Showing results 1461 to 1480 on 1600 in total
Thèse de Morgane Tidière le mercredi 7 décembre 2016 à 13 h 30 - salle de conférence BU (La Doua)
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Symbiosis evolution is often viewed as a progress, with emergence of new adaptive properties. However, symbiosis also enhances the interdependence between partners. I describe several such interdependences, and emphasize that they arise without emergence of new property. Generally, when two partners permanently interact, a mutation in one partner can be complemented by the other. Independency is then lost without any positive selection, in a neutral evolution. The accumulation of such steps makes the reversion to independency unlikely, and drives interdependency in symbiosis.
Symbiosis evolution is often viewed as a progress, with emergence of new adaptive properties. However, symbiosis also enhances the interdependence between partners. I describe several such interdependences, and emphasize that they arise without emergence of new property. Generally, when two partners permanently interact, a mutation in one partner can be complemented by the other. Independency is then lost without any positive selection, in a neutral evolution. The accumulation of such steps makes the reversion to independency unlikely, and drives interdependency in symbiosis.
These d'Alexandra Popa - mardi 24 mai 2011 - 14h00 - Amphithéâtre du CNRS
Males and females of most species share nearly the entire genome, and yet they use many of their shared genes in radically different ways. Differential expression between males and females is thought to be product of conflicting male- and female-specific selection over optimal transcription, and to form the underlying basis of sexual dimorphism in many species. If the relationship between sex-biased gene expression and sexually dimorphic phenotypes is true, then several simple predictions can be made. First, altering sex-specific selection should elicit a response in sex-biased gene expression, and this response should be more pronounced for genes linked to sex chromosomes. Second, although sexual dimorphism is often envisaged as a dichotomous comparison between female and male forms, many species show more of a continuum, with some individuals occupying intermediate points along an axis of dimorphism. In these cases, the magnitude of sex-biased expression should reflect the degree of sexual dimorphism. Third, the degree of sex-biased expression should accumulate over time in response to continuous sex-specific selection. Case studies using both comparative and experimental evolutionary frameworks will be presented to address these predictions.
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Postcopulatory sexual selection is thought to be an important force driving the evolution of sperm design. Yet, despite numerous theoretical and empirical studies of the relationship between sperm design and sperm competition (as one postcopulatory sexual selection mechanism) is still poorly understood. A series of comparative studies in several taxonomic groups have found inconclusive and sometimes even contradictory results suggesting that in different taxonomic groups the evolution of sperm design in the context of sperm competition show markedly different patterns. We conducted the largest to date comparative study including over 250 species of passerine birds to investigate the relationship between sperm design and sperm competition and to determine the evolutionary rate of sperm design as a sexually selected trait. We did so in three ways: (I) we investigated the relationship between sperm design and sperm competition at different phylogenetic levels its association with the underlying phylogeny; (II) we tested the interspecific, the intraspecific and the intra-male variation of sperm design in the context of sperm competition; (III) we performed experiments to improve our understanding of the behavioural mechanisms influencing sperm design and function. Our results provide new insights into the evolution of sperm design as a sexually selected trait.
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LBBE researchers are highlighted by the journal Molecular Biology and Evolution for their contribution on the neutralist-selectionist debate
The LBBE benefits from the opening of a position of Master/Mistress of Conferences in 2022. We are looking for a profile of Biostatistician with expertise in modeling survival, excess mortality and high-dimensional data to strengthen the Biostatistics Health Team of the Department of Statistics and Modeling for Health Sciences.
More details below.
Do not hesitate to contact us.
Thèse de Marion Germain le mardi 16 décembre 2014 à 13 h 30 - amphithéâtre Déambulatoire 1 (Doua)
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