Reproductive Payoffs Research Articles

Reproductive payoffs of territoriality are snow‐dependent in a mountain ungulate, the Alpine chamois

AbstractFemale density and distribution are dependent on resource phenology and female availability strongly influences male mating behaviour and success. When a male adopts a ‘resource defence’ tactic, his reproductive success depends on the location and attractiveness of his territory. Environmental factors associated with territory quality are expected to influence mating success, for example, through territory features or male–male competition. In a protected population of a mountain‐dwelling polygynous herbivore, the Alpine chamois Rupicapra r. rupicapra, we investigated the relationships among mating opportunities, some environmental variables (snow depth, topographic features and size of territories) and male intra‐sexual competition for mating. We recorded the mating behaviour and territory size of 15 GPS‐GSM radio‐tagged territorial males, during five rutting seasons (early November to early December: N = 8 individuals in 2011, N = 9 in 2012, N = 8 in 2015, N = 11 in 2016, N = 7 in 2017; 80% of them were observed for more than one mating season) and related them to snow depth and topography of territories. In ruts with deep snow cover, territorial males had smaller territories and higher number of mating opportunities than in ruts with lower snow cover. Smaller territories showed the highest values of terrain roughness, in turn with little or no snow cover in the mating season, and were visited by a greater number of females, than larger territories. Number of wins was positively influenced by snow depth and negatively related to the frequency of aggressions. The frequency of male–male aggressive interactions was greater during ruts with deep snow cover and for males with territories at higher elevations; additionally, it was negatively related to interactions won. Thus, snow depth, which influences resource distribution and female movements, is confirmed as a strong determinant of male mating opportunities and mating behaviour.

Male reproductive adjustments to an introduced nest predator

AbstractNest predation has a large impact on reproductive success in many taxa. Defending offspring from would-be predators can also be energetically and physiologically costly for parents. Thus, to maximize their reproductive payoffs, individuals should adjust their reproductive behaviors in relation to the presence of nest predators. However, effects of nest predator presence on parental behaviors across multiple reproductive contexts remain poorly understood, particularly in non-avian taxa. We ran a series of experiments to test how the presence of an egg predator, the invasive rockpool shrimp, Palaemon elegans, influences male reproductive decisions and egg survival in a species of fish with exclusive paternal care, the three-spined stickleback, Gasterosteus aculeatus. We found that, in the presence of shrimp, male sticklebacks were less likely to build a nest, invested less in territory defense against an intruder, and tended to fan eggs in their nest less and in shorter bouts, but did not alter their investment in courtship behavior. The predator’s presence also did not affect egg survival rates, suggesting that males effectively defended their brood from the shrimp. These results show that reproducing individuals can be highly responsive to the presence of nest predators and adjust their behavioral decisions accordingly across a suite of reproductive contexts.

The Collective Action Problem but Not Numerical Superiority Explains Success in Intergroup Encounters in Verreaux’s Sifaka (Propithecus verreauxi): Implications for Individual Participation and Free-Riding

Socioecological theory predicts that larger groups are able to gain better access to resources because of their numerical advantage in intergroup contests. Nevertheless, the numerical superiority hypothesis has received mixed support, perhaps due to the collective action problem and sex differences in strategies and payoffs. We tested the numerical superiority and the collective action problem hypotheses using 141 intergroup encounters in a 7-year dataset on 5 groups of Verreaux’s sifaka (Propithecus verreauxi) at Ankoatsifaka Research Station in Kirindy Mitea National Park in western Madagascar. Contrary to the numerical superiority hypothesis, larger groups were not more likely to supplant smaller groups, nor was success determined by participation of a larger number of one sex. Consistent with a collective action problem, group size negatively affected participation. Notably, the sexes differed in which factors predicted individual participation. Male participation, which may serve to defend mating opportunities with resident females and signal competitive ability to neighboring groups, was greater than female participation, though we did not detect any strong predictor of male participation. Female participation was more likely during the lactation season, when food resources were scarce, than during the mating season. Contrary to previous studies, which argued that mothers with infants avoid intergroup conflicts because of the risk of infanticide, our study suggests that maternal energetic stress due to lactation and food scarcity increases the benefits of defending resources and instead drives mothers to participate in intergroup encounters. Thus, individual reproductive payoffs provide the private incentives needed to induce collective action.

