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Bshary, Redouan
Nom
Bshary, Redouan
Affiliation principale
Fonction
Professeur ordinaire
Email
redouan.bshary@unine.ch
Identifiants
Résultat de la recherche
Voici les éléments 1 - 6 sur 6
- PublicationMétadonnées seulementEndogenous oxytocin predicts helping and conversation as a function of group membership(2018-7-4)
; ; ; ; Humans cooperate with unrelated individuals to an extent that far outstrips any other species. We also display extreme variation in decisions about whether to cooperate or not, and the mechanisms driving this variation remain an open question across the behavioural sciences. One candidate mechanism underlying this variation in cooperation is the evolutionary ancient neurohormone oxytocin (OT). As current research focuses on artificial administration of OT in asocial tasks, little is known about how the hormone in its naturally occurring state actually impacts behaviour in social interactions. Using a new optimal foraging paradigm, the ‘egg hunt’, we assessed the association of endogenous OT with helping behaviour and conversation. We manipulated players' group membership relative to each other prior to an egg hunt, during which they had repeated opportunities to spontaneously help each other. Results show that endogenous baseline OT predicted helping and conversation type, but crucially as a function of group membership. Higher baseline OT predicted increased helping but only between in-group players, as well as decreased discussion about individuals’ goals between in-group players but conversely more of such discussion between out-group players. Subsequently, behaviour but not conversation during the hunt predicted change in OT, in that out-group members who did not help showed a decrease in OT from baseline levels. In sum, endogenous OT predicts helping behaviour and conversation, importantly as a function of group membership, and this effect occurs in parallel to uniquely human cognitive processes. - PublicationAccès libreWhat makes a cleaner a cleaner ?(2016)
; In his last presidential address to the Royal Society in 2005, Robert M. May stated that “The most important unanswered question in evolutionary biology, and more generally in the social sciences, is how cooperative behaviour evolved and can be maintained”. My thesis provides a contribution to answering this big question by investigating how one particular species evolved for an ecology that rests heavily upon cooperative interactions: the bluestreak cleaner wrasse Labroides dimidiatus. This species engages in up to 2000 cooperative interactions per day with dozens of other ‘client’ coral reef fishes, thus making it a prime system for studying cooperation between unrelated individuals. Conflicts between cleaners and clients arise because the former prefer to bite clients to eat their protective mucus rather than focusing on ectoparasites. In response to such exploitation, clients use various forms of partner control mechanisms that promote cooperative behaviour in cleaners. As a result, cleaners are known to use a diversity of strategic behaviours to determine when to cheat and when to cooperate. Cleaners’ behaviour thus appears very well adapted to the demands of their peculiar ecology.
In my thesis, I used a comparative approach to investigate which traits appear to be associated with the highly social ecology of cleaners, or in other words: What makes a cleaner a cleaner? Through a series of experiments, I compared the cognitive skills, escape performance, foraging ecology and vision of L. dimidiatus with other species of labrids that do not engage in cleaning (or only occasionally). These comparisons allowed me to identify some of the characteristics that set cleaners apart, and thus further our understanding of how social ecology can affect the evolution of a species.
In the first chapter, I showed that L. dimidiatus was able to fine-tune its level of cooperation to the specifics of different cleaning-related situations, an ability that was absent in the closely related Halichoeres melanurus. In the second chapter, I investigated whether the demands of a highly social lifestyle led to an overall increase of cognitive performance in L. dimidiatus, or whether performance was tightly linked to ecological demands. L. dimidiatus outperformed five other species of labrids in two ecologically relevant tasks. However, all species performed similarly in a task with little ecological relevance, suggesting that cognition in cleaners is tightly linked to the challenges faced in nature. In the third chapter, results from foraging experiments suggest that L. dimidiatus evolved a foraging position that allows for increased efficiency in cleaning interactions. In comparison with four other species, L. dimidiatus adopted a significantly lower body angle with regards to the substrate when foraging. Furthermore, this species experienced almost no reduction in efficiency when searching for cryptic food items in comparison with conspicuous ones, while the other species all performed worse in the cryptic condition. It thus appears that the peculiar foraging posture of L. dimidiatus is well suited for cleaning interactions. Unfortunately, my current data did not allow assessing whether the visual system also adapted for a low body angle while foraging. Finally, in the last chapter, I asked whether because of the service they provide to predators, a reduction in predation pressures led to the decay of escape performance in L. dimidiatus. Interestingly, measures of escape performance in a controlled laboratory setup showed that L. dimidiatus was among the top performers in comparison with 5 other labrids. These results suggest that the risks associated with cleaning interactions are sufficient to maintain a high escape performance in cleaners, despite their privileged relationship with predatory clients.
In summary, a wide range of characteristics appear to be important for cleaning interactions, and species that specialized in this activity seem to have undergone very different selective pressures than fishes with more standard ecologies. Identifying some of the key aspects related to the ecology of cleaners provides a good example of how the evolution of a species can be affected by the demands of a highly social life. In this system, I argue that competition among service providers and conflicts of interests between cleaners and clients appear to be the major drivers of adaptation. - PublicationAccès libreEvolution of spite through indirect reciprocity(2003-11-07)
- PublicationAccès libreCleaner wrasse prefer client mucus : support for partner control mechanisms in cleaning interactions(2003-11-07)
- PublicationAccès libreBuilding up relationships in asymmetric co-operation games between the cleaner wrasse Labroides dimidiatus and client reef fish(2002)It has been suggested that individuals may prevent partners from cheating by building up relationships slowly, giving very little in the beginning and raising the stakes in subsequent moves if partners reciprocate. I tested this idea with field experiments on the cleaner-fish Labroides dimidiatus and its "client" reef fish. Clients visit cleaners at their small territories, so-called cleaning stations, to have parasites removed. Cleaners were first observed and then caught and either put back on their original territory or moved to a new site. I noted a variety of cleaner and client behaviour to evaluate how, if at all, relationships are built up. Cleaners and resident clients indeed build up relationships, but with heavy initial investment. There was no evidence that cleaners build up relationships with client species that have access to several cleaners. Finally, it appeared that cleaners constantly invest in relationships with predatory clients, possibly to reduce the risk that predators try to catch them. I propose that asymmetries between partners with respect to either payoff values or strategic options are the major reason why the results do not fit the so-called raising-the-stakes strategy.
- PublicationAccès libreCleaner fish Labroides dimidiatus manipulate client reef fish by providing tactile stimulation(2001-07-22)
; Würth, Manuela WürthThe cleaner wrasse Labroides dimidiatus often touches 'client' reef fish dorsal fin areas with its pelvic and pectoral fins. The relative spatial positions of cleaner and client remain constant and the cleaner's head points away from the client's body. Therefore, this behaviour is not compatible with foraging and the removal of client ectoparasites. As clients seek such 'tactile stimulation', it can be classified as an interspecific socio-positive behaviour. Our field observations on 12 cleaners (observation time of 112h) suggest that cleaners use tactile stimulation in order to successfully (i) alter client decisions over how long to stay for an inspection, and (ii) stop clients from fleeing or aggressive chasing of the cleaner in response to a cleaner fish bite that made them jolt. Finally, predatory clients receive tactile stimulation more often than non-predatory clients, which might be interpreted as an extra service that cleaners give to specific partners as pre-conflict management, as these partners would be particularly dangerous if they started a conflict. We therefore propose that cleaner fish use interspecific social strategies, which have so far been reported only from mammals, particularly primates.