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Lunar cycles of reproduction in the clown anemonefish Amphiprion percula: individual-level strategies and population-level patternsSeymour, Jeremiah R. 23 April 2018 (has links)
Lunar cycles of reproduction are a widespread phenomenon in marine invertebrates and vertebrates. It is common practice to infer the adaptive value of this behavior based on the population level pattern. This practice may be flawed if individuals within the population are employing different reproductive strategies. Here, we capitalize on a long-term field study and a carefully controlled laboratory experiment of individually identifiable clown anemonefish, Amphiprion percula, to investigate the individual reproductive strategies underlying population-level patterns of reproduction. The field data reveal that A. percula exhibit a lunar cycle of reproduction at the population level. Further, the field data reveal that there is naturally occurring variation among individuals and within individuals in the number of times they reproduce per month. The laboratory experiment reveals that the number of times individuals reproduce per month is dependent on their food availability. Individuals are employing a conditional strategy, breeding once, twice or thrice per month, depending on resource availability. Breaking down the population level pattern by reproductive tactic, we show that each reproductive tactic has its own non-random lunar cycle of reproduction. Considering the adaptive value of these cycles, we suggest that all individuals, regardless of tactic, may avoid reproducing around the new moon. Further, individuals may avoid breeding in synchrony with each other, because of negative frequency dependent selection at the time of settlement. Most importantly, we conclude that determining what individuals are doing is a critical step toward understanding the adaptive value of lunar cycles of reproduction.
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Ensaios em história do pensamento econômico / Essays on the history of economic thoughtAndrada, Alexandre Flávio Silva 14 September 2012 (has links)
A presente tese de doutoramento é composta de três ensaios independentes (ainda que complementares) sobre a História do Pensamento Econômico, mais especificamente, da Macroeconomia. O primeiro ensaio - \"Uma Breve História sobre a Abordagem de Desequilíbrio na Macroeconomia\" - é uma versão revista e ampliada do artigo apresentado no XXXVIII Encontro Nacional de Economia da ANPEC em 2010 (Uma Breve História sobre a Abordagem de Desequilíbrio na Economia). Nossa argumentação vai de encontro às interpretações de Romer (1989) e Mankiw (2005) sobre a compreensão histórica daquele episódio, como também a hipótese levantada por Backhouse & Boianovsky (2005) sobre o fracasso da Macroeconomia do Desequilíbrio. O segundo ensaio se chama \"Uma Análise Histórica (e Retórica) do Discurso Doutrinário de Robert E. Lucas Jr.\". Se no primeiro ensaio argumentamos que parte do \"fracasso\" da Abordagem de Desequilíbrio deveu-se ao surgimento de um método entendido como superior pela maior parte dos economistas (o método de Lucas), neste investigamos o conteúdo daqueles artigos em que Lucas busca convencer os leitores da superioridade do seu método não a partir da comparação dos resultados obtidos por seu modelo em comparação a uma estrutura alternativa, mas sim com uma retórica polemista, fazendo uso de uma série de estratagemas retóricos. Nossa intenção é checar a validade de algumas de suas teses históricas e teóricas, bem como fazer um escrutínio dos expedientes retóricos utilizados pelo autor. O terceiro ensaio - \"Tese da Ancestralidade, Reinvenção da Tradição ou Superação Positiva? Uma Investigação sobre a \"Macroeconomia\" anterior a Keynes e as Causas do Sucesso da Teoria Geral\" - é derivada do segundo ensaio. Partimos da contraposição de hipóteses históricas de dois grandes autores da Macroeconomia sobre o estado da teoria \"macroeconômica\" anterior a Keynes, e as causas do sucesso da Teoria Geral. De um lado, Robert Lucas trata a Macroeconomia fundada por Keynes como um desvio na tradição equilibrista das análises de flutuação, cujo sucesso foi um \'feliz acidente histórico\', provocado principalmente por fatores alheios as vontades e até as simpatias de Keynes. De outro, Olivier Blanchard argumenta que o que havia antes de Keynes era uma grande diversidade de métodos e ausência de um aparato hegemônico, e o sucesso de Keynes deveu-se exclusivamente aos avanços teóricos e metodológicos apresentados naquela obra. / This PhD thesis contains three independent (although complementary) essays on the History of Economic Thought, more specifically on Macroeconomics History. The first essay - A Brief History of the Disequilibrium Approach in Macroeconomics - is a revised and expanded version of paper presented at the XXXVIII Meeting of ANPEC. Our argumentation challenges Romer (1989) and Mankiw (2005) interpretations about that episode. We also disagree (at some level) with Backhouse & Boianovsky (2005) hypothesis about the so-called \"failure\" of Non-Market-Clearing Approach. The second essay - A Historical (and Rhetorical) Analysis of Robert E. Lucas Junior\'s Doctrinaire Speech - is still a work in progress. If the first essay we argue that part of the \"failure\" of Disequilibrium Approach was due to the emergence of a method perceived as superior by most economists (lucasian method), here we investigate the content of those articles where Lucas seeks to persuade its readers of the superiority of his method not from the scrutiny of the results obtained by a specific model in comparison to an alternative structure, but mainly through a polemicist rhetoric. Our intention is to check the validity of some of its historical and theoretical arguments, and make a scrutiny of rhetorical expedients used by the author. The third essay - Ancestry Thesis, Reinvention of a Tradition or Cumulative Progress? A Research on \"Macroeconomics\" before Keynes and some Speculation about the causes of General Theory\'s Success\" - is derived from the second paper. We start from the juxtaposition of historical hypotheses of two great authors about the state\'s theory of \"macroeconomic\" before Keynes, and the causes of the success of the General Theory. On one hand, Robert Lucas argues that Macroeconomics as developed by Keynes was a deviation in the tradition of equilibrist fluctuation analysis, whose success was a fortunate historical accident. On the other, Olivier Blanchard argues that what was before Keynes was a great diversity of methods and the absence of a hegemonic apparatus, and the success of Keynes was due exclusively to theoretical and methodological advances made in that work.
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Ensaios em história do pensamento econômico / Essays on the history of economic thoughtAlexandre Flávio Silva Andrada 14 September 2012 (has links)
A presente tese de doutoramento é composta de três ensaios independentes (ainda que complementares) sobre a História do Pensamento Econômico, mais especificamente, da Macroeconomia. O primeiro ensaio - \"Uma Breve História sobre a Abordagem de Desequilíbrio na Macroeconomia\" - é uma versão revista e ampliada do artigo apresentado no XXXVIII Encontro Nacional de Economia da ANPEC em 2010 (Uma Breve História sobre a Abordagem de Desequilíbrio na Economia). Nossa argumentação vai de encontro às interpretações de Romer (1989) e Mankiw (2005) sobre a compreensão histórica daquele episódio, como também a hipótese levantada por Backhouse & Boianovsky (2005) sobre o fracasso da Macroeconomia do Desequilíbrio. O segundo ensaio se chama \"Uma Análise Histórica (e Retórica) do Discurso Doutrinário de Robert E. Lucas Jr.\". Se no primeiro ensaio argumentamos que parte do \"fracasso\" da Abordagem de Desequilíbrio deveu-se ao surgimento de um método entendido como superior pela maior parte dos economistas (o método de Lucas), neste investigamos o conteúdo daqueles artigos em que Lucas busca convencer os leitores da superioridade do seu método não a partir da comparação dos resultados obtidos por seu modelo em comparação a uma estrutura alternativa, mas sim com uma retórica polemista, fazendo uso de uma série de estratagemas retóricos. Nossa intenção é checar a validade de algumas de suas teses históricas e teóricas, bem como fazer um escrutínio dos expedientes retóricos utilizados pelo autor. O terceiro ensaio - \"Tese da Ancestralidade, Reinvenção da Tradição ou Superação Positiva? Uma Investigação sobre a \"Macroeconomia\" anterior a Keynes e as Causas do Sucesso da Teoria Geral\" - é derivada do segundo ensaio. Partimos da contraposição de hipóteses históricas de dois grandes autores da Macroeconomia sobre o estado da teoria \"macroeconômica\" anterior a Keynes, e as causas do sucesso da Teoria Geral. De um lado, Robert Lucas trata a Macroeconomia fundada por Keynes como um desvio na tradição equilibrista das análises de flutuação, cujo sucesso foi um \'feliz acidente histórico\', provocado principalmente por fatores alheios as vontades e até as simpatias de Keynes. De outro, Olivier Blanchard argumenta que o que havia antes de Keynes era uma grande diversidade de métodos e ausência de um aparato hegemônico, e o sucesso de Keynes deveu-se exclusivamente aos avanços teóricos e metodológicos apresentados naquela obra. / This PhD thesis contains three independent (although complementary) essays on the History of Economic Thought, more specifically on Macroeconomics History. The first essay - A Brief History of the Disequilibrium Approach in Macroeconomics - is a revised and expanded version of paper presented at the XXXVIII Meeting of ANPEC. Our argumentation challenges Romer (1989) and Mankiw (2005) interpretations about that episode. We also disagree (at some level) with Backhouse & Boianovsky (2005) hypothesis about the so-called \"failure\" of Non-Market-Clearing Approach. The second essay - A Historical (and Rhetorical) Analysis of Robert E. Lucas Junior\'s Doctrinaire Speech - is still a work in progress. If the first essay we argue that