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7 septembre 2018

Evolutionarily distinct amphibians are disproportionately lost from human‐modified ecosystems [Ecology Letters]

Keywords : diversification, extinction risk, forests, global change, grasslands, habitat loss, land conversion, phylogenetic diversity

Humans continue to alter terrestrial ecosystems, but our understanding of how biodiversity responds is still limited. Anthropogenic habitat conversion has been associated with the loss of evolutionarily distinct bird species at local scales, but whether this evolutionary pattern holds across other clades is unknown. We collate a global dataset on amphibian assemblages in intact forests and nearby human‐modified sites to assess whether evolutionary history influences susceptibility to land conversion. We found that evolutionarily distinct amphibian species are disproportionately lost when forested habitats are converted to alternative land‐uses.(...)

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7 septembre 2018

Life stage‐specific, stochastic environmental effects overlay density dependence in an Atlantic salmon population [Ecology of Freshwater Fish]

Keywords : density independence, environmental variability, exploitation, fisheries, long‐term data, population dynamics

Atlantic salmon populations appear to fluctuate stochastically through time. It is suspected that both density‐dependent and density‐independent factors cause these fluctuations but the relative importance of each, and the life stages at which they operate, is not well known. In this study, a long‐term data set on Atlantic salmon migrants returning to the Foyle catchment, Ireland, was used to determine the role of density‐dependent and life stage‐specific environmental factors regulating population size.A Ricker density‐dependent model showed that spawning adult population size significantly predicted variation in the resultant filial generation ; however, a large amount of variation (ca. 68%) remained unexplained.(...)

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7 septembre 2018

Direct and indirect effects of chemical contaminants on the behaviour, ecology and evolution of wildlife [Proceedings of the Royal Society B - Biological Sciences]

Keywords : behavioural ecology, endocrine-disrupting chemicals, predator-prey dynamics, plasticity, sublethal

Chemical contaminants (e.g. metals, pesticides, pharmaceuticals) are changing ecosystems via effects on wildlife. Indeed, recent work explicitly performed under environmentally realistic conditions reveals that chemical contaminants can have both direct and indirect effects at multiple levels of organization by influencing animal behaviour. Altered behaviour reflects multiple physiological changes and links individual- to population-level processes, thereby representing a sensitive tool for holistically assessing impacts of environmentally relevant contaminant concentrations. Here, we show that even if direct effects of contaminants on behavioural responses are reasonably well documented, there are significant knowledge gaps in understanding both the plasticity (i.e. individual variation) and evolution of contaminant-induced behavioural changes. We explore implications of multi-level processes by developing a conceptual framework that integrates direct and indirect effects on behaviour under environmentally realistic contexts.(...)

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7 septembre 2018

A test of the cumulative effect of river weirs on downstream migration success, speed and mortality of Atlantic salmon (Salmo salar) smolts : An empirical study [Ecology of Freshwater Fish]

Keywords : downstream migration, habitat fragmentation, river barriers, Salmo salar, survival

This study investigated the cumulative impact of weirs on the downstream migration of wild Atlantic salmon (Salmo salar) smolts in the River Foyle, Northern Ireland. In spring of 2013 fish were released in two tributaries of similar length ; one tributary (impacted) had seven low‐head weirs along the migration pathway and the other was devoid of such structures (un‐impacted). Salmon smolts fitted with acoustic transmitters were monitored via a passive acoustic telemetry array during downstream migration. In 2014 the study was repeated only in the impacted tributary. Overall freshwater survival rates were high (>94%). There was no significant difference in mortality, movement pattern, delay or travel speeds between rivers or between years at any phase of migration.(...)

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7 septembre 2018

Evolutionary history of plant hosts and fungal symbionts predicts the strength of mycorrhizal mutualism [Communications Biology]

Monique Gardes

Most plants engage in symbioses with mycorrhizal fungi in soils and net consequences for plants vary widely from mutualism to parasitism. However, we lack a synthetic understanding of the evolutionary and ecological forces driving such variation for this or any other nutritional symbiosis. We used meta-analysis across 646 combinations of plants and fungi to show that evolutionary history explains substantially more variation in plant responses to mycorrhizal fungi than the ecological factors included in this study, such as nutrient fertilization and additional microbes. Evolutionary history also has a different influence on outcomes of ectomycorrhizal versus arbuscular mycorrhizal symbioses ; the former are best explained by the multiple evolutionary origins of ectomycorrhizal lifestyle in plants, while the latter are best explained by recent diversification in plants ; both are also explained by evolution of specificity between plants and fungi. These results provide the foundation for a synthetic framework to predict the outcomes of nutritional mutualisms.

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