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Bshary, Redouan
Nom
Bshary, Redouan
Affiliation principale
Fonction
Professeur ordinaire
Email
redouan.bshary@unine.ch
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Résultat de la recherche
Voici les éléments 1 - 2 sur 2
- PublicationAccès libreAdjustments of levels of cooperation in cleaner wrasse "Labroides dimidiatus": the effects of an audience and satiation(2015)
Mon système modèle a consisté d’un mutualisme de nettoyage marin impliquant des labres nettoyeurs (Labroides dimidiatus) et ses poissons de récif dit «clients» qui leur rendent visite pour se faire enlever les ectoparasites. Cependant, des conflits surgissent car les nettoyeurs préfèrent la couche de mucus protectrice des clients aux ectoparasites, où se nourrir de mucus est préjudiciable au client et est donc fonctionnellement considéré comme de la tricherie. Par conséquent, les clients doivent faire en sorte que les nettoyeurs mangent contre leur préférence afin de pouvoir bénéficier d'un bon service de nettoyage. Des observations sur le terrain et une expérience de laboratoire utilisant des plaques en plexiglas en remplacement de clients avaient déjà suggéré que les clients spectateurs étaient attentifs à la manière dont un nettoyeur traite son client actuel et que les nettoyeurs sont plus coopératifs s’ils sont observés. J'ai pu démontrer ce concept de prestige social pour la première fois dans le cadre d'une expérience de laboratoire contrôlée utilisant de véritables interactions client-nettoyeur. Dans deux autres expériences utilisant soit des plaques en plexiglas soit de vrais clients, j'ai montré que les nettoyeurs peuvent ajuster la qualité de leurs services à l'importance relative du client actuel par rapport au client spectateur: plus le spectateur a de la valeur, plus le service envers le client actuel est peaufiné. Dans une troisième expérience, j’ai manipulé le niveau de satiété des nettoyeurs afin de tester la prédiction de la théorie du marché biologique selon laquelle un besoin d’interactions temporairement faible entraîne une baisse de la qualité du service. De manière quelque peu surprenante, cette prédiction n’a pas été confirmée, les nettoyeurs rassassiés ayant augmenté leur niveau de coopération envers leurs clients, c’est-à-dire qu’ils ont moins triché lors des interactions avec leurs clients et se sont nourris davantage contre leur préférence sur les plaques en plexiglas. Ainsi, les nettoyeurs rassassiés investissent fonctionnellement dans leur relation avec les clients pour des avantages futurs.
En conclusion, mon travail de recherche démontre que le labre nettoyeur L. dimidiatus, est capable de prendre des décisions sophistiquées, adaptées aux spécificités de la situation. Les résultats soulèvent des questions concernant les processus cognitifs sous-jacents, car ils remettent en cause la notion selon laquelle des cerveaux plus larges sont nécessaires pour une coopération sophistiquée. Au lieu de cela, il semble qu'une approche écologique par rapport à la cognition soit plus appropriée pour expliquer mes résultats. Mon étude s'inscrit dans une longue tradition selon laquelle les poissons constituent des systèmes modèles idéaux pour tester la théorie de la coopération, dont les résultats prometteurs devraient inspirer de nouvelles analyses théoriques., Cooperation, the mutual helping between unrelated individuals, is an evolutionary puzzle. This is because helping is often an investment that must yield future benefits in order to be under positive selection. Generally, natural selection favours individuals that perform self-serving behaviour, and hence cheating is a major conceptual issue. However, examples of cooperation are abundant in nature. As such, finding explanations that reconcile cooperation with evolutionary theory has long been a major focus in biology but also in the social sciences with their aim to explain the social complexity in humans. A variety of so-called partner control mechanisms – behavioural responses that cause a reduction in the payoffs of a cheating partner such that a cooperating partner gains more – have been shown to stabilise cooperation. My research has focused in particular on the role of social prestige in a communication network. Many animal interactions are observed by third parties (“bystanders”), who may gain valuable information about the interactants. In the context of cooperation, bystanders should try to identify particularly cooperative individuals as future partners, which selects for individuals being particularly cooperative if they are observed.
