Genome sequencing of the Heliconius butterfly questions mimicry theories By sequencing the genome of the tropical butterfly Heliconius melpomene, entomologists have challenged a mimicry theory. Certain toxic species in the genus Heliconius are similar in appearance, which allows them to defend themselves against predators. However, this is not only due to gradual convergence. Neighboring species can also directly exchange the genes that determine resemblance. This shows that hybridization between species can favor adaptation. Nature May 2012 online The colored patterns on the wings of the butterfly Heliconius melpomene signal their toxicity, warning off potential predators. Does biodiversity loss have an impact on humanity? -------------------------------------------------------------------------------------------------------------------------------------------------------- Along the same lines as the IPCC reports on climate change, a group of seventeen specialists met to assess the impact of today’s biodiversity loss on humans and identify areas of scientific consensus. To do this, they analyzed around 2,000 scientific papers. One of the points on which all agreed was that biodiversity loss adversely affects the functioning and stability of ecosystems. A reduction in the number of species hinders crop and forest productivity as well as the stability of fisheries production, although other ecosystem services, such as pollination and water purification by wetlands, appear less impacted. While this work will be an incentive to undertake further research, recent data suggests that the impact of biodiversity loss is comparable to that of other global changes such as climate change and excess nitrogen input from agriculture. This should help decision-makers to implement appropriate policies aimed at curbing this alarming trend. Nature June 2012 online Pigeon-hunting fish on the rampage Wels catfish are fearless. These large fish, recently introduced into the Tarn River in France, are not afraid to stick half their body out of the water to hunt pigeons at the water’s edge. Tests carried out on the catfish show that pigeons now make up a significant part of their diet. Although the reasons for this unprecedented predatory behavior remain unknown, the study shows the extraordinary adaptation of the catfish to their new environment. PLOS ONE December 2012 online How do plants take root? An international team has described one of the mechanisms whereby plant roots branch and explore new regions in the soil in search of water and nutrients. When a secondary root forms in the deep layers of the primary root, its cells draw water thanks to proteins called aquaporins, which are controlled by a plant hormone called auxin. The secondary root thus becomes strong enough to mechanically push back the cells of the primary root, emerge and reach the soil. 15 Nature Cell Biology September 2012 online Early stages of root branching. In green, a mass of small cells giving rise to a secondary root, and, in pink, the area of expression of one of the aquaporins studied. 2012 A year at CNRS
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