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1er juin 2018

Aquatic insect functional diversity and nutrient content in urban streams in a medium‐sized city [Ecosphere]

Keywords : aquatic insects, functional feeding groups, medium‐sized city, nitrogen, phosphorus, urbanization

Aquatic insects play a large role in the processing of organic matter in headwater streams ; however, anthropogenic disturbances associated with watershed urbanization can impact the biodiversity and abundance of these insects. Aquatic insects function on multiple trophic levels (i.e., shredders, collectors, scrapers, and predators) and interact in the nutrient cycling within lotic systems. The degradation or loss of any of these functional groups could disrupt stream biogeochemistry and the flow of energy in stream ecosystems. We used a paired reach site design to assess the insect functional group representation in five streams impacted by urbanization with downstream urban and upstream rural reach sites. We also sampled two non‐urban reference streams with rural upstream and rural downstream reach sites.(...)

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1er juin 2018

Ericoid mycorrhizal fungi and their genomes : another side to the mycorrhizal symbiosis ? [New Phytologist]

Keywords : CAZymes, effector proteins, endophytes, ericoid mycorrhiza (ERM), genome evolution

Le génome d’un organisme porte la signature de son mode de vie, et les organismes ayant des stratégies de vie similaires devraient partager des traits génomiques communs. En effet, les champignons mycorhiziens ectomycorhiziens et arbusculaires partagent certains caractères génomiques, tels que l’expansion de familles de gènes codant pour de petites protéines sécrétées spécifiques aux taxons, qui sont des effecteurs candidats dans la symbiose, et un très petit répertoire d’enzymes dégradant les parois des cellules végétales. Une grande famille de gènes codant pour des effecteurs candidats a également été révélée chez des mycorhizes mycorhiziens (ERM) ascomycètes, mais ces génomes fongiques sont caractérisés par un très grand nombre de gènes codant pour des enzymes de dégradation agissant principalement sur les composants des parois cellulaires végétales. Nous suggérons que la signature génomique des champignons ERM reflète une stratégie de vie polyvalente, qui leur permet d’occuper plusieurs niches écologiques.

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1er juin 2018

Caught in the web : Spider web architecture affects prey specialization and spider–prey stoichiometric relationships [Ecology and Evolution]

Keywords : ecological stoichiometry, food webs, nitrogen, phosphorus, predator–prey interactions, spider webs, threshold elemental ratio

Quantitative approaches to predator–prey interactions are central to understanding the structure of food webs and their dynamics. Different predatory strategies may influence the occurrence and strength of trophic interactions likely affecting the rates and magnitudes of energy and nutrient transfer between trophic levels and stoichiometry of predator–prey interactions. Here, we used spider–prey interactions as a model system to investigate whether different spider web architectures—orb, tangle, and sheet‐tangle—affect the composition and diet breadth of spiders and whether these, in turn, influence stoichiometric relationships between spiders and their prey.(...)

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1er juin 2018

The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps [Nature]

Keywords : herpetology, palaeontology, phylogenetics

Modern squamates (lizards, snakes and amphisbaenians) are the world’s most diverse group of tetrapods along with birds and have a long evolutionary history, with the oldest known fossils dating from the Middle Jurassic period—168 million years ago. The evolutionary origin of squamates is contentious because of several issues : (1) a fossil gap of approximately 70 million years exists between the oldest known fossils and their estimated origin ; (2) limited sampling of squamates in reptile phylogenies ; and (3) conflicts between morphological and molecular hypotheses regarding the origin of crown squamates. Here we shed light on these problems by using high-resolution microfocus X-ray computed tomography data from the articulated fossil reptile Megachirella wachtleri (Middle Triassic period, Italian Alps). We also present a phylogenetic dataset, combining fossils and extant taxa, and morphological and molecular data. We analysed this dataset under different optimality criteria to assess diapsid reptile relationships and the origins of squamates.(...)

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31 mai 2018

Towards a Dynamic Interaction Network of Life to unify and expand the evolutionary theory [BMC Biology]

Keywords : evolutionary biology, interactions, theoretical biology, Tree of Life, Web of Life

The classic Darwinian theory and the Synthetic evolutionary theory and their linear models, while invaluable to study the origins and evolution of species, are not primarily designed to model the evolution of organisations, typically that of ecosystems, nor that of processes. How could evolutionary theory better explain the evolution of biological complexity and diversity ? Inclusive network-based analyses of dynamic systems could retrace interactions between (related or unrelated) components. This theoretical shift from a Tree of Life to a Dynamic Interaction Network of Life, which is supported by diverse molecular, cellular, microbiological, organismal, ecological and evolutionary studies, would further unify evolutionary biology.

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