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5 mai 2017

Are food web structures well represented in isotopic spaces ? [Functional Ecology]

Keywords : connectance, isotopic functional indices, niche model, omnivory, virtual ecology

1.Isotopic analyses are increasingly used to assess the structure of food webs and a series of isotopic functional indices have been proposed in the last decade to characterize this structure. These indices are based on the foundational assumption that proximity in the isotopic space informs on trophic similarity between species. While it has been recognized for long that this simplifying assumption should be used with caution, no formal evaluation of its domain of validity has been performed to date.
2.We here simulate a large number (15,000) of food webs with varying characteristics to assess i) whether isotopic distance is a good proxy of trophic dissimilarity ; ii) whether isotopic functional indices are good proxies of trophic functional properties ; and iii) how the quality of these two proxies depend on various species and food web properties.(...)

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5 mai 2017

Reconciling controversies about the ‘global warming hiatus’ [Nature]

Keywords : projection and prediction, attribution, communication

Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the ‘global warming hiatus’, caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of ‘hiatus’ and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.

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4 mai 2017

Linking speciation to extinction : Diversification raises contemporary extinction risk in amphibians [Evolution Letters]

Keywords : amphibia, diversification, extinction risk, IUCN, peripatry, speciation rate, species longevity

Many of the traits associated with elevated rates of speciation, including niche specialization and having small and isolated populations, are similarly linked with an elevated risk of extinction. This suggests that rapidly speciating lineages may also be more extinction prone. Empirical tests of a speciation-extinction correlation are rare because assessing paleontological extinction rates is difficult. However, the modern biodiversity crisis allows us to observe patterns of extinction in real time, and if this hypothesis is true then we would expect young clades that have recently diversified to have high contemporary extinction risk. Here, we examine evolutionary patterns of modern extinction risk across over 300 genera within one of the most threatened vertebrate classes, the Amphibia.(...)

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4 mai 2017

General and species-specific impacts of a neonicotinoid insecticide on the ovary development and feeding of wild bumblebee queens [Proceedings of the Royal Society B - Biological Sciences]

Keywords : bumble bee queens, insect pollinator, insecticide toxicity, neonicotinoid insecticide, parasites, sublethal effects

Bumblebees are essential pollinators of crops and wild plants, but are in decline across the globe. Neonicotinoid pesticides have been implicated as a potential driver of these declines, but most of our evidence base comes from studies of a single species. There is an urgent need to understand whether such results can be generalized across a range of species. Here, we present results of a laboratory experiment testing the impacts of field-relevant doses (1.87–5.32 ppb) of the neonicotinoid thiamethoxam on spring-caught wild queens of four bumblebee species : Bombus terrestris, B. lucorum, B. pratorum and B. pascuorum.(...)

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4 mai 2017

Effects of anthropogenic disturbances on α and β diversity of fish assemblages and their longitudinal patterns in subtropical streams, China [Ecology of Freshwater Fish]

Keywords : anthropogenic disturbance, headwater stream, upstream–downstream pattern, α and β diversity

Identifying the spatial patterns of α and β diversity of biotics is an important yet little-understood area of basic and applied ecological research. Although the upstream–downstream patterns of α diversity of stream fishes are numerously reported, β diversity has received less attention. In this study, we surveyed fishes along the upstream–downstream gradients in three headwater streams of the Qingyi River, China, which were affected by different extents of human activities. We aimed to assess how anthropogenic disturbances affect α and β diversity of stream fishes and their upstream–downstream patterns.(...)

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