Predator defense is shaped by risk, brood value and social group benefits in a cooperative breeder

AbstractPredation is a major cause of mortality and nest failure in birds. Cooperative predator defense can enhance nest success and adult survival but, because it is inherently risky, dynamic risk assessment theory predicts that individuals modify defense behavior according to the risk posed by the predator. Parental investment theory, on the other hand, predicts that reproductive payoffs (brood value) determine investment in nest defense. We propose that, in cooperative breeders, fitness benefits deriving from the survival of other group members may additionally influence defense behavior (social group benefits theory). We tested predictions of these theories in the cooperatively breeding purple-crowned fairy-wren, Malurus coronatus, where brood value is higher for breeders, but social group benefits more important for helpers. We recorded experimentally induced individual defense behaviors in response to predator models presented near nests, representing differing levels of threat to nests and adults. As predicted, 1) individuals engaged in less risky defenses when encountering a more dangerous predator (dynamic risk assessment theory); 2) individuals defended older broods more often, and breeders defended more than helpers (parental investment theory); and 3) helpers were more likely to respond to a predator of adults (social group benefits theory). Our findings highlight that predator defense in cooperative breeders is complex, shaped by the combination of immediate risk and multiple benefits.

Temporal variation in reproductive costs and payoffs shapes the flowering strategy of a neotropical milkweed, Asclepias curassavica

AbstractA central goal of evolutionary ecology is to understand the factors that select for particular life history strategies, such as delaying reproduction. For example, environmental variation and reproductive costs to survival and growth often select for reproductive delays in semelparous and iteroparous species. In this study, we examine how variation in reproductive cost, which we define as a reduction to growth, survival, or future reproduction after a reproductive event, may select for reproductive delay in an iteroparous Neotropical milkweed with no obvious reproductive season. We analyzed demographic data collected every 3 months for 3 years from four populations of Asclepias curassavica in Monteverde, Costa Rica. We detected costs of flowering to survival and growth that varied in magnitude between our 12 transition periods without a seasonal pattern. The populations also exhibited temporal variation in reproductive payoffs measured as seedling establishment. We incorporated these reproductive costs into demographic projection models, which predicted a delayed flowering strategy only when we included temporal variation in costs and payoffs. Temporal variation in reproductive costs and payoffs is an important selective force in the evolution of delayed flowering in iteroparous species. Further, a lack of predictable seasonal pattern to reproductive costs and payoffs may contribute to the lack of seasonal reproductive patterns observed in our study species and other Neotropical species.

Space use and its effects on reproductive success of anadromous Atlantic salmon

We combined habitat mapping, radio tracking of adults, redd mapping, and genetic parentage analysis on juveniles for 2 consecutive years to test eight predictions on the reproductive payoffs and individual features associated with space use tactics of anadromous Atlantic salmon (Salmo salar) in a natural population. Regarding payoffs, we found that (1) males settled in better habitat, visited more redds, and tended to get more mates than males settled in poorer habitat; (2) they also sired more offspring; (3) the latter effect was stronger in the first year, when redds were more aggregated; and (4) female reproductive success increased with habitat quality in their home range, especially in the first year. For individual features, (5) individuals that settled earlier in their home range had better habitat for juvenile production, but only in the first year; (6) females were less mobile than males, especially in the second year; (7) larger males did not settle in better habitats than smaller males; and (8) smaller males were not more mobile than larger males.

What Explains Patrilineal Cooperation?

Evolutionary anthropologists have proposed that unilineal kinship promotes collective action and that patriliny occurs when the reproductive payoff from passing wealth to sons is greater than that for daughters. We assess both of these theoretical perspectives as well as indirect reciprocity and kin selection as possible contributors to patrilineal cooperation in the Dogon of Mali. The mean coefficient of relatedness for males (N = 4,724) in 31 Dogon patrilineages is r = 0.03, which is very low (akin to second cousins). However, relatedness in the 638 work-eat groups (WEGs) that make up the patrilineages is very high (r = 0.32), or greater than for half siblings. Indirect reciprocity and collective action explain cooperation among fictive kin in the patrilineage as a whole: the old men at the apex of the lineage help to stabilize cooperation by using their gerontocratic authority to punish cheaters. However, kin selection is a more useful theory for explaining cooperative behavior within WEGs, and both qu...

