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Earley, R. L., Tinsley, M., & Dugatkin, L. A. (2003). To see or not to see: does previewing a future opponent affect the contest behavior of green swordtail males (Xiphophorus helleri)? Naturwissenschaften, 90(5), 226–230.
Abstract: Animals assess the fighting ability of conspecifics either by engaging in aggressive interactions or observing contests between others. However, whether individuals assess physical prowess outside the context of aggressive interactions remains unknown. We examined whether male green swordtails (Xiphophorus helleri) extract information about the fighting ability of solitary individuals via observation and whether acquiring such information elicits behavioral modifications. Contests preceded by mutual visual assessment were significantly shorter than fights where only one or neither of the two individuals was informed in advance. Focal animals initiated aggressive behavior more often against larger opponents only after previewing their adversary, indicating that swordtails can extract information about relative body size from watching solitary conspecifics. When a fighting disadvantage is perceived, observers adopt tactics that increase their probability of winning the contest.
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Dugatkin, L. A., & Bekoff, M. (2003). Play and the evolution of fairness: a game theory model. Behav. Process., 60(3), 209–214.
Abstract: Bekoff [J. Consci. Stud. 8 (2001) 81] argued that mammalian social play is a useful behavioral phenotype on which to concentrate in order to learn more about the evolution of fairness. Here, we build a game theoretical model designed to formalize some of the ideas laid out by Bekoff, and to examine whether `fair' strategies can in fact be evolutionarily stable. The models we present examine fairness at two different developmental stages during an individual's ontogeny, and hence we create four strategies--fair at time 1/fair at time 2, not fair at time 1/not fair at time 2, fair at time 1/not fair at time 2, not fair at time 1/fair at time 2. Our results suggest that when considering species where fairness can be expressed during two different developmental stages, acting fairly should be more common than never acting fairly. In addition, when no one strategy was evolutionarily stable, we found that all four strategies we model can coexist at evolutionary equilibrium. Even in the absence of an overwhelming database from which to test our model, the general predictions we make have significant implications for the evolution of fairness.
Keywords: Play; Fairness; Game theory
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Dugatkin, L. A., Mesterton-Gibbons, M., & Houston, A. I. (1992). Beyond the prisoner's dilemma: Toward models to discriminate among mechanisms of cooperation in nature. Trends Evol. Ecol., 7, 202–205.
Abstract: The iterated prisoner's dilemma game, or IPD, has now established itself as the orthodox paradigm for theoretical investigations of the evolution of cooperation; but its scope is restricted to reciprocity, which is only one of three categories of cooperation among unrelated individuals. Even within that category, a cooperative encounter has in general three phases, and the IPD has nothing to say about two of them. To distinguish among mechanisms of cooperation in nature, future theoretical work on the evolution of cooperation must distance itself from economics and develop games as a refinement of ethology's comparative approach.
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Dugatkin, L. A., & Godin, J. G. (1992). Reversal of female mate choice by copying in the guppy (Poecilia reticulata). Proc Biol Sci, 249(1325), 179–184.
Abstract: Ever since Fisher (1958) formalized models of sexual selection, female mate choice has been assumed to be a genetically determined trait. Females, however, may also use social cues to select mates. One such cue might be the mate choice of conspecifics. Here we report the first direct evidence that a female's preference for a particular male can in fact be reversed by social cues. In our experiments using the Trinidadian guppy (Poecilia reticulata), this reversal was mediated by mate-copying opportunities, such that a female (the 'focal' female) is given the opportunity to choose between two males, followed by a period in which she observes a second female (the 'model' female) displaying a preference for the male she herself did not prefer initially. When allowed to choose between the same males a second time, compared with control tests, a significant proportion of focal females reversed their mate choice and copied the preference of the model female. These results provide strong evidence for the role of non-genetic factors in sexual selection and underlie the need for new models of sexual selection that explicitly incorporate both genetic and cultural aspects of mate choice.
Keywords: Acclimatization; Animals; *Choice Behavior; Female; Male; Poecilia; *Sexual Behavior, Animal
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Dugatkin, L. A. (1991). Dynamics of the TIT FOR TAT strategy during predator inspection in the guppy (Poecilia reticulata). Behav. Ecol. Sociobiol., 29(2), 127–132.
Abstract: One well-known solution to the iterated Prisoner's Dilemma is the TIT FOR TAT strategy. This strategy has three “characteristics” associated with it. TIT FOR TAT is nice (cooperates on the first move of a game), retaliatory (plays defect against an individual that defected on the prior move), and forgiving (cooperates with an individual which has defected in the past but cooperates in the present). Predator inspection behavior in guppies (Poecilia reticulata) was examined in order to determine whether guppies displayed these three characteristics. Results indicate that while it can be quite difficult to translate the abstract concepts of niceness, retaliation, and forgiveness into measurable behaviors, the data support the hypothesis that guppies display the three characteristics associated with the TIT FOR TAT strategy.
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Dugatkin, L. A. (1992). Tendency to inspect predators predicts mortality risk in the guppy (Poecilia reticulata). Behav. Ecol., 3(2), 124–127.
