adolescent to Adult Health, we examined temporal associations between material hardship (a specific operationalization of poverty) and PTSD, as well as assessed for potential gender differences in associations. We conducted logistic regression and generalized structural equation modeling to examine associations between material hardship and PTSD and assess for mediation and moderation by gender. RESULTS: Prior PTSD diagnoses were associated with an increased likelihood of material hardship (OR = 1.64; 95% CI 1.21, 2.21). The indirect effect of gender on material hardship through PTSD diagnoses was significant. Prior material hardship was associated with an increased likelihood of PTSD diagnoses (OR = 1.81; 95% CI 1.35, 2.42). The indirect effect of gender on PTSD diagnoses through material hardship was significant. There was no evidence of moderation by gender for either association. CONCLUSION: Results suggest reciprocal associations between material hardship and PTSD. Economic policies, as well as improved access to evidence-based PTSD treatments, may reduce the burden of both material hardships and PTSD.