Effect of immune challenge on aggressive behaviour: how to fight two battles at once

Animals are attacked by pathogens, predators and competitors, sometimes simultaneously. For example, male crickets fight each other for access to females and such challenges may occur when one or both males are also defending themselves against a pathogen. We tested whether males altered their aggressive motivation when faced with both a competitor and a pathogen simultaneously. We found that immune-challenged male crickets (Gryllus texensis) were more likely to defeat male competitors when the reproductive payoff (i.e. a female) was nearby. However, when females were not present, males showed a decrease in their aggressive behaviour, and were less likely to win encounters with control males. This plasticity of aggressive motivation did not occur when males were chronically immune challenged. Chronically immune-challenged males were more likely to be defeated by control males regardless of the presence of a female. These results suggest that the costs associated with a chronic immune challenge may prevent terminal reproductive investment. We show that males can benefit from terminal reproductive investment because acutely immune-challenged males were still capable of mating and females did not appear to discriminate against them. Male crickets appear to engage in a context-dependent trade-off between the ability to defeat pathogens and the ability to defeat competitors. This trade-off is mediated, in part, by changes in male aggressive motivation (i.e. the critical threshold for the decision to flee).

Sequential male mate choice under sperm competition risk.

Male eagerness to mate is a central paradigm of sexual selection theory. However, limited sperm supplies mean that male sexual restraint might sometimes be favored under promiscuous mating. Here, we demonstrate dynamic plasticity in male mating effort when females are encountered sequentially under varying sperm competition risk. Rather than showing consistent eagerness to mate, male house mice (Mus musculus domesticus) instead tailor their mating effort according to likely reproductive payoffs. They are significantly less likely to mate when sperm competition is certain and potential reproductive payoffs low, but dramatically increase investment if they do choose to mate under such circumstances. By contrast, male mice are significantly more likely to mate in situations simulating extra-territorial copulations, where future risk of competition is high but so too are potential reproductive rewards. Differential mating propensity appears to be the primary mechanism by which male house mice allocate sperm adaptively under sperm competition risk because we find no evidence for facultative adjustment of sperm numbers per ejaculate or ejaculation frequency in response to female-related cues. We conclude that sequential male mate choice under sperm competition risk could be a widespread but often unappreciated mechanism of strategic sperm allocation.

Testing an Adaptationist Theory of Trait Covariation: Relative Bargaining Power as a Common Calibrator of an Interpersonal Syndrome

This article provides the first test of an adaptationist ‘common calibration’ theory to explain the origins of trait covariation, which holds that (i) personality traits are often facultatively calibrated in response to cues that ancestrally predicted the reproductive payoffs of different trait levels and (ii) distinct traits that are calibrated on the basis of common input cues will exhibit consistent patterns of covariation. This theory is applied to explain the covariation within a ‘personality syndrome’ encompassing various interpersonal trait dimensions (e.g. extraversion, emotionality and attachment styles). Specifically, it is hypothesized that these traits are inter–correlated because each is calibrated in response to relative bargaining power (RBP)—a joint function of one's ability to benefit others and harm others. Path analyses from a correlational study compellingly supported this theoretical model: Objective and self–perceived measures of RBP–enhancing phenotypic features (physical attractiveness and physical strength) influenced an internal regulatory variable indexing RBP (i.e. self–perceived RBP), which in turn had robust effects on each of the focal personality traits. Moreover, in support of the theory's core postulate, controlling for self–perceived RBP greatly reduced the covariation within the interpersonal syndrome. These novel findings illustrate the promise of an evolutionary psychological approach to elucidating trait covariation. Copyright © 2013 John Wiley & Sons, Ltd.

