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18 janvier 2018

Evidence for dispersal syndromes in freshwater fishes [Proceedings of the Royal Society B - Biological Sciences]

Keywords : dispersal ability, life-history strategies, ecological specialization, co-adaptation, evolutionary trade-offs, repeatability

Dispersal is a fundamental process defining the distribution of organisms and has long been a topic of inquiry in ecology and evolution. Emerging research points to an interdependency of dispersal with a diverse suite of traits in terrestrial organisms, however the extent to which such dispersal syndromes exist in freshwater species remains uncertain. Here, we test whether dispersal in freshwater fishes (1) is a fixed property of species, and (2) correlates with life-history, morphological, ecological and behavioural traits, using a global dataset of dispersal distances collected from the literature encompassing 116 riverine species and 196 locations.(...)

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17 janvier 2018

Immunogenetic novelty confers a selective advantage in host–pathogen coevolution [PNAS]

Keywords : host–pathogen coevolution, Red Queen coevolution, major histocompatibility complex, Poecilia reticulata, frequency-dependent selection

The major histocompatibility complex (MHC) is crucial to the adaptive immune response of vertebrates and is among the most polymorphic gene families known. Its high diversity is usually attributed to selection imposed by fast-evolving pathogens. Pathogens are thought to evolve to escape recognition by common immune alleles, and, hence, novel MHC alleles, introduced through mutation, recombination, or gene flow, are predicted to give hosts superior resistance. Although this theoretical prediction underpins host–pathogen “Red Queen” coevolution, it has not been demonstrated in the context of natural MHC diversity. Here, we experimentally tested whether novel MHC variants (both alleles and functional “supertypes”) increased resistance of guppies (Poecilia reticulata) to a common ectoparasite (Gyrodactylus turnbulli).(...)

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16 janvier 2018

Sexual antagonism and the instability of environmental sex determination [Nature Ecology & Evolution]

Keywords : evolutionary genetics, evolutionary theory

The sex of an organism can be determined by its genetics or its early environment. Across the animal kingdom, genetic sex determination (GSD) is far more common than environmental sex determination (ESD). Here, we propose an explanation for this pattern : the coupling of genes that bias offspring sex ratios towards one sex with genes that are beneficial in that sex but costly in the other. Gradual strengthening of the sex-specific tendency of this association eventuates in a neo-sex chromosome ; that is, GSD. Our model predicts to which system of heterogamety ESD will evolve when nesting behaviour is an important determinant of brood sex ratios. It explains the puzzling observation in some GSD species of sex reversal induced by extreme environments. The model also suggests an approach to discovering sex-determining genes in ESD species.

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16 janvier 2018

Time to re-think fungal ecology ? Fungal ecological niches are often prejudged [New Phytologist]

Keywords : endophyte, evolutionary trajectories, fungal ecological niches ; fungal genomics, molecular tools, mycorrhiza, niche variation, plant fungome

There is growing evidence that many fungi have more complex niches than previously imagined, and two articles in this issue of New Phytologist, based on different methodological approaches (Lofgren et al., pp. 1203–1212 ; Martino et al., pp. 1213–1229), support this. Both question whether the ability to colonize several ecological niches is a common phenomenon in fungi.(...)

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16 janvier 2018

The rate of telomere loss is related to maximum lifespan in birds [Philosophical Transactions of the Royal Society B - Biological Science]

Keywords : telomeres, bird, lifespan, ageing, senescence, comparative analysis

Telomeres are highly conserved regions of DNA that protect the ends of linear chromosomes. The loss of telomeres can signal an irreversible change to a cell’s state, including cellular senescence. Senescent cells no longer divide and can damage nearby healthy cells, thus potentially placing them at the crossroads of cancer and ageing. While the epidemiology, cellular and molecular biology of telomeres are well studied, a newer field exploring telomere biology in the context of ecology and evolution is just emerging. With work to date focusing on how telomere shortening relates to individual mortality, less is known about how telomeres relate to ageing rates across species. Here, we investigated telomere length in cross-sectional samples from 19 bird species to determine how rates of telomere loss relate to interspecific variation in maximum lifespan.(...)

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