Abstract: Although predator inspection behavior in fishes has become a model system for examining game theoretical strategies such as Tit for Tat, the direct costs of inspection behavior have not been quantified. To begin quantifying such costs, I conducted an experiment that examined mortality due to predation as a function of predator inspection in the guppy (Poecilia reticulata). Before being subjected to a “survivorship” experiment, guppies were assayed for their tendency to inspect a predator. Groups were then composed of six guppies that differed in their tendency to inspect. These groups were placed into a pool containing a predator, and survivorship of guppies with different inspection tendencies was noted 36 and 60 h later. Results indicate that individuals that display high degrees of inspection behavior suffer greater mortality than their noninspecting shoalmates.
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Dugatkin, L. A., Perlin, M., & Atlas, R. (2003). The Evolution of Group-beneficial Traits in the Absence of Between-group Selection. J. Theor. Biol., 220(1), 67–74.
Abstract: One specific prediction emerging from trait-group models of natural selection is that when individuals possess traits that benefit other group members, natural selection will favor “cheating” (i.e. not possessing the group-beneficial trait) within groups. Cheating is selected within groups because it allows individuals to avoid bearing the relative costs typically associated with group-beneficial traits, but to still reap the benefits associated with the acts of other group members. Selection between groups favors traits that benefit other group members. The relative strength of within- and between-group selection then determines the equilibrium frequency of those who produce group-beneficial traits and those that do not. Here we demonstrate that individual-level selection, that is selection within groups can also produce an intermediate frequency of such group-beneficial traits by frequency-dependent selection. The models we develop are general in nature, but were inspired by the evolution of antibiotic resistance in bacteria. The theory developed here is distinct from prior work that relies on reciprocity or kinship per'se to achieve cooperation and altruism among group members.
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Crowley, P. H., Provencher, L., Sloane, S., Dugatkin, L. A., Spohn, B., Rogers, L., et al. (1996). Evolving cooperation: the role of individual recognition. Biosystems, 37(1-2), 49–66.
Abstract: To evaluate the role of individual recognition in the evolution of cooperation, we formulated and analyzed a genetic algorithm model (EvCo) for playing the Iterated Prisoner's Dilemma (IPD) game. Strategies compete against each other during each generation, and successful strategies contribute more of their attributes to the next generation. Each strategy is encoded on a `chromosome' that plays the IPD, responding to the sequences of most recent responses by the interacting individuals (chromosomes). The analysis reported in this paper considered different memory capabilities (one to five previous interactions), pairing continuities (pairs of individuals remain together for about one, two, five, or 1000 consecutive interactions), and types of individual recognition (recognition capability was maximal, nil, or allowed to evolve between these limits). Analysis of the results focused on the frequency of mutual cooperation in pairwise interactions (a good indicator of overall success in the IPD) and on the extent to which previous responses by the focal individual and its partner were associated with the partner's identity (individual recognition). Results indicated that a fixed, substantial amount of individual recognition could maintain high levels of mutual cooperation even at low pairing continuities, and a significant but limited capability for individual recognition evolved under selection. Recognition generally increased mutual cooperation more when the recent responses of individuals other than the current partner were ignored. Titrating recognition memory under selection using a fitness cost suggested that memory of the partner's previous responses was more valuable than memory of the focal's previous responses. The dynamics produced to date by EvCo are a step toward understanding the evolution of social networks, for which additional benefits associated with group interactions must be incorporated.
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Dugatkin, L. A., & Mesterton-Gibbons, M. (1996). Cooperation among unrelated individuals: reciprocal altruism, by-product mutualism and group selection in fishes. Biosystems, 37(1-2), 19–30.
Abstract: Cooperation among unrelated individuals can evolve not only via reciprocal altruism but also via trait-group selection or by-product mutualism (or some combination of all three categories). Therefore the (iterated) prisoner's dilemma is an insufficient paradigm for studying the evolution of cooperation. We replace this game by the cooperator's dilemma, which is more versatile because it enables all three categories of cooperative behavior to be examined within the framework of a single theory. Controlled studies of cooperation among fish provide examples of each category of cooperation. Specifically, we describe reciprocal altruism among simultaneous hermaphrodites that swap egg parcels, group-selected cooperation among fish that inspect dangerous predators and by-product mutualism in the cooperative foraging of coral-reef fish.
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Johnstone, R. A., & Dugatkin, L. A. (2000). Coalition formation in animals and the nature of winner and loser effects. Proc. Roy. Soc. Lond. B Biol. Sci., 267(1438), 17–21.
Abstract: Coalition formation has been documented in a diverse array of taxa, yet there has been little formal analysis of polyadic interactions such as coalitions. Here, we develop an optimality model which examines the role of winner and loser effects in shaping coalition formation. We demonstrate that the predicted patterns of alliances are strongly dependent on the way in which winner and loser effects change with contestant strength. When winner and loser effects decrease with the resource-holding power (RHP) of the combatants, coalitions will be favoured between the strongest members of a group, but not between the weakest. If, in contrast, winner and loser effects increase with RHP, exactly the opposite predictions emerge. All other things being equal, intervention is more likely to prove worthwhile when the beneficiary of the aid is weaker (and its opponent is stronger), because the beneficiary is then less likely to win without help. Consequently, intervention is more probable when the impact of victory on the subsequent performance of a combatant increases with that individual's strength because this selects for intervention in favour of weaker combatants. The published literature on hierarchy formation does not reveal how winner and loser effects actually change with contestant strength and we therefore hope that our model will spur others to collect such data; in this light we suggest an experiment which will help to elucidate the nature of winner and loser effects and their impact on coalition formation in animals.
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