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Caractérisation de la plasticité transgénérationnelle : le cas des défenses contre les prédateurs du gastéropode Physa acuta
No full textThe environment is variable in space and time. How organisms adapt to their environment is a hot topic in evolutionary biology, particularly in the current context of global change where human activities generate rapid environmental variations. Transgenerational plasticity (TGP hereafter) may represent an important process for organisms to adapt to a variable environment and has therefore been highly studied since its first description about twenty years ago. TGP extends the concept of phenotypic plasticity across generations and occurs when the environment of the parents, or more distant ancestors, influences offspring phenotype without altering the offspring DNA sequence. TGP could be particularly important in predator-prey interactions which affect virtually all animals. Indeed, it has been shown that offspring can produce defences in response to the detection of predator presence by the parents. TGP then allows offspring to be pre-adapted to predator presence in their environment. In this thesis, we aim to better understand predator-induced TGP in animals by characterising several factors that could influence it. We first realize a comprehensive review on all papers published on this subject. Then, through successive experiments, we characterise several factors altering TGP of defences using the small freshwater snail Physa acuta as a model. The main results are: 1. TGP is not restricted to parental environment: morphological and behavioural defences are influenced by the presence of predator cues in the environment of mothers, fathers and grandparents; 2. TGP is strongly "trait-dependent": exposure to predator cues has different transgenerational effects depending on the defences measured; 3. A large number of factors determines the presence of transgenerational effects on offspring defences: the offspring environment, the sex of the parent exposed to predator cues, the generation exposed (parental or grandparental generation) and the timing of the parents' exposure to predator cues during their development; 4. TGP influences group mean of behavioural defences (i.e. mean behaviour over several individuals), but no transgenerational effect on between-individual variance in behaviour was highlighted (animal personality); 5. The adaptive nature of TGP remains equivocal. Depending on experiences and defences, parental exposure to predator cues induced the expression of offspring defences and thus pre-adapted offspring to predator presence, or conversely decreased the expression of offspring defences. TGP therefore plays a role in the expression of predator-induced defences. This thesis shows that TGP depends on multiple factors that can interact with each other: the trait considered, the offspring environment, the parent exposed to predator cues (mother, father, or grandparent) and the timing of exposure to predator cues. Thus, by identifying key factors for TGP of defences against predators, this thesis highlights many research perspectives that will ultimately lead to a more global and integrative understanding of the causes and consequences of TGP.Les êtres vivants vivent dans un environnement variable dans le temps et dans l’espace. La manière dont les êtres vivants s'adaptent à leur environnement est une question fondamentale en biologie évolutive, notamment dans le contexte actuel où les activités humaines génèrent des variations rapides de l’environnement. La plasticité transgénérationnelle (abrégée TGP ci-après) pourrait être un processus important dans l’adaptation des organismes à un environnement variable et suscite donc l’intérêt de la communauté scientifique depuis sa première description formelle il y a une vingtaine d’années. La TGP est l’extension au travers des générations de la plasticité phénotypique et se manifeste lorsque l’environnement des parents, ou ancêtres plus lointains, influence le phénotype des descendants, sans passer par une modification de l’ADN des descendants. La TGP pourrait notamment être un processus important dans les interactions prédateur-proie qui concernent la majorité des animaux. En effet, il a été montré que les descendants peuvent produire des défenses en réponse à la détection d’indices (de la présence) de prédateurs par les parents. Ainsi, la TGP permet une préadaptation des descendants à la présence de prédateurs dans leur environnement. L’objectif de cette thèse est d’améliorer la compréhension de la TGP des défenses contre les prédateurs chez les animaux en caractérisant plusieurs facteurs susceptibles de l’influencer. Le premier objectif de cette thèse était de réaliser une synthèse bibliographique sur ce sujet. Ensuite, à travers une succession d’expériences, nous avons caractérisé plusieurs facteurs impactant la TGP des défenses en prenant comme modèle biologique un petit gastéropode d’eau douce, la physe aiguë (Physa acuta). Les résultats principaux sont que : 1. la TGP des défenses n’est pas restreinte à l’environnement parental : les défenses morphologiques et comportementales sont influencées par la présence d’indices de prédateurs dans l'environnement des mères, des pères et des grands-parents ; 2. la TGP est fortement “trait-dépendante” : les effets transgénérationnels de l’exposition à des indices de prédateurs étaient différents entre les différentes défenses mesurées ; 3. la présence d’effets transgénérationnels sur les défenses des descendants dépend d’un grand nombre de facteurs : l’environnement des descendants, le sexe du parent exposé aux indices de prédateurs, de la génération exposée (génération parentale ou grand-parentale) et du moment de l’exposition des parents aux indices de prédateurs pendant leur développement ; 4. la TGP impacte les défenses comportementales à l'échelle moyenne (moyenne phénotypique sur plusieurs descendants), mais aucun effet transgénérationnel sur la variance comportementale entre les descendants n’a été trouvé (personnalité animale) ; 5. la nature adaptative de la TGP reste équivoque. En fonction des expériences et des défenses, l’exposition parentale aux indices de prédateurs a induit l’expression des défenses chez les descendants et a donc pré-adapté les descendants à la présence de prédateurs, ou à l’inverse a diminué l'expression des défenses des descendants. La TGP joue donc un rôle dans l’expression des défenses contre les prédateurs. Ce travail de thèse démontre que la TGP dépend de multiples facteurs qui peuvent interagir entre eux : le trait considéré, l’environnement des descendants, le parent exposé aux indices de prédateurs (mère, père ou grand-parent) et le moment de l’exposition aux indices de prédateurs. Ainsi, en identifiant des facteurs clés de la TGP des défenses contre les prédateurs, ce travail de thèse met en lumière de nombreuses pistes de recherche qui ultimement permettront une compréhension plus globale et intégrative des causes et conséquences de la TGP
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Offspring reaction norms shaped by parental environment: interaction between within- and trans-generational plasticity of inducible defenses
No full textInternational audienceBackground: Within-generational plasticity (WGP) and transgenerational plasticity (TGP) are mechanisms allowing rapid adaptive responses to fluctuating environments without genetic change. These forms of plasticity have often been viewed as independent processes. Recent evidence suggests that WGP is altered by the environmental conditions experienced by previous generations (i.e., TGP). In the context of inducible defenses, one of the most studied cases of plasticity, the WGP x TGP interaction has been poorly investigated.Results: We provide evidence that TGP can alter the reaction norms of inducible defenses in a freshwater snail. The WGP x TGP interaction patterns are trait-specific and lead to decreased slope of reaction norms (behaviour and shell thickness). Offspring from induced parents showed a higher predator avoidance behaviour and a thicker shell than snails from non-induced parents in no predator-cue environment while they reached similar defenses in predator-cue environment. The WGP x TGP interaction further lead to a switch from a plastic towards a constitutive expression of defenses for shell dimensions (flat reaction norm).Conclusions: WGP-alteration by TGP may shape the adaptive responses to environmental change and then has a substantial importance to understand the evolution of plasticity
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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