part of the \"failure\" of Disequilibrium Approach was due to the emergence of a method perceived as superior by most economists (lucasian method), here we investigate the content of those articles where Lucas seeks to persuade its readers of the superiority of his method not from the scrutiny of the results obtained by a specific model in comparison to an alternative structure, but mainly through a polemicist rhetoric. Our intention is to check the validity of some of its historical and theoretical arguments, and make a scrutiny of rhetorical expedients used by the author. The third essay - Ancestry Thesis, Reinvention of a Tradition or Cumulative Progress? A Research on \"Macroeconomics\" before Keynes and some Speculation about the causes of General Theory\'s Success\" - is derived from the second paper. We start from the juxtaposition of historical hypotheses of two great authors about the state\'s theory of \"macroeconomic\" before Keynes, and the causes of the success of the General Theory. On one hand, Robert Lucas argues that Macroeconomics as developed by Keynes was a deviation in the tradition of equilibrist fluctuation analysis, whose success was a fortunate historical accident. On the other, Olivier Blanchard argues that what was before Keynes was a great diversity of methods and the absence of a hegemonic apparatus, and the success of Keynes was due exclusively to theoretical and methodological advances made in that work.
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Explosions de cycles : analyses qualitatives, simulations numériques et modèles / Limits cycles explosions, qualitative analysis, numerical simulations and modelsMégret, Lucile 25 November 2016 (has links)
Ce travail porte sur de nouvelles explosions de cycles (orbites périodiques), l'étude de leur structure par l'analyse qualitative, leur mise en évidence par simulation numérique (Auto, Xpp) et la discussion de leur pertinence dans des modèles mathématiques dans les neurosciences. De telles explosions se produisent dans les systèmes dynamiques lents-rapides. La plupart des neurones sont excitables, dès 1940, Hodgkin identifia trois classes fondamentales d'axones excitables distinguées par leurs réponses à un courant injecté d'amplitude variable. A l'aide de la fonction de Lambert, nous étudions la transition entre les types I et II par des explosions de cycle incomplètes, initiées par une bifurcation de Hopf singulière et qui se terminent dans une bifurcation homocline dans des systèmes une variable rapide/une variable lente. Vient ensuite une étude poussée du système de Hindmarsh-Rose. Il s'agit d'un système deux variables rapides/une variable lente qui produit des oscillations en salves (ou bursting). Nous généralisons la notion d'ensembles candidats-limites-périodiques (clp) aux systèmes tridimensionnels, il s'agit des ensembles invariants du système à la limite singulière. A l'aide de ces derniers, nous obtenons une description très fine de la déformation du cycle limite jusqu'à l'addition d'un nouveau spike au burst. Nous finissons par une étude de la minimalité du modèle de F. Clément et J.-P. Françoise. Ce dernier est un système 4D qui modélise l¿activité des neurones à GnRH. Nous étudions un système une variable rapide/deux variables lentes qui reproduit certaines des caractéristiques du modèle 4D, notamment des Mixed-Modes oscillations. / This thesis is focussed on the analysis of novel explosions of limit cycles (periodic orbits). We provide a study of their structure by qualitative analysis, exhibit evidences of their existence by numerical simulations (Auto, Xpp) and propose a discussion of their relevance in mathematical modeling for neurosciences. Such explosions occur in the slow-fast dynamical systems. Most of neurons are excitable, Hodgkin (1940) identified three fundamental classes of excitable axon distinguished by their responses to a current of variable amplitude injected. Using the Lambert function, we study the transition between types I and II by incomplete explosion of cycle. This explosion, produced by a planar vector field with one fast/one slow variable, is initiated by a singular Hopf bifurcation and ends via a homoclinic bifurcation. The next chapter proposed a study of the Hindmarsh-Rose system. This system, composed of one fast/ two slow variables, is well known to produce square wave bursting oscillation. We generalize the notion of candidate-limit-perodic sets (CLP-sets) to three-dimensional systems. A CLP-set is an invariant set of the system in the singular limit. Using these, we get a very acurate description of the limit cycle deformation under the variation of a parameter until the addition of a new spike to burst. Finally, we propose a study fot the minimality of the model introduced by F. Clement and J.-P. Françoise. The latter is a 4D system that models the activity of GnRH neurons. We study a system composed by one fast /two slow variables that reproduces some of the features of the 4D model, including Mixed-Modes oscillations.
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