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Dominance status in female ring-tailed lemurs (Lemur catta) has a pervasive effect upon social organization, however the proximate mechanisms underlying female rank-relations remain poorly understood. I investigated how four such attributes - weight, age, agonistic frequency, and fecal testosterone levels - relate to female rank-order wild ring-tailed lemurs at the Beza Mahafaly Special Reserve, Madagascar. My results indicated that: (1) The mean weight of high-ranking females is significantly greater than in lower-ranking females; (2) The relationship of age in relation to rank follows an inverted J-shaped pattern, with old adults attaining the highest average rank, followed by prime adults, young adults, and very old adults; (3) Significant, positive correlations between rank and rates of agonism exist in four of the six study groups; and (4) The effect of rank on mean testosterone concentration was significant in one social troop, in which the two highest ianking females exhibited significantly lower mean testosterone levels.

A Madagascar, pendant longtemps les zones rurales malgaches présentaient toutes les caractéristiques favorables à une forte fécondité. Récemment encore l’idée que les enfants génèrent pour les parents des bénéfices supérieurs aux coûts était largement partagée par tous. Les enquêtes démographiques montrent bien que si la fécondité en milieu rural reste plus élevée qu’en milieu urbain (en 2003, l’ISF y était de 5,7 enfants par femme en milieu rural et de 4,0 enfants en milieu urbain), elles montrent aussi que la fécondité en milieu rural malgache commence à diminuer. L’indice synthétique de fécondité du milieu rural est passé de 6,7 enfants par femme en 1997 à 5,7 enfants par femme en 2003. Cette baisse de la fécondité est observée sans changement socio-économique important. La pauvreté rurale reste élevée et elle a progressé plus vite que la pauvreté urbaine.Cette thèse se propose de présenter les modèles des transitions démographiques en milieu rural malgache, en replaçant la recherche dans le débat sur le lien entre développement économique et baisse de la fécondité qui a été remis en cause notamment dans les pays du Sud.L’analyse montre que si dans certaines provinces, le primat de l’économique est fort et que c’est bien la modernisation qui a permis la baisse de la fécondité, il existe des provinces où malgré une pauvreté persistante, voire même une aggravation de celle-ci, d’autres facteurs ont permis malgré tout des changements de fécondité. Parmi ces facteurs, l’un des plus importants est le système social qui repose sur des traditions culturelles influençant les situations démographiques. / In Madagascar, rural areas used to present all the favorable characteristics to a strong fertility. Even recently the idea that children generate superior profits than costs was widely shared. Demographic surveys show that if the fertility in rural areas stays higher than in urban areas (in 2003, ISF was 5.7 children by woman in rural areas and 4.0 children in urban areas), fertility in rural areas begins to decrease. The ISF of rural areas fell from 6.7 children by woman in 1997 to 5.7 children by woman in 2003. This fertility decline is noticed without important socioeconomic change. Poverty in rural areas remains high and even increased quicker than urban poverty.This thesis proposes to introduce demographic transitions models in Malagasy rural areas by focusing on the debate on the link between economic development and fertility decline which was notably questioned in Southern countries.The analysis shows that if in certain provinces, the central role of the economy is strong and that it’s definitely the modernization process that allowed the reduction of fertility, there are provinces where in spite of a persistent poverty and even a worsening of it, other factors allowed fertility changes. Among them, one of the most important is the social system which is based on cultural traditions influencing demographic situations.

The island continent of Madagascar spans nearly 13.5o of latitude in the SW Indian Ocean. Its coastline includes a number of well developed coral reefs, ranging from tropical Nosy Bé (NW Madagascar, 12oS) and Vohemar (Volhmarina, NE Madagascar, 13oS) to subtropical Tuléar (Toliara , SW Madagascar, 23.5oS), as well as temperate coral communities at Fort Dauphin (Tolagnaro, SE Madagascar, 25oS). Given the range of environmental conditions experienced by reef corals at these different sites, Madagascar represents an ideal location to study the distribution of algal symbionts (Symbiodinium spp.) in these coral hosts. To investigate the effect of latitudinal gradients in temperature on Symbiodinium distributions, 220 samples from 27 coral genera in 12 families were collected from these 4 sites in September 2001. To test the stability of these distributions over time, a further 337 samples were collected from the Nosy Bé and Tuléar regions in March 2007 and November 2009. Symbiodinium communities were screened using Denaturing Gradient Gel Electrophoresis (DGGE) to analyze the internal transcribed spacer-2 (ITS-2) region of Symbiodinium ribosomal DNA, with individual symbiont taxa identified by sequencing individual DGGE bands. Significant differences were found in the Symbiodinium cladal composition of reef corals at different sites, with corals at northern sites containing a higher relative frequency of Symbiodinium in clade D (occurring as mixed clade C+D communities) than southern sampling sites. Nominal logistic analysis of the distribution of symbionts found a significant effect of coral taxa and site, but not of sea surface temperature metrics (environmental data obtained from NOAA’s Coral Reef Watch satellite-derived data) in determining the distribution of different symbionts. Rarefaction analysis indicated there were no differences in Symbiodinium richness (at either the clade or the subtype level) between different sites, or between different sampling intervals. Differences existed in the subcladal composition of dominant ITS-2 types found in congeners at different latitudes, with corals in the genus Acropora being dominated by Symbiodinium C3 (specifically subtype C3z) in northern sites, and C1 in southern sites. Symbiont communities changed between 2001 and 2007/2009, with increases in mixed Symbiodinium C+D assemblages occurring at southern sites that had experienced temperature stress during the intervening period. Decreases in mixed Symbiodinium communities occurred at northern sites, which were not as severely affected by thermal stress. It is suggested that the latitudinal gradients in Symbiodinium found in Madagascar, and the environmental controls on community structure described here, provide important insight into how coral species in this understudied area can adapt or acclimatize to changing environmental conditions through shifts in the composition of their symbiont communities. This will help improve our understanding of how projected climate change in the SW Indian Ocean will affect survival trajectories for coral reefs in the region.

Thesis--Faculté des lettres de Paris, 1901. / Includes bibliographical references.

Thèse--Économie--Paris X, 1976. / Bibliogr., 2 p.

Texte remanié de: Th. doct.--Géo--Paris 10, 1991. / ORSTOM = Institut français de recherche scientifique pour le développement en coopération. En appendice, choix de documents. Bibliogr. p. 314-324.

Thèse de doctorat--Sciences naturelles--Faculté des sciences de Paris, 1912. N°: 1454. / Notes bibliogr.

Inaug.-diss.--Leipzig. / Lebenslauf. "Verzeichnis der zu der vorliegenden arbeit benutzten literatur," p. 132-144.

Th. 3e cycle--Hist. de l'Afrique--Paris 1, 1986.