My model system has been marine cleaning mutualism involving bluestreak cleaner wrasses (Labroides dimidiatus) and their so-called “client” reef fishes that visit to have ectoparasites removed. However, conflict arises as cleaners prefer the protective mucus layer of clients over ectoparasites, where mucus feeding is detrimental to the client and hence functionally constitutes cheating. Thus, clients have to make cleaners feed against their preference in order to receive a good cleaning service. Field observations and a laboratory experiment using Plexiglas plates as client surrogates had already suggested that bystander clients pay attention to how a cleaner treats its current client, and that cleaners are more cooperative if observed. I could demonstrate this social prestige concept for the first time in a controlled laboratory experiment in real cleaner-client interactions. In two further experiments using either plates or real clients I showed that cleaners can fine-tune their service quality to the relative importance of current client versus bystander: the more valuable the bystander the better the current service. Finally, I manipulated the cleaners’ level of satiation in order to test the prediction from biological market theory that a temporarily low need for interactions causes a decrease in service quality. Somewhat surprisingly, this prediction was not met as satiated cleaners increased their cooperation levels towards their clients, i.e. they caused less jolts during interactions with their clients and fed more against their preference on plates. Thus, satiated cleaners functionally invest into their relationship with clients for future benefits.
In conclusion, my work shows that cleaner wrasse L. dimidiatus show sophisticated decision rules that are fine-tuned to the specifics of the situation. The results raise questions concerning the underlying cognitive processes as they challenge the notion that large brains are necessary for sophisticated cooperation. Instead, it appears that an ecological approach to cognition is better suited to explain my results. My study fits into a long tradition that fish yield ideal model systems to test cooperation theory, where results hopefully inspire further theoretical analyses. - PublicationAccès libreThe effect of nectar reduction in Petunia Axillaris on foraging behavior of noctural hawkmoths, observed in laboratory and field behavioral assays(2009)
; Kuhlemeier, CrisA key component shaping plant-pollinator interactions is nectar. Its volume can regulate the length and frequency of pollination events. Nectar provisioning can be costly for the plant. Once secreted by the nectaries, the sugar-rich solution is usually consumed by a floral visitor and lost for “recycling” within the plant. Nectar reduction should thus be advantageous for the plant: non-secreted carbohydrates can be reallocated within the plant to other structures promoting growth, reproduction or attraction. However, most angiosperms provide nectar. It is assumed that certain pollinator behaviors, so called partner control mechanisms, favor nectariferous over deceptive plants and ultimately prevent the spread of “cheaters”. The partner control mechanisms identified in the context of plant-pollinator mutualisms are avoidance of nectarless species, reduction of drinking time and number of flowers visited on nectarless plants. Not all behaviors are performed simultaneously, and external conditions such as plant density as well as intrinsic factors of the foraging insect can determine to which extent certain behaviors are exerted. In the present study, we analyze foraging behavior of nocturnal hawkmoths on cheating Petunia axillaris axillaris plants under several conditions. The aim of this thesis was to assess which partner control mechanisms are executed by pollinators facing nectarless/low nectar plants. We observed hawkmoth behavior in two field sites and conducted experiments with naïve and experienced hawkmoths Manduca sexta under controlled conditions. We investigated which of the foraging decision rules might potentially reduce the fitness of cheaters and thus limit their spread in a population. In field assays, we observed that the density of naturally occurring P. axillaris plants and the presence of alternative food sources can influence hawkmoth behavior on nectarless Petunias: only when food plants were abundant and dense, pollinators would reduce the number of flowers on nectarless Petunias, whereas in the lower density there seemed to be no selection against cheaters. In learning experiments under controlled conditions, we observed that none of the tested behaviors (reduction of drinking duration on nectarless plants, avoidance of nectarless plants, reduction of number of flowers visited on nectarless plants) were improved over the course of the experiment. However, in all learning trials there was a significant reduction of drinking duration on nectarless plants, indicating that this control mechanism of hawkmoths is always exerted innately. Learning might therefore not be of major importance in discrimination against cheaters in our system. We constructed a plant with extremely high phenotypic similarity to P. axillaris yet only a third of the regular nectar volume (F25). Genotyping of F25 revealed a high genotypic imilarity to its parental plant but failed to answer questions about the genetic background of low nectar volume. The low nectar line was used in behavioral experiments with Manduca sexta. A major goal was to find out how pollination behavior affects female reproductive success of F25. Analogous to previous experiments, we found that the drinking duration was significantly reduced on cheaters. In hand pollination assays, F25 produced significantly more seeds than P. axillaris, however this effect was neutralized when pollinated by Manduca sexta. The benefits of nectar reduction are thus counterbalanced by a change in pollinator foraging behavior. In the future, we would like to assess which other fitness parameters are concerned when a plant ceases its nectar production. Altogether, we were able to show which foraging rules are exerted by hawkmoths on cheating P. axillaris and how one partner control mechanism, namely drinking duration, affects seed set of a plant with reduced nectar offerings. We hope that this work has contributed to answering questions about the costs and benefits of cheating.