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4 janvier 2017

Non-native introductions influence fish body size distributions within a dryland river [Ecosphere]

Keywords : biodiversity–ecosystem function, invasive species, Lower Colorado River Basin, response–effect traits, Verde River

A contemporary challenge in ecology is assessing the ecosystem effects of multispecies introductions. Quantifying shifts in body sizes, a common trait with which many per capita rates of ecosystems functioning scales, provide an important way forward. Evidence suggests that freshwater fish introductions have altered species-level body size distributions globally, but it is difficult to interpret their functional consequences because animals contribute to ecosystem functioning at the individual level at smaller spatial scales. In this study, we determine whether these macroecological patterns hold for individual size distributions (ISDs) at local scales.(...)

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4 janvier 2017

Enclosed nests may provide greater thermal than nest predation benefits compared with open nests across latitudes [Functional Ecology]

Keywords : growth, life history, nest predation, nest structure, thermal benefits, temperate, tropical

1.Nest structure is thought to provide benefits that have fitness consequences for several taxa. Traditionally, reduced nest predation has been considered the primary benefit underlying evolution of nest structure, whereas thermal benefits have been considered a secondary or even non-existent factor. Yet, the relative roles of these factors on nest structures remain largely unexplored.
2.Enclosed nests have a constructed or natural roof connected to sides that allow a restricted opening or tube entrance that provides cover in all directions except the entrance, whereas open nests are cups or platforms that are open above. We show that construction of enclosed nests is more common among songbirds (Passeriformes) in tropical and southern hemisphere regions than in north temperate regions. This geographic pattern may reflect selection from predation risk, under long-standing assumptions that nest predation rates are higher in southern regions and that enclosed nests reduce predation risk compared with open cup nests. We therefore compared nest predation rates between enclosed versus open nests in 114 songbird species that do not nest in tree holes among five communities of coexisting birds, and for 205 non-hole-nesting species from the literature, across northern temperate, tropical, and southern hemisphere regions.(...)

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4 janvier 2017

Damming Fragments Species Ranges and Heightens Extinction Risk [Conservation Letters]

Stephanie R. Januchowski-Hartley, Céline Jézéquel, Pablo A. Tedesco

Tropical rivers are experiencing an unprecedented boom in dam construction. Despite rapid dam expansion, knowledge about the ecology of tropical rivers and the implications of existing and planned dams on freshwater-dependent species remains limited. Here we evaluate fragmentation of fish species ranges, considering current and planned dams of the Magdalena River basin, Colombia. We quantify the relationship between species range and body size and use a vulnerability limit set by this relationship to explore the influence that fragmentation of species ranges has on extinction risk. We find that both existing and planned dams fragment most fish species ranges splitting, them into more vulnerable populations. Importantly, we find that migratory species, and those that support fisheries, are most affected by fragmentation. Our results highlight the dramatic impact that dams can have on freshwater fishes and offer insights into species extinction risk for data-limited regions.

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20 décembre 2016

Global loss of avian evolutionary uniqueness in urban areas [Global Change Biology]

Keywords : biodiversity, biotic homogenization, birds, evolutionary distinctiveness, human-induced environmental change, urban ecology

Urbanization, one of the most important anthropogenic impacts on Earth, is rapidly expanding worldwide. This expansion of urban land-covered areas is known to significantly reduce different components of biodiversity. However, the global evidence for this effect is mainly focused on a single diversity measure (species richness) with a few local or regional studies also supporting reductions in functional diversity. We have used birds, an important ecological group that has been used as surrogate for other animals, to investigate the hypothesis that urbanization reduces the global taxonomical and/or evolutionary diversity. We have also explored whether there is evidence supporting that urban bird communities are evolutionarily homogenized worldwide in comparison with nonurban ones by means of using evolutionary distinctiveness (how unique are the species) of bird communities.(...)

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20 décembre 2016

Investigating uncertainties in zooplankton composition shifts under climate change scenarios in the Mediterranean Sea [Ecography]

Ensemble niche modelling has become a common framework to predict changes in assemblages composition under climate change scenarios. The amount of uncertainty generated by the different components of this framework has rarely been assessed. In the marine realm forecasts have usually focused on taxa representing the top of the marine food-web, thus overlooking their basal component : the plankton. Calibrating environmental niche models at the global scale, we modelled the habitat suitability of 106 copepod species and estimated the dissimilarity between present and future zooplanktonic assemblages in the surface Mediterranean Sea.(...)

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