Telling Tales at Work

This article explores the adaptive functions of storytelling in the workplace from an evolutionary perspective. Based on the analysis of ethnographic studies on hunter-gatherer and modern work organizations, this article claims that storytelling, as an adapted cognitive device, was selectively retained by natural and sexual selection, because of its survival and reproductive payoff. The narrative production through storytelling is a natural coping mechanism and has been functional in both old and new ways of working life under different ecological conditions. This article also highlights underlying adapted psychological mechanisms of storytelling and discusses some evolutionarily informed practical implications and pedagogical applications.

Strategic male mate choice minimizes ejaculate consumption

Reproduction can be costly for males, particularly when they provide nutrient-rich ejaculates in the form of spermatophores or secondary ejaculatory components. These costs may further increase if females reject or consume a male’s ejaculate rather than using it for egg fertilization. Males should, therefore, attempt to minimize these costs to maximize their reproductive payoffs. We examined male reproductive investment toward virgin females in the Southern Bottletail Squid, Sepiadarium austrinum. Specifically, we assessed whether the presence of unfertilized eggs inside females influenced male reproductive investment, whether females removed spermatophores postcopulation, and what phenotypic characteristics influenced spermatophore removal. We found that males were more likely to attempt mating with females that were proportionally larger, but mated for longer and were more likely to transfer spermatophores to egg-carrying females. Females consistently ate spermatophores transferred by males, with the smallest females eating the most. However, males did not vary spermatophore investment according to female size or the associated risk of spermatophore consumption.

Telling Tales at Work: An Evolutionary Psychological Explanation

This paper explores the adaptive functions of storytelling in the workplace from an evolutionary psychological perspective. Based on the analysis of ethnographic studies on hunter-gatherer and modern work organizations, this paper claims that storytelling, as an adapted cognitive device, was selectively retained by natural and sexual selection, due to its survival and reproductive payoff. The narrative production through storytelling is a natural coping mechanism and has been functional in both old and new ways of working life under different ecological conditions. This paper also discusses some evolutionarily-informed practical implications of storytelling in contemporary organizations.

The Origins of Extraversion: Joint Effects of Facultative Calibration and Genetic Polymorphism

The origins of variation in extraversion are largely mysterious. Recent theories and some findings suggest that personality variation can be orchestrated by specific genetic polymorphisms. Few studies, however, have examined an alternative hypothesis that personality traits are facultatively calibrated to variations in other phenotypic features, and none have considered how these distinct processes may interact in personality determination. Since physical strength and physical attractiveness likely predicted the reproductive payoffs of extraverted behavioral strategies over most of human history, it was theorized that extraversion is calibrated to variation in these characteristics. Confirming these predicted patterns, strength and attractiveness together explained a surprisingly large fraction of variance in extraversion across two studies--effects that were independent of variance explained by an androgen receptor gene polymorphism. These novel findings initially support an integrative model wherein facultative calibration and specific genetic polymorphisms operate in concert to determine personality variation.

Displaying in the dark: light-dependent alternative mating tactics in the Alpine newt

Environment plays a major role for determining the kind of courtship behaviours or alternative mating tactics employed, but the effect of physical variables on fitness has received little attention. The Alpine newt courts during both day and night times and exhibits a complex suite of behaviours involving olfactory, visual and tactile cues. Displaying in both dark and light conditions may increase the number of mating opportunities and alleviate predation risk, but the frequency and efficacy of the various tactics deployed may vary across light conditions, leading males to vary their use of these tactics across different light regimes. To test this hypothesis, we video-recorded sexual encounters at two light intensities in a controlled experimental design. When courting in the dark, males used comparatively more olfactory rather than visual displays. They also relied more on positive feedback from the female before releasing a spermatophore for her to pick up. The particular mix of tactics used under each light condition is likely to be adaptive because in the dark (1) visual communication is hampered, making olfactory displays possibly more effective and (2) males depositing spermatophores are more likely to lose fertilizations to competitors. Mating in light and dark conditions has similar reproductive payoffs, which shows that displaying in the dark is not detrimental and may even be advantageous if predation risk is reduced at night. These results confirm the importance of taking into account physical variables to understand the evolution of sexual communication in animals.

