Pour comprendre comment la sélection naturelle modèle les traits sexuels, l’emploi d’une approche intégrative des processus sélectifs en jeu semble aujourd’hui indispensable. Durant ma thèse je me suis ainsi intéressé aux influences simultanées des sélections de viabilité et sexuelle sur l’origine, l’évolution et le maintien des traits sexuels de la petite teigne de la ruche (Achroia grisella). Chez cette pyrale les mâles se regroupent en leks, produisent un chant d’appel ultrasonique intense et les femelles choisissent un partenaire sexuel en se basant sur des caractéristiques acoustiques spécifiques de ce chant. Cependant les signaux sexuels ultrasoniques des mâles peuvent également attirer des prédateurs : les chauves-souris insectivores. Ainsi, au sein des leks, les sélections sexuelle et de viabilité jouent et peuvent modeler (1) l’évolution du choix des femelles, (2) le maintien et l’évolution du lek, (3) l’origine de la communication acoustique sexuelle. Les travaux conduits durant cette thèse soulignent l’intérêt de l’étude du jeu des sélections sexuelle et de viabilité pour comprendre comment la sélection naturelle peut modeler l’origine, l’évolution et le maintien des traits sexuels. Les résultats indiquent en particulier le rôle crucial de la pression de prédation dans ces processus sélectifs. / In order to achieve a better understanding of how natural selection shapes sexual traits it is essential to consider the interplay of the various selective processes at work. For my thesis I investigated the simultaneous influences of viability and sexual selections on the origin, the evolution and the maintenance of sexual traits in the lesser waxmoth Achroia grisella. Females of this pyralid moth choose their mate based on acoustic characters of the ultrasonic calling song broadcasted by males while competing at lek. However male ultrasonic displays are very conspicuous and may attract specific predators: insectivorous bats. Therefore at leks sexual and viability selection pressures act simultaneously and can shape (1) the evolution of female mate choice, (2) the maintenance and evolution of lekking, (3) the origin of sexual acoustic communication. Taken as a whole this work emphasises the relevance of the study of selective interplays between viability and sexual selections in order to improve our understanding of how natural selection may shape the origin, evolution and maintenance of sexual traits. In particular results indicate the crucial role played by predation pressure within these evolutionary processes.

O presente trabalho se propõe a compreender a variabilidade cultural humana em relação à organização da família por meio das teorias darwinianas da seleção natural e da seleção sexual, e se encontra baseado em evidências vindas da comparação de dados etnográficos. Pretende-se demonstrar que existe uma alteração marcante no comportamento de todos os envolvidos nas relações familiares quando mudam as regras de herança. Essas alterações assim ocorrem porque as regras de herança direcionam o Investimento Parental Masculino (MPI), ora ao sobrinho, ora ao filho. A hipótese apresentada é a de que a variação do MPI modifica de maneira compreensível e previsível as relações familiares em organizações matrilineares e patrilineares. A prova da hipótese será feita por meio da aplicação do método intercultural com pesquisa etnográfica nos bancos de dados do HRAF, e utilizando-se da amostra PSF. Os resultados do presente trabalho indicarão que em sociedades em que o tio tem uma relação afetuosa com seu sobrinho, o marido espanca a mulher; e quando o pai se relaciona de maneira indulgente e amigável com seu filho, irmãos e irmãs se evitam, alinhando esses fatos de maneira que possam ser coerentemente entendidos com a teoria sociobiológica. A riqueza cultural, o sem número de costumes, as tradições, os tabus, as normas explícitas ou ocultas, os aparatos de coerção de toda sorte, as regras sobre herança, casamento, dote, preço da noiva, divisão de trabalho, enfim, todas as regras observadas em todos os agrupamentos humanos podem ser explicadas à luz das seguintes teorias: a) da “seleção de consangüíneos” (Hamilton, 1963), b) do “altruísmo recíproco” (Trivers, 1971), c) do “investimento parental e seleção sexual” (Trivers, 1972), e d) do “conflito entre prole e parentais” (Trivers, 1974). / The present work proposes to account for cultural variability in connection to human family organization, through Darwin’s theories of natural selection and sexual selection. It is also founded on evidence based on the comparison of ethnographic data of diverse human societies. It intends to demonstrate that there is a significant alteration in the behavior of family members when the rules of inheritance of wealth change. These alterations are triggered because the rules of inheritance dictate the MPI – Male Parental Investment – sometimes in the nephew and sometimes in the son. The hypothesis is that this variation in MPI (male investment in either the nephew or the son) modifies family relations in matrilineal and patrilineal organizations in a predictable manner. The role played by MPI in determining family tensions will be shown by applying cross cultural analysis to the data obtained from HRAF (Human Relations Area Files), using PSF (Probability Sample Files). The results of the present work show that societies in which the uncle’s relation with his nephew is affectionate, the husband beats the wife; on the other hand, when the father’s relation with his son is indulgent and friendly, brother and sister avoid each other. This variability of behavior can be coherently explained by sociobiological theory. Cultural wealth: the innumerable customs, the traditions, the taboos, the manifest and hidden norms, the apparatus of coercion, the rules of inheritance, marriage, dowry, bride price, the division of labor, in short, all the rules observed in all human groups can be explained in the light of the following theories: a) ‘kinship selection’ (Hamilton, 1963); b) ‘reciprocal altruism’ (Trivers, 1971; Axelrod, 1981); c) ‘parental investment and sexual selection’ (Trivers, 1972); and d) ‘parentoffspring conflict’ (Trivers, 1974).

Sexual ornaments important for mating success in many species are often assumed to evolve as condition-dependent signals of individual quality. Ornament expression can be associated with age and survival, thereby signalling individual viability. Here, we have tested viability signalling function of tail streamers and their importance for within-pair and extra-pair fertilisation success in the European barn swallow (Hirundo rustica rustica). In contrast to previous studies on this subspecies, our data suggest that tail length is not associated with fertilisation success in our population. Instead, the most important predictors of within-pair and extra-pair fertilisation success were female and male age, respectively. Our data supported viability signalling function of male tail streamers, as documented by age-related within- individual increase in their length. There was no evidence for senescence in this trait. Contrary to some previous studies, the viability signalling function of tail streamers was further supported by observed selective disappearance of males with shorter tails. Several physiological mechanisms have been proposed as maintaining signalling honesty. Among them, oxidative stress from highly reactive species (RS), including free radicals, attracted a considerable attention. Given...

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