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19 octobre 2016

Bushmeat hunting and extinction risk to the world’s mammals [Royal Society Open Science]

Keywords : wild, meat, bushmeat, hunting, mammals, extinction

Terrestrial mammals are experiencing a massive collapse in their population sizes and geographical ranges around the world, but many of the drivers, patterns and consequences of this decline remain poorly understood. Here we provide an analysis showing that bushmeat hunting for mostly food and medicinal products is driving a global crisis whereby 301 terrestrial mammal species are threatened with extinction. Nearly all of these threatened species occur in developing countries where major coexisting threats include deforestation, agricultural expansion, human encroachment and competition with livestock.(...)

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14 octobre 2016

Detection of human adaptation during the past 2000 years [Science]

Detection of recent natural selection is a challenging problem in population genetics. Here we introduce the Singleton Density Score (SDS), a method to infer very recent changes in allele frequencies from contemporary genome sequences. Applied to data from the UK10K Project, SDS reflects allele frequency changes in the ancestors of modern Britons during the past 2,000-3,000 years. We see strong signals of selection at lactase and the MHC, and in favor of blond hair and blue eyes. For polygenic adaptation we find that recent selection for increased height has driven allele frequency shifts across most of the genome. Moreover, we identify shifts associated with other complex traits, suggesting that polygenic adaptation has played a pervasive role in shaping genotypic and phenotypic variation in modern humans.

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14 octobre 2016

Genetic drift, selection and the evolution of the mutation rate [Nature Reviews Genetics]

Keywords : evolutionary genetics, experimental evolution, genetic variation, genome evolution, mutagenesis, mutation, next-generation sequencing

As one of the few cellular traits that can be quantified across the tree of life, DNA-replication fidelity provides an excellent platform for understanding fundamental evolutionary processes. Furthermore, because mutation is the ultimate source of all genetic variation, clarifying why mutation rates vary is crucial for understanding all areas of biology. A potentially revealing hypothesis for mutation-rate evolution is that natural selection primarily operates to improve replication fidelity, with the ultimate limits to what can be achieved set by the power of random genetic drift. This drift-barrier hypothesis is consistent with comparative measures of mutation rates, provides a simple explanation for the existence of error-prone polymerases and yields a formal counter-argument to the view that selection fine-tunes gene-specific mutation rates.

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14 octobre 2016

Below-ground frontiers in trait-based plant ecology [New Phytologist/Review]

Keywords : community assembly, comparative ecology, ecosystem processes, fine roots, functional trait, mycorrhiza, nutrient acquisition, soil carbon

Trait-based approaches have led to significant advances in plant ecology, but are currently biased toward above-ground traits. It is becoming clear that a stronger emphasis on below-ground traits is needed to better predict future changes in plant biodiversity and their consequences for ecosystem functioning. Here I propose six ‘below-ground frontiers’ in trait-based plant ecology, with an emphasis on traits governing soil nutrient acquisition : redefining fine roots ; quantifying root trait dimensionality ; integrating mycorrhizas ; broadening the suite of root traits ; determining linkages between root traits and abiotic and biotic factors ; and understanding ecosystem-level consequences of root traits. Focusing research efforts along these frontiers should help to fulfil the promise of trait-based ecology : enhanced predictive capacity across ecological scales.

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14 octobre 2016

Slow decomposition of leaf litter from mature Fagus sylvatica trees promotes offspring nitrogen acquisition by interacting with ectomycorrhizal fungi [Journal of Ecology]

Keywords : below-ground N cycling, ectomycorrhizal fungi, Fagus sylvatica, leaf litter decomposability, microbial biomass N, microcosm experiment

1. Leaf litter chemistry and ectomycorrhizal (ECM) fungi are key drivers of the below-ground nitrogen (N) cycling within forest ecosystems. Their combined effects on litter decomposition and N competition between microbial decomposers and plants are still uncertain.
2. We conducted a glasshouse microcosm experiment with low or high ECM-colonized beech (Fagus sylvatica) saplings, growing with litter collected from old or young beech trees growing on the same loamy soil. After 6 months of growth, we investigated litter decomposition rates, microbial respiration and the N pools within leaf litter, soil (different pools), microbial and plant shoot biomass.(...)

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