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4 septembre 2017

Formation and Shaping of the Antirrhinum Flower through Modulation of the CUP Boundary Gene [Current Biology]

Boundary domain genes, expressed within or around organ primordia, play a key role in the formation, shaping, and subdivision of planar plant organs, such as leaves. However, the role of boundary genes in formation of more elaborate 3D structures, which also derive from organ primordia, remains unclear. Here we analyze the role of the boundary domain gene CUPULIFORMIS (CUP) in formation of the ornate Antirrhinum flower shape.(...)

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31 août 2017

Behavior and season affect crayfish detection and density inference using environmental DNA [Ecology and Evolution]

Keywords : american signal crayfish, aquatic invertebrates, environmental DNA, invasives, quantitative PCR

Although the presence/absence of aquatic invertebrates using environmental DNA (eDNA) has been established for several species, inferring population densities has remained problematic. The invasive American signal crayfish, Pacifastacus leniusculus (Dana), is the leading cause of decline in the UK’s only native crayfish species, Austropotamobius pallipes (Lereboullet). Methods to detect species at low abundances offer the opportunity for the early detection, and potential eradication, of P. leniusculus before population densities reach threatening levels in areas occupied by A. pallipes. Using a factorial experimental design with aquaria, we investigated the impacts of biomass, sex ratio, and fighting behavior on the amount of eDNA released by P. leniusculus, with the aim to infer density per aquarium depending on treatments. The amount of target eDNA in water samples from each aquarium was measured using the quantitative Polymerase Chain Reaction.(...)

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30 août 2017

Chromosomal inversion differences correlate with range overlap in passerine birds [Nature Ecology & Evolution]

Keywords : evolutionary theory, phylogenetics, speciation

Chromosomal inversions evolve frequently but the reasons for this remain unclear. We used cytological descriptions of 411 species of passerine birds to identify large pericentric inversion differences between species, based on the position of the centromere. Within 81 small clades comprising 284 of the species, we found 319 differences on the 9 largest autosomes combined, 56 on the Z chromosome, and 55 on the W chromosome. We also identified inversions present within 32 species. Using a new fossil-calibrated phylogeny, we examined the phylogenetic, demographic and genomic context in which these inversions have evolved.(...)

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30 août 2017

Unexpected changes in community size structure in a natural warming experiment [Nature Climate Change]

Subject terms : climate-change ecology, ecological modelling, ecosystem ecology, food webs, freshwater ecology

Natural ecosystems typically consist of many small and few large organisms. The scaling of this negative relationship between body mass and abundance has important implications for resource partitioning and energy usage. Global warming over the next century is predicted to favour smaller organisms, producing steeper mass–abundance scaling and a less efficient transfer of biomass through the food web5. Here, we show that the opposite effect occurs in a natural warming experiment involving 13 whole-stream ecosystems within the same catchment, which span a temperature gradient of 5–25 °C. We introduce a mechanistic model that shows how the temperature dependence of basal resource carrying capacity can account for these previously unexpected results. If nutrient supply increases with temperature to offset the rising metabolic demand of primary producers, there will be sufficient resources to sustain larger consumers at higher trophic levels. These new data and the model that explains them highlight important exceptions to some commonly assumed ‘rules’ about responses to warming in natural ecosystems.

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30 août 2017

Population extinctions can increase metapopulation persistence [Nature Ecology & Evolution]

Keywords : ecological modelling, population dynamics, theoretical ecology

Metapopulations persist when local populations are rapidly recolonized following local extinctions. Such persistence requires asynchrony ; simultaneous crashes of all populations would leave no source of recolonization. We show theoretically and experimentally that catastrophic population extinctions themselves can promote metapopulation persistence, by preventing spatial synchrony and thus enhancing recolonization. We refer to this behaviour as the ‘spatial hydra effect’ : as with the mythical hydra that grows two new heads when one is removed, extinctions can increase recolonization. The effect is robust, occurring in a wide range of theoretical models exhibiting cyclic or quasi-cyclic population dynamics. In a laboratory microcosm experiment using cyclic protist predator–prey metapopulations, catastrophic perturbations wiping out populations but leaving the patch otherwise unchanged increased metapopulation persistence when high dispersal rates would otherwise have led to spatially synchronous extinctions of all populations. We discuss several candidate examples of the spatial hydra effect in nature.

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