A pigheaded compromise: do competition and predation explain variation in warthog group size?

The reproductive payoff to an individual for participating in a group will often be affected by the size of the group. Competition for resources and predation pressure are 2 primary factors that influence sociality and group size in a variety of species. In this correlative study, I investigated how resource competition and predation influenced group size and female reproduction in the common warthog, Phacochoerus africanus. The distribution of group sizes indicated that group size depended on the age and sex of the participants. Yearlings formed larger groups than adults, whereas adult males and adult females formed similar sized groups, although males were more likely to be solitary. The demand for preferred habitat, clan density, predation pressure, and the time of year explained significant variation in the size of adult female groups but not in the size of adult male or yearling groups. Clan areas with more warthogs per area of preferred habitat were associated with smaller adult female groups, whereas higher densities of warthogs were associated with larger group sizes. Increasing indication of predator presence in a clan area had little influence on grouping behavior in general but resulted in larger female group sizes late in the dry season and with increased sightings of females with juveniles. The relationship between group size and predation pressure may be a consequence of group stability and higher mortality in larger groups. Key words: common warthog, competition, group living, group size, Phacochoerus africanus, predation pressure, sociality. [Behav Ecol]

Origins of learned reciprocity in solitary ciliates searching grouped ‘courting’ assurances at quantum efficiencies

Learning to reciprocate socially valued actions, such as cheating and cooperation, marks evolutionary advances in animal intelligence thought unequalled by even colonial microbes known to secure respective individual or group fitness tradeoffs through genetic and epigenetic processes. However, solitary ciliates, unique among microbes for their emulation of simple Hebbian-like learning contingent upon feedback between behavioral output and vibration-activated mechanosensitive Ca 2+ channels, might be the best candidates to learn to reciprocate necessary preconjugant touches perceived during complex ‘courtship rituals’. Testing this hypothesis here with mock social trials involving an ambiguous vibration source, the large heterotrich ciliate Spirostomum ambiguum showed it can indeed learn to modify emitted signals about mating fitness to encourage paired reproduction. Ciliates, improving their signaling expertise with each felt vibration, grouped serial escape strategies gesturing opposite ‘courting’ assurances of playing ‘harder to get’ or ‘easier to get’ into separate, topologically invariant computational networks. Stored strategies formed patterns of action or heuristics with which ciliates performed fast, quantum-like distributed modular searches to guide future replies of specific fitness content. Heuristic-guided searches helped initial inferior repliers, ciliates with high initial reproductive costs, learn to sensitize their behavioral output and opportunistically compete with presumptive mating ‘rivals’ advertising higher quality fitness. Whereas, initial superior repliers, ciliates with low initial reproductive costs, learned with the aid of heuristics to habituate their behavioral output and sacrifice net reproductive payoffs to cooperate with presumptive ‘suitors’, a kind of learned altruism only before attributed to animal social intelligences. The present findings confirm that ciliates are highly competent decision makers capable of achieving paired fitness goals through learning.

A Consilient Canon? Bridges to and from Evolutionary Literary Analysis

Jonathan Gottschali and David Sloan Wilson, eds. The Literary Animal: Evolution and the Nature of Narrative. Evanston, Illinois: Northwestern University Press, zoos. PP. xxvi, 304. David P. Barash and Nanelle R. Barash, Madame Bovary's Ovaries: A Darwinian Look at Literature. New York: Delacorte Press, 2005. pp. 262. IN HIS FOREWORD TO The Literary Animal: Evolution and the Nature of Narrative, a new collection of twelve original essays promoting the claims of evolutionary literary analysis, the eminent biologist E. O. Wilson imagines that we are poised on the brink of one of the great events of intellectual history. Science and the humanities united! (vii). The proposed unification will not, however, command easy assent in English and literary studies. For literary studies will be expected discard many of the intellectual paradigms with which it has worked in the last thirty or so years. These paradigms--Marxist, feminist, psychoanalytic, and deconstructionist--so the argument of The Literary Animal runs, are derived from a constructionist hypothesis which has been disproved by neo-Darwinist philosophers and scientists, most prominently E. O. Wilson, Daniel C. Dennett, Steven Pinker, and Richard Dawkins. Diverting us away from the blank slate theory of mind, David Sloan Wilson, Jonathan Gottschall, and their fellow contributors propose put us in touch with the biological baseline that drives human nature and the literary representations drafted in its name. This will be the basis for literature's new consilience with science. Consilience, the title of Wilson's 1998 book on the unity of knowledge, is a word which looms large in The Literary Animal's articulation of its rationale. And it is a rationale that has caught the ear of the international media. As Gowan Dawson has recently pointed out, The Literary Animal has been the subject of articles in The New York Times (November 2005), The Guardian (November 2005), Nature (January 2006), and Science (February 2006) (Dawson, 308). The simultaneous publication of David and Nanelle Barahhes Madame Bovary's Ovaries: A Darwinian Look at Literature thus begins look like another step in a movement gain control of the literary field, wresting it from its social constructivist defenders. Wilson sees the prime actors in this movement as embattled, even scorned by tenured constructivists (Gottschall and Sloan Wilson, viii); Frederic Crews, a long-time critic of theory and a defender of empirical methods, sees the advent of evolutionary literary analysis as an opportunity to reclaim governance of the field--its appointments and promotions, its curricula, its standards for publication, its manner of debate--from the fast-talking superstars who have prostituted it crank theory, political conformism and cliquishness (xv). The Barashes (father and daughter collaborators) acknowledge the work of the embattled few, naming Brian Boyd, Jonathan Gottschall, Joseph Carroll, Robin Fox, and Michelle Sugiyama, all of whom are contributors The Literary Animal. For the Barashes, these writers direct their efforts at a technical audience (13), while their own book aims address, as their title intimates, a popular readership. E. O. Wilson--who appears be everywhere--provides a jacket comment hailing this important new development in literary criticism and praising its very readable prose style. This is the Barashes on Anna Karenina and Madame Bovary: Anna and Vronsky know perfectly well they want have sex. But it's the evolutionary logic behind it--the reproductive payoff and ultimate motivating force--that operates not only below the belt but also below the level of conscious awareness. By the same token, it is worth noting that Emma Bovary and her beaux--the wealthy rake Rodolphe and the attractive law student Leon--seemed no more eager reproduce . …

Sexual Conflict, Ecology, and Breeding Systems in Shorebirds

Evolutionary biologists strive to understand the immense variation in animals' breeding systems. Shorebirds represent an ideal model system for this endeavor, because they exhibit diverse breeding systems that include monogamy, with the parents cooperating to rear the young; and polygamy by the male, the female, or both parents, with one parent taking full responsibility for incubating the eggs and rearing the young. Recent experimental manipulations, mathematical models, and phylogenetic analyses reveal that evolutionary pressures may diverge as they act on mated pairs of shorebirds, favoring one parent at a cost to the other. We argue that different reproductive payoffs for the male and the female have had fundamental implications for the evolution of diverse breeding systems.

Male dwarf chameleons assess risk of courting large, aggressive females

Conflict between the sexes has traditionally been studied in terms of costs of mating to females and female resistance. However, courting can also be costly to males, especially when females are larger and aggressively resist copulation attempts. We examined male display intensity towards females in the Cape dwarf chameleon, Bradypodion pumilum, in which females are larger than males and very aggressive. We assessed whether aggressive female rejection imposes potential costs on males and whether males vary their display behaviour with intensity of female rejection, female size or relative size differences. Males persisted in courtship after initial female rejection in 84% of trials, and were bitten in 28% of trials. Attempted mounts were positively associated with males being bitten. Males reduced courtship with increased intensity of female rejection. Male courtship behaviour also varied with female size: males were more likely to court and approach smaller females, consistent with the hypothesis that larger females can inflict more damage. These results suggest that, in addition to assessing female willingness to mate, male dwarf chameleons may use courtship displays to assess potential costs of persistence, including costs associated with aggressive female rejection, weighed against potential reproductive pay-offs associated